Thursday, November 10, 2011


Hiroko Tabuchi reports in The New York Times November 3, 2011 that “…the plant’s owner admitted for the first time that fuel deep inside three stricken reactors was probably continuing to experience bursts of fission. … The disclosures raise startling questions about how much remains uncertain at the plant… The presence of xenon 135 in particular, which has a half-life of just nine hours, seemed to indicate that fission took place very recently. … The jumble of material and conditions in the damaged reactors seem very unlikely to be able to produce sustained fission, but some experts have long suspected intermittent criticalities. In other accidents, nuclear material has burst into fission, but the released energy then re-arranges the damaged fuel into a configuration that no longer support (sic) fission. Gradually, the material re-forms in a way to support another burst. …Junichi Matsumoto, a Tokyo Electric spokesman, acknowledged episodes of fission, saying… ‘There is a possibility that certain conditions came together temporarily that were conducive to re-criticality,’ and that the measurements indicated a burst that occurred at a slightly higher rate than prior cases. ‘It’s not that we’ve had zero fission until now,’ Mr. Matsumoto said. ‘But at this point, we do not think there is a large-scale and self-sustained re-criticality.’ … Hiroaki Koide, assistant professor at Kyoto University’s Research Reactor Institute… [said] if episodes of fission at Fukushima were confirmed… ‘our entire understanding of nuclear safety would be turned on its head.’”

The IAEA issued a follow-up status report the day after the Times article appeared, indicating a re-criticality event was highly unlikely ( The IAEA update notes the following:
“Based on further analysis, Japanese authorities have concluded that the xenon concentrations are not due to a criticality event but rather from the spontaneous fission of curium-242 and 244. (Spontaneous fission is a form of radioactive decay that does not involve chain reactions and is characteristic of very heavy isotopes. Spontaneous fission occurs in low levels in all nuclear reactors.)
This conclusion is based on three key factors outlined and discussed in the report:
• The inventory of Cm-242 and Cm-244 was calculated as was the concentration of Xe-135, resulting from the spontaneous fission of Cm-242 and Cm-244. If nuclear fission of the reactor's uranium fuel were occurring, at the lowest possible level, the levels of xenon detected would be several orders of magnitude higher than those measured. Current levels of xenon are consistent with those that would be generated by spontaneous fission of Cm-242 and Cm-244;
• If the core had been experiencing a criticality event, the injection of boron water should have stopped the criticality and terminated the generation of xenon. However, the xenon levels were not influenced by injection of boron water into the core; and
• If the core was undergoing a criticality event the temperature and pressure readings would be expected to rise as the event would increase heat production within the core. However, the temperature and pressure levels have not undergone any significant increases either before or after xenon were detected, indicating that no criticality event is occurring.”
The issue of intermittent criticalities could certainly be clarified if TEPCO and NISA would install real time monitors at each of the four reactors that would provide minute by minute, and thus hourly data on airborne emissions. Any re-criticality incidents would create enough heat to cause increased steam emissions, which would be much more obvious and easy to monitor than the micro-emissions in the spontaneous emission of curium-242 and -244. The IAEA status report is probably correct in that no re-criticality has occurred, but it’s certainly interesting that there remains a potential for re-criticality until such time as the molten fuel actually is removed from the reactor vessels.

Further information on the re-criticality issue can be accessed at:

Also in the news is the new estimate of the time period needed to decommission the four reactors at Fukushima Daiichi. A CNN report by Junko Ogura (Tuesday November 1, 2011) quotes the Japanese Atomic Energy Commission as stating “Decommissioning… will likely take more than 30 years to complete [following cold shutdown, which is expected by the end of the year.]… Removal of debris – or nuclear fuel – should begin by the end of 2021.”

Also of note is a recent headline in Yahoo! News (October 24, 2011; “Up to 20 million tons of debris from Japan’s tsunami moving toward Hawaii”. While the Yahoo! News article provides a graphic illustration of when the debris is expected to reach the west coast, within three years or sooner, there was no mention that this debris field is likely to be highly contaminated with fallout resulting from the prevailing winds depositing Fukushima-derived radioactive contamination on the tsunami debris. Also of continuing interest is that significant hot particle fallout would accompany any contamination of the tsunami debris. For information on the nature of hot particle nuclear accident-derived contamination and its presence in the Chernobyl plumes please refer to our publication Fukushima Daiichi: Nuclear Information Handbook. See page 77 for the definition as well as the bibliographic citations of the literature pertaining to hot particle fallout from the Chernobyl accident on pages 229-232.

Thursday, October 27, 2011

Lessons learned and questions to be asked pertaining to American boiling water reactor (and pressurized water reactor) accidents

The accidents at Fukushima Daiichi represent a new paradigm in nuclear power plant accidents, where in contrast to the meltdown at Three Mile Island, emissions from melted fuel assemblies were not contained within a pressurized vessel. Given the large numbers of boiling water reactors still operating in the United States as well as in other nations, and the high risk of operating these reactors without a tertiary power backup system, failure of the primary electrical system (as happened during the recent earthquake in the Maryland area) followed by failure of the backup diesel generators is now a much more likely possible scenario than was previously recognized before the accident in Japan. Considering the key role that first responders utilizing traditional fire equipment played in mitigating the impact of the accident in Japan, all community first responders in the area of any nuclear power plant should now be training in the methodologies necessary to provide large quantities of water to cool melted fuel assemblies in an emergency situation where primary and secondary containment structures and electrical cooling capacities have been damaged or destroyed.

Question 1: are the Plymouth, Kingston, and Duxbury fire departments aware that in the event of a similar accident at the Plymouth, MA, boiling water reactor they may be called to provide services similar to those executed by the fire companies in Japan, who may have saved the day in the several weeks following the Fukushima Daiichi disaster? Are there any fire departments anywhere in the US that are preparing for this kind of emergency situation?

Question 2: With respect to the large quantities of water pumped onto the melted fuel assemblies in Japan, wouldn’t it be practical to surround each American water reactor with a series of dikes that would prevent runoff of highly contaminated accident-derived cooling water? What are the contingency plans of the US NRC, which was very proactive in proposing emergency responses to the Japan accident, for US reactors to recover highly radioactive water used to cool melted fuel assemblies during an accident?

Question 3: A lingering question pertaining to liability for damages resulting from the accident in Japan remains unresolved. General Electric’s blatantly incompetent boiling water design, discussed in the first chapter of the Fukushima Daiichi: Nuclear Information Handbook, provides an obvious legal basis for significant compensation by GE to the many communities impacted by the accident in Japan (+/- 20 billion US dollars)? Why has GE been exempt from any damage claims with respect to the vulnerability of their boiling water reactors to meltdown accidents? Given the large number of GE designed boiling water reactors in the US and the likely possibility of future fuel meltdown accidents, why should GE not set aside +/- 100 billion dollars in an escrow account to compensate future victims of a design flaw-related nuclear accident in the US?

Reduced airborne emissions

In the Wall Street Journal of October 18, 2011, Mitsuru Obe reported that TEPCO estimates airborne radiation releases are now down to 100 million Bq/hr and that steam leakage has essentially ended because all damaged reactor temperatures have recently fallen below 100 degrees Celsius. TEPCO, the Japanese government, and local first responders can be congratulated on the successful mitigation of what could have been a much larger release of accident-derived emissions considering that three reactor cores and four spent fuel pools containing 4,368 fuel assemblies suffered simultaneous meltdowns. Given the approximately 43 million curies of radiocesium in these assemblies at risk of being released in this series of accidents, the successful cooling of the fuel assemblies that melted during this series of accidents is a major step in preventing further airborne releases. Three important issues remain to be documented and resolved.
• What is the ongoing rate of emissions of water-borne discharges from the continuing efforts to cool the melted fuel assemblies and maintain temperature below the boiling point of water?
• What proportion of these water-borne discharges have been recovered, and what is the amount of radiocesium and other isotopes that the radioactive waste water filters have successfully captured?
• What is the current estimate of the total source term of the Fukushima Daiichi MIME (multiple interlocking meltdown event), including both airborne and water-borne emissions?
Since there are seven accident point sources at Fukushima Daiichi, will TEPCO and NISA be more forthcoming and issue more detailed reports on airborne emissions from all seven accident sites as well as further information about the water-borne contaminants generated at each of the four reactor sites, which will need continual cooling indefinitely?

Thursday, October 6, 2011

NRC letter from Edward Markey

I urge you to read this interesting letter sent to the NRC by Edward Markey about the challenges of hurricanes and other extreme weather to nuclear power plants.

Thursday, September 1, 2011

Catastrophe Pie Charts

The July 26 – August 12 accident emission rate estimate of 200 million Bq/hr of gross radiocesium can be contrasted with the radiocesium soil contamination survey, also released on August 29th. Gross radiocesium levels approaching 30 million Bq/meter squared in the town of Okuma provide a startling juxtaposition with the current accident emissions rate estimate. No similar levels of Chernobyl-derived radiocesium contamination were noted in 2001 when Chernobyl Fallout Data 1986 – 2001 was published. Much of this data is reproduced in Section 8 of the Davistown Museum’s Nuclear Information Handbook ( It should be noted that the Fukushima Daiichi accident source term (release inventory), probably significantly larger than the Chernobyl source term, is only one among thousands of slices of the Anthropogenic Radioactivity Pie Chart. This pie chart includes thousands of point sources ranging from weapons testing cumulative fallout (+/- 3500 Bq/square meter Cs-137) to Savannah River, the Russian Arctic, etc. The Anthropogenic Radioactivity Pie Chart is, in turn, only one slice of the Biocatastrophe Pie Chart. ( For a survey of the ongoing impact of the human ecology soap opera, blog readers are invited to visit and buy a Kindle version of the three volume Phenomenology of Biocatastrophe series and take it to the beach. Both our Fukushima Daiichi Nuclear Information Handbook and our 5 volume survey of Hand Tools in History are also available on

Provisional evaluations of current emission rate of radioactive materials from the Unit 1 to 3 at Fukushima Daiichi

As a component of the Tokyo Electric Power Company’s Roadmap towards Restoration from the Accident (as of August 29, 2011), TEPCO has provided the following information about the estimated current emission rates from all point sources.

  • March 15, 9 am – 15 pm: approx. two quadrillion Bq/hr (2.0 x 1015)

  • March 25, 0 am – March 26 11 am: approx. 2.5 trillion Bq/hr (2.5 x 1012)

  • April 4, 9 am – April 6 0 am: approx. 0.29 trillion Bq/hr (2.9 x 1012)

  • June 20 – June 28: approx. 1 billion Bq/hr (1.0 x 109)

  • July 26 – August 12: approx. 0.2 billion Bq/hr (2.0 x 108)

Any comments on these estimated accident emission rates would be appreciated. The question arises: since these emission rates derived from measurements taken at the site boundary, and there are seven emission point sources at Fukushima Daiichi, how accurate are the current release rate estimates? How do they compare with release rate estimates, which are done on a continuous basis by the National Security Agency? The July 26 – August 12 approximate estimate of 200 million Bq/hr indicates TEPCO has been successful in maintaining reduced temperatures in the melted fuel assemblies in their attempt to reach a cold shutdown status. Other TEPCO Roadmap summaries indicate significant success has been achieved in recovering and filtering fuel assembly coolant water, which is still being applied manually to avoid re-criticality. Easily accessible comprehensive analysis of the total contamination released in the form of high radiation level cooling waters is not yet available. An overview of major countermeasures undertaken at the accident site as of August 17th is available in the TEPCO Roadmap of August 29, 2011 (

Extreme soil contamination detected near Fukushima plant

The first comprehensive radiometric survey of accident-derived radiocesium contamination was released August 29, 2011.

The measurements were taken June 6 to June 14, about three months after the Great East Japan Earthquake, by 780 members of 129 universities and specialized organizations from around the nation. Soil samples were collected from about 2,200 locations to identify the concentration levels of radioactive cesium… The map shows that areas with high radiation levels are concentrated in a zone to the northwest of the plant within a 40-km radius of the facility… The finding emerged in a map published Aug. 29 that for the first time shows contamination levels of areas within a 100-km radius of the plant. One location in the town of Okuma had the highest value at about 30 million becquerels of cesium of all types per square meter. About 8 percent of the measured areas recorded more than 555,000 becquerels, the figure that required forcible relocation by residents in the 1986 Chernobyl nuclear incident… Soil samples were collected for each 2-square-km area within an 80-km radius of the plant. Samples were also collected from each 10-square-km area within an 80- to 100-km radius of the facility. The number of sample locations total five for each radius zone. The sample was drawn from the soil 5 centimeters from the surface. The concentration levels of cesium-134 and cesium-137-the half-life periods of which are two years and 30 years, respectively-were estimated as of June 14 in this project.”

The contaminated soil map legend uses the following reporting units. Concentration level of cesium-137 per square meter unit becquerel: 3 million and over; 1 million – under 3 million; 0.6 million – under 1 million; 60,000 – under 0.6 million; and 10,000 – under 60,000. (

Thursday, August 11, 2011

Japan withheld nuclear radiation data, leaving evacuees in peril

The New York Times (August 9, 2011, pg. A8) has provided a second radiometric sketch of Fukushima Daiichi-derived fallout. The source of this map, which uses the standard reporting unit for ground contamination of Bq/square meter, is cited as the Nuclear Emergency Response Headquarters Office of Japan. The Times map caption notes “A Japanese computerized early warning system started to generate maps projecting the trajectory of radiation plumes from the Fukushima Daiichi plant within hours of the accident on March 11, but none of the maps were made available to the public until nearly two weeks later. The map below shows information made available to the prime minister’s office on March 16.” This clearly indicated Japan’s capacity to accurately monitor ground contamination on an hourly basis. The plume direction on March 16th matches the direction of maximum contamination noted in the Times on August 2nd, but contamination levels are significantly less at this early stage of the accident.

One of many flies in the ointment is the IRSN (France) sketch illustrating accident-derived air contamination dispersion on March 19th, reprinted on page 33 of the Davistown Museum’s Nuclear Information Handbook. The prevailing wind on this date resulted in significant but as yet undocumented ground contamination to narrow but extensive shoreline regions ~300 kilometers north of the accident site. This additional region of contamination highlights the need for public disclosure of a systematic survey of ground contamination throughout Japan – data the Japanese government is obviously still withholding.

All Japanese and concerned world citizens should also be reminded the cumulative ground deposition of Cs-137 from weapons testing-derived fallout is significantly less than 5,000 Bq/square meter in most nations. Given the map legend of soil contamination reprinted in the Aug. 2nd New York Times, which illustrates Fukushima Daiichi-derived fallout levels below 28,000 Bq/ square foot (300,000 Bq/square meter) in white without further analysis, Japan’s Nuclear Energy Response Headquarters has a moral as well as practical obligation to provide accident fallout-derived concentrations of radiocesium in a radiometric survey range of 300,000 Bq/square meter down to at least 5,000 Bq/square meter, the upper range of cumulative weapons testing fallout. This survey must be accompanied by full disclosure of the seven multiple interlocking meltdown event (MIME) hourly emissions since the accident began. A survey of washout pathway emissions, including gallons in/gallons out, gallons in storage, filtered gallons, curies recovered, and estimated releases of the Fukushima Daiichi accident is another component that needs further documentation.

On another related topic, Alex Roslin has written an informative review of radiation levels in Canada, as tabulated in March and April by Health Canada, which “detected massive amounts of radioactive material from Fukushima in Canadian air in March and April at monitoring stations across the country. The level of radioactive iodine spiked above the federal maximum allowed limit in the air at four of the five sites where Health Canada monitors levels of specific radioisotopes… The iodine-131 level in the air in Sidney peaked at 3.6 millibecquerels per cubic metre on March 20. That’s more than 300 times higher than the background level, which is 0.01 or fewer millibecquerels per cubic metre… One of the highest post-Fukushima radiation readings in North America came on March 27 in rainwater in Boise, Idaho. It contained 14.4 becquerels of iodine-131 per litre – 130 times the U. S. Environmental Protection Agency’s maximum level of 0.11 millibecquerels per litre… But nobody seemed to investigate how long the rainwater in Boise remained radioactive. Inexplicably, the EPA stopped monitoring Boise’s rainwater after the extremely high reading on March 27. The agency’s only other reading for the city was on March 22.”

Many thanks to Ken Belson, Norimitsu Onishi, and Martin Mackler of The New York Times and Alex Roslin of for providing updates on the accident emissions from Fukushima Daiichi.

Tuesday, August 2, 2011

Soil contamination update

In an article on the attempt of a concerned citizen in Japan to make her own measurements of radioactivity contamination from the Fukushima Daiichi accident, The New York Times (August 1, 2011 pg. A1, A3) has provided the first isometric sketch of accident-derived radiocesium soil contamination that we have seen. The New York Times article republished a May 26, 2011 compilation of soil contamination levels of Cs-134 and Cs-137, in which it cites the US Department of Energy and the Japanese Ministry of Education, Culture, Sports, Science, and Technology as being the source of the data.

An anomalous characteristic of this article is the use of soil contamination reporting units expressed in becquerels per square foot instead of per square meter. One square meter contains 10.76 square feet. To compare the data in this article with the hundreds of reports of Chernobyl soil contamination, multiply the Bq/sq m by 10. Also consult the extensive Chernobyl fallout database republished in the Fukushima Daiichi: Nuclear Information Handbook.

The isometric sketch reprinted in this article shows an extensive area of contamination “279,000 or more Bq/sq ft” extending to the northwest of the accident site beyond the 18 mile radius (+/- 21 miles) towards the town of Iidate. This means that soil contamination in this area is approximately 3 million or more Bq/sq m. Maximum radiocesium contamination levels from the Chernobyl accident were +/- 5 million Bq/sq m, with contamination areas above 100,000 Bq/sq m occurring thousands of kilometers away from the accident site. The isometric map also shows contamination in the range of 93,000 to 279,000 Bq/sq ft extending +/- 26 miles to the northwest as well as approximately 6 miles to the southwest towards Shidamyo. These levels of soil contamination resulted from a brief shift in the prevailing trans-Pacific wind direction, which brought accident-derived emissions inland.

A startling aspect of this report is the use of white, rather than grays, to signify areas with contamination “less than 28,000 Bq/sq ft”. The use of the color white implies the areas outside of the gray were un-impacted, when, in fact, large areas away from the accident site have soil contamination, which may approach 300,000 Bq/sq m. During the 1960s, cumulative weapons-testing-derived radiocesium contamination peaked at less than 5,000 Bq/sq m, yet there was worldwide concern about the health physics impact of fallout in this range of soil contamination. This isometric map inadvertently graphically illustrates the need for a much more comprehensive survey of soil contamination levels throughout Japan. The Fukushima Daiichi accident scenario is complicated by the fact that undocumented emissions are still occurring from all seven accident sites. Changes in prevailing wind directions due to the advent of the rainy season also raise the possibility of additional contamination occurring throughout Japan from both ongoing emissions and re-suspended contamination.

The article in The New York Times provides the first hint that detailed soil contamination data is available and can be easily converted into isometric maps that the general public can understand. The use of 300,000 Bq/sq m (28,000 Bq/sq ft) cutoff for reporting radiocesium soil contamination is absolutely unacceptable. As a matter of both honor and practicality, a much more detailed post-rainy season survey of accident-derived contamination should be the demand of all Japanese citizens. The extensive documentation of the many radioisotopes released by the Chernobyl accident, numerous useful definitions, and a survey of protection action guidelines is easily accessible for any concerned citizen interested in the impact and evaluation of nuclear accidents in Fukushima Daiichi: Nuclear Information Handbook. This Handbook, sponsored by the Davistown Museum may be purchased through or ordered from the Davistown Museum.

The New York Times article focuses on the attempts of Japanese private citizen Kiyoko Okoshi to monitor radiation in the area of her home in Iwaki Town in response to the lack of accurate data from the Japanese government. This article may serve the useful purpose of alerting all concerned citizens to the failure of the Japanese government and TEPCO to execute comprehensive monitoring of accident emissions in the form of a survey of soil contamination levels by the indicator nuclides Cs-137 and Cs-134. The lack of this easily compiled data also emphasizes the lack of public disclosure of real time monitoring of ongoing accident emissions, which continue to occur in both the water washout pathway and as volatile airborne emissions.

Websites providing radiological monitoring data

Japanese Information Sources
Nuclear and Industrial Safety Agency (NISA); -- shows countermeasures for the Great East Japan Earthquake

Ministry of Education, Culture, Sports, Science and Technology – Japan (MEXT); -- shows radiation data collected in mainland Japan

System for Prediction of Environment Emergency Dose Information (SPEEDI); -- shows disaster prevention data

Real time Map of SPEEDI data; -- shows levels at each monitoring station, color coded

Japan Open Radiation Dashboard; -- shows graphs of radiation data by prefecture

Spreadsheet of Current Reactor Conditions; -- shows actions being taken on each reactor

Tokyo Electric Power Company (TEPCO); Status of Fukushima Daiichi and Fukushima Daini Nuclear Power Stations after Great East Japan Earthquake --

U.S. and Other Information Sources

University of California, Berkeley Nuclear Engineering Dept.; -- has data on radiation sampling in milk, rainfall, river water, and air in becquerels and equivalent dose

Institut de Radioprotection Nucleaire (IRSN); -- shows videos of the plume

Where are the Clouds?; -- A blog covering the movement and impact of the radioactive plume

EPA’s RadNet map;

Another RadNet map interface;

Black Cat Systems Online Geiger Counter Nuclear Radiation Detector Map; -- Amateur network of Geiger counters; -- another amateur Geiger counter network

Oregon State Department of Health Monitoring Data; -- Updated daily

Texas A&M Plume Trajectory Projections;

MIT Nuclear Information Hub;

AREVA North America: Next Energy Blog;

Health Canada: Radiation Monitoring Data;

Please email us at: with additional suggestions about other sources of information on Fukushima releases and plume pathways.

Thursday, July 28, 2011

Fukushima Daiichi Information Distribution Restrictions

The Davistown Museum is having difficulty contacting for the purpose of having the Nuclear Information Handbook available and for sale in Japan. Assistance from any interested visitors to this blog would be welcomed.

We also haven't heard back from any of the Japanese media we have contacted about a variety of questions we have about the Fukushima Daiichi accident, its current status, or the irregularities in the monitoring and reporting of its source term. Any leads on Japanese media contacts who may be willing to report on the accident status or the lack of adequate radiological monitoring would be welcomed.

Another unaddressed issue: we have printed and distributed a number of op-eds and comments on the liability of the General Electric corporation and their obligation to provide some compensation to impacted Japanese communities and families due to the glaring design flaws at the Fukushima Daiichi reactors. These design flaws have received wide media attention in the United States (but not in Japan?) No US or Japanese media reporters have made the connection between the subprime reactor designs and the obligation of General Electric to establish a victim's compensation fund similar to that established by BP after the Deep Well Horizon debacle in the Gulf of Mexico. Comments on this issue are solicited.

A continuing controversy: why haven't Japanese, American, and European media reported on the increasing unavailability of information about the continuing real time radiological releases from all seven meltdown events? The technology to measure accident site emissions in becquerels/hr or becquerels per cubic meter of air contamination has been available for more than half a century and is utilized at all US reactors to measure airborne emissions from reactor operations. Atmospheric background radiation is typically 10 microbecquerels per cubic meter or less. Why is TEPCO reluctant to provide to the Japanese media timely information about the airborne emissions from each meltdown event?

A related question: isn't the systematic collation of accident release data a matter of A) honor, B) legal obligations, and C) a practical necessity given TEPCO's obligation to monitor and mitigate accident releases? What validity does their "roadmap to a closed-loop cooling system and a cold shutdown" have if the public does not have access to this data?

A final related question: will the information blackout in Japan about the ongoing accident emissions also characterize US media reporting in the event of a future meltdown in the US?

Thursday, July 21, 2011

Quote of the day

From the Wall Street Journal, July 19, 2011:

TOKYO—Local officials in Fukushima prefecture said on Monday that 411 more cattle potentially contaminated with radioactive cesium have been shipped around Japan, a development sure to fuel food-safety fears.

The prefectural government said the additional beef cattle found to have eaten contaminated rice straw came from seven farms in six municipalities in the prefecture, bringing the total number of potentially contaminated cattle shipped from Fukushima for
consumption to 554. Some of Japan's biggest supermarket chains have sold beef from the cattle.

The local government added that the rice straw had tested at up to 690,000 becquerels per kilogram, more than 500 times the
government's safety limit...

It still isn't clear whether contaminated feed necessarily contaminates beef from the cattle that eat it...

Japanese authorities already said Sunday that they intend to ban cattle shipments from Fukushima prefecture, and possibly wider areas, as more animals have been identified as having consumed feed contaminated with radioactive cesium released from the nuclear power plant.

Besides Fukushima, radioactive cesium-contaminated rice straw has been found in Miyagi prefecture, north of Fukushima, and Niigata prefecture, at farms supplied with Miyagi-produced straw.

The assertion that it isn't clear whether contaminated feed necessarily contaminates the beef from the cattle that eat it echoes the widespread belief that cataclysmic climate change has nothing to do with human activities. The discovery of 690,000 Bq/kg of Cs-137 in rice straw, the peak value in approx. 50 samples, illustrates the unavoidable reality that Fukushima Daiichi-derived radioactive fallout is in the same order of magnitude as that generated by the Chernobyl accident. The Wall Street Journal article provides no information about the testing locations in the Fukushima prefecture where contaminated rice straw has been monitored. The ongoing controversy of contaminated beef highlights the necessity of much more comprehensive monitoring of pathways to human consumption of Fukushima Daiichi-derived contamination, especially of the indicator nuclides I-131, Cs-134, and Cs-137.

TEPCO and NISA monitoring data, available at, provide ongoing measurement of soil contamination around the Fukushima Daiichi nuclear power station as measured in Bq/kg of soil. Air contamination is measured in microsieverts/hour and indicator nuclides in seawater as measured in Bq/cubic centimeter.

On July 4th, TEPCO reported radiocesium in wet soil on a reactor facility playground at 440,000 Bq/kg, again reflecting Chernobyl order of magnitude deposition levels. The highest air contamination levels on the reactor site are reported near the main building with dose rates on July 21st running between 315 to 333 microsieverts per hour. Other onsite locations reporting radiation dose rates of 30 to 33 microsieverts per hour at the main gate and 12 to 13 microsieverts per hour at the west gate. In contrast, normal background radiation dose rates are 0.27 to 0.7 microsieverts per hour. The radiation dose rate at the main building is about 1/7th of the peak value reported near the administration building on March 21, 2011 of 2,015 microsieverts per hour. TEPCO data, therefore, indicates significant radiation releases from all 7 accident sites are continuing with little or no variation in dose rates. The data reported by TEPCO and NISA graphically illustrate what is not being reported:

  • An ongoing release profile of the emissions from each fuel meltdown site as measured in Bq/hour. This provides much more accurate information about the status of these ongoing releases than ambient radiation dose rates.

  • A correlated emissions release profile consistently lacking in TEPCO monitoring is the measurement of airborne plume activity as expressed in Bq/cubic meter. Typical baseline airborne contamination levels range from 0 to 10 microbequerels per cubic meter. TEPCO reports airborne activity in locations well away from the seven point sources in Bq/cubic centimeter (a reporting unit 1 millionth of a Bequerel per cubic meter). The use of this much smaller reporting unit is a tip off of a major nuclear accident in progress.

  • TEPCO airborne dust nuclide analyses for radiocesium reports radiocesium contamination slightly above 1.0E-05 Bq per cubic centimeter in late May rising slightly in early June before falling in mid-June and rising again in late June. According to the data provided by TEPCO there didn't appear to be any significant drop off of Cs-137 contamination levels in airborne dust before early July, when data is no longer available. The TEPCO data can also be restated as measured in microbequerels per cubic meter, i.e. slightly above 10 microbequerels per cubic meter. This is only slightly above background levels. If this is uniformly the case, why are background radiation dose rates running so high near the main building, and what are the actual background radiation dose rates and emission levels at and above the seven meltdown sites? Obviously more information is needed.

  • Among the most notable deficiencies in TEPCO and NISA monitoring reports are the lack of a comprehensive radiometric survey of Cs-137 deposition levels in all prefectures in Japan. This information would shed much more light on the likely extent of contamination in cattle feed throughout Japan.

Thursday, July 14, 2011

Deception on the public broadcasting network

On July 13th, the National Public Broadcast program "It's Your World" replayed a June 14th program entitled "Powering America: Does Nuclear have a Future?" featuring Thomas Isaacs, Per F. Peterson, and V. John White. While the program made a number of interesting points pertaining to the future of nuclear power, particularly with respect to the likelihood of the future construction of much safer reactors characterized by passive reactor design where no water injection is needed to maintain cooling, the program was particularly unnerving in its failure to address two major controversies pertaining to the accident in Japan. These controversies are highlighted in our publication Fukushima Daiichi: Nuclear Information Handbook as well as in our publication announcement packet.

The design flaws in General Electric's boiling water reactors that played a major role in the Japan accident should be a major concern for all American citizens living downwind from America's 35 boiling water reactors. The accident in Japan graphically illustrates the vulnerability of aging nuclear reactors to meltdown accidents due to a combination of normal equipment deterioration such as steam tube deformation and sludge deposits in fuel assemblies and the startling design flaws illustrated by the Japan disaster. No mention was made of these issues in the broadcast.

Even more disconcerting was the failure to address the ongoing controversy pertaining to the lack of real time monitoring of the emissions that continue to characterize the accident in Japan. The technology to monitor these emissions as measured in becquerels per hour or becquerels per cubic meter has been available for almost a half century. The program focused on the lack of public trust for nuclear power in the future and inadvertently made a major statement fostering such mistrust by failing to discuss the need for a comprehensive survey of the source term releases of the Japan accident. Currently a comprehensive ground deposit survey is entirely lacking as are accurate weekly reports about contamination in the Japanese food supply. The hope for accurate monitoring symbolized by NISA's initial comprehensive reporting of ambient radiation levels as expressed in microsieverts per hour has since been compromised by a gradual reduction in reporting of monitoring data that would allow a reasonable evaluation of the status of an accident that may continue indefinitely.

Pers Peterson did mention the ongoing problem of the generation of large quantities of radioactive water, but otherwise avoided terminology such as nuclear accident, nuclear meltdown, and, especially, multiple interlocking meltdown event (MIME). The main question raised by this program is: in the case of a future meltdown event and quick release accident at a US boiling water reactor, will the reactor licensee, as well as the NRC, also withhold accurate information about the total amount of radioactivity released during the accident scenario? One would never know from listening to this deceptive program that the amount of radiation released from the Fukushima Daiichi accidents (7) is significantly larger than that released from Chernobyl.

Saturday, July 9, 2011

Kirkus Review of Fukushima Daiichi Nuclear Information Handbook

A review of the Pennywheel Press publication, "Fukushima Daiichi Nuclear Information Handbook" may be found here.

Thursday, June 16, 2011

Continuing and emerging issues pertaining to the accident at Fukushima Daiichi

Up-to-date radiological surveillance information about accident radiation releases is becoming more difficult to obtain. Individuals willing and able to assist us with compiling information about the following issues, please contact

  • Real time data about radiation releases from all seven accident locations (3 reactor vessels and 4 spent fuel pools) expressed in becquerels per hour has never been made available to the general public. While extremely high ambient radiation levels expressed in microsieverts per hour characterize the early stages of the accident (the first ten days) and have been available online, accurate information about the hourly release rates as measured in becquerels per hour and/or becquerels per cubic meter air contamination have not been made public. The technology for taking these measurements has been available for over 50 years. Important ongoing lingering questions include:

  • Why is a day-to-day summary of total gaseous, steam, and particulate emissions of the second stage of this accident not available now that manual cooling efforts have partially controlled the fission chain reaction that define criticality?

  • Why is the media not asking why this information has not been released?

  • Is there any possibility that the United States government will make public its now classified satellite-derived aerial radiological surveillance data pertaining to hourly gross gamma/beta emissions?

The accumulation of radioactive water from manual cooling efforts is also a source of accident radiation releases.

  • Why is there no publicly available information about the actual quantities of radioactive water produced by manual cooling efforts, their storage location and capacity, and the radioactivity of stored water as measured in becquerels per liter?

  • What is the daily water release rate excluding steam emissions?

  • Once the new water filtration system is set up by the French company, Areva, will the amount of cesium and other isotopes recovered from the radioactive water be available to the general public? (See below for water in-water out suggested synopsis.)

  • Why is there an information blackout about ground deposition of Cs-137 within the evacuation zone as well as within important agricultural areas within Japan?

  • Will TEPCO/NISA release accurate information about ground deposition of Cs-137 and other radioactive isotopes in all areas of Japan as measured in becquerels per square meter similar to that compiled by many countries after the Chernobyl accident? See the Nuclear Information Handbook for an extensive summary of Chernobyl fallout data.

  • To what extent are rainy season rainfall events and changing wind directions now spreading radiation in mainland Japan, especially in previously relatively un-impacted areas?

  • To what extent is remobilized ground deposition spreading radiation outside of the accident site and its immediate environs and what steps are being taken to avoid remobilization by human activities such as worker and equipment movement?

  • Why were surveillance reports of high levels of I-131 and Cs-137 deposited in "weeds" (see section I of the Nuclear Information Handbook) not accompanied by more extensive documentation of contamination levels in other agricultural products, including vegetables, milk, and tea?

  • Why are updated estimates of total accident emissions not available now that accident releases have been mitigated (but not ended) and the extent of fuel melting has been more fully evaluated?

Several other issues are emerging with respect to the Fukushima Daiichi accident.

  • Fuel cladding failure in aging US reactors has long been a safety concern. To what extent did fuel cladding failure, steam tube deformation, and accumulated sludge deposits impact the effectiveness of the post-earthquake emergency "scrams" (reactor shutdowns) at Fukushima Daiichi, when complete control rod insertion was essential for a rapid return to cold shutdown status? Was there any lingering criticality due to incomplete control rod insertion before the tsunami destroyed the backup generators that would have been a factor in the rapid evolution of the fuel meltdown events?

  • To what extent are ongoing fuel cladding failures at US reactors a threat to public safety, especially at vulnerable US boiling water reactors? See section IX of the Nuclear Information Handbook for a description of fuel assembly aging issues.

  • With respect to liability for the Fukushima Daiichi disaster, to what extent do the gross deficiencies in boiling water reactor designs, such as those at the Fukushima Daiichi complex, render the General Electric company liable for compensating the tens of thousands of Japanese residents who are permanently displaced? How does the 20 billion dollars paid by BP into a compensation fund following the Gulf oil spill compare to the obligations of GE for compensating Japan accident victims, which could conceivably be in the 20 to 100 billion dollar range?

  • Will the General Electric company set up an escrow fund to compensate future victims of a boiling water reactor accident in the United States, an increasingly likely possibility given the existence of 35 aging, subprime-GE-design boiling water reactors?

Water in - water filtered - water out synopsis

What is the water storage capacity of each reactor vessel and each spent fuel pool involved in the accidents at the Fukushima Daiichi complex?

  • What are the hourly and daily rates of the use of the water for manual cooling as measured in gallons for A) water sprayed onto the reactor vessels and spent fuel pools to cool them and B) water piped into the reactor vessels and spent fuel pools to cool them?

  • What is the total amount of water in reactor building basements, tunnels, and other areas?

  • What is the total amount of water in other storage areas such as barges, tanks, and trucks?

  • How many gallons of this water has been filtered to remove radiocesium and other source term contaminants?

  • What is the daily leak rate of radioactive water escaping into the ocean from these water storage areas, if any?

  • How does the total amount of water pumped or piped in for cooling purposes compare with the total amount of water within the reactor vessels, spent fuel pools, and all other radioactive water storage areas?

  • Will TEPCO make public the amount of the indicator isotope Cs-137 recovered by filtering the radioactive water at the accident site?

Thursday, March 17, 2011

Nuclear Disaster in Japan

Nuclear Disaster in Japan


This blog is sponsored by the Davistown Museum in Liberty, Maine, ( Department of Environmental History. This blog site has four missions pertaining to the recent publication of Fukushima Daiichi: Nuclear Information Handbook:

  • To provide an overview of the accident at the FD (Fukushima Daiichi) reactor facilities, with a concise introduction to reporting units, background radiation levels, exposure guidelines and pathways, contamination levels of concern, historic contamination baseline data, a comparison of the FD disaster with the Chernobyl disaster, and a summary of the inventory of fuel assemblies at FD.

  • To provide access to the most important and easy to interpret websites providing information about the radiological impact of the FD accident in Japan and in the U.S.

  • To promote the our recently published Nuclear Information Handbook.

  • To provide updates about the situation in Japan, including reports on ongoing radiological monitoring and/or the lack thereof.

The predecessor of the museum, the Center for Biological Monitoring (CBM) in Hulls Cove, Maine, was the sponsor of RADNET: Information about Source Points of Anthropogenic Radioactivity: A Freedom of Nuclear Information Resource. This pre-blog era website was active from the early days of the internet until 2000, when CBM was incorporated within the Environmental History Department of the newly incorporated Davistown Museum, a 501 (c) (3) organization. The contents of this blog, which includes comments and information pertaining to the Fukushima Daiichi disaster, are extracted from the online archives of RADNET and worldwide sources cited below. This material is published as a component of the museum's Nuclear Information Handbook (Special Publication 62). This handbook is available on in paperback and Kindle formats and is the 22nd publication issued by the Pennywheel Press and its editor, H. G. Brack. This blog is a working draft of the first section of this Handbook and may be updated even as the first edition goes to press. Revised editions of the Handbook will be printed as additional information becomes available about the accident at the Fukushima Daiichi facility, or at any other location where a nuclear accident of global significance ocurrs in the future. Editorial comments and additional information are always welcomed. Please contact As a 501 (c) (3) organization, the Davistown Museum welcomes donations to support the compilation of this blog and publication of the Nuclear Information Handbook.

This Nuclear Disaster in Japan blog, the RADNET archives, and the Nuclear Information Handbook, provide no information on the health physics impact of any nuclear accident or source point of anthropogenic radioactivity. Other than the Wikipedia sievert synopsis reprinted below, the mission of this blog and the Nuclear Information Handbook is to provide nuclide-specific data on radioactive contamination in abiotic and biotic environments documented in the reporting units described below. The FDA contamination guidelines, generic exposure guidelines, and RADNETs terrestrial contamination levels of concern provide essential information allowing the general public to evaluate the significance of data being reported in Japan, US, and elsewhere.

It is important to note that most human exposure to ambient radiation is expressed in sieverts. This is the starting point for estimating the severity of an accident and its immediate impact on humans, but the key data for evaluating any accident is the ground deposition of the indicator isotopes radiocesium (cesium-137 or Cs-137) and radioiodine (Iodine-131 or I-131), followed by the documentation of their uptake in the biogeochemical cycles of the food webs that result in exposure to humans, as expressed in the reporting units below. Other volatile accident indicator isotopes are Cs-134 and I-133.

Fukushima Daiichi Accident Status (March 31, 2011)

Enough information has now become available to indicate seven nuclear accidents are now in progress at the Fukushima Daiichi reactor complex. All involve the resumption of fission chain reactions after the loss of coolant that occurred due to the tsunami. The first indications of major problems at the reactor complex were the three hydrogen gas explosions that resulted from the continued generation of heat in the reactor vessels units 1 - 3. When these explosions occurred, which were graphically displayed on television, large releases of volatile fission products occurred (Cs-134, Cs-137, I-131, I-133). While full criticality has not yet occurred in any of the seven units, an intense well publicized effort by the Tokyo Electric Power Company (TEPCO) to cool the reactor facilities and prevent further melting of the reactor internals as well as further melting of the fuel assemblies is ongoing. If cooling is successful in preventing further intensification of fission chain reactions in the fuel vessels or additional melting of the fuel assemblies in the spent fuel pool, there may not be significant increase in airborne contamination beyond what has already occurred. The continued manual cooling of the reactor vessels and spent fuel pools by the use of firefighting equipment - an extremely primitive way to control seven ongoing nuclear accidents - is resulting in huge discharges of highly radioactive water into marine pathways. This is an unexpected scenario that did not typify the Chernobyl accident; the last big nuclear accident involving discharges to the marine environment occurred at Sellafield in England. At Fukushima Daiichi, the best case scenario probably involves a struggle to cool the reactor vessels and spent fuel pools that may continue indefinitely - possibly three to five years (The New York Times March 30, 2011). It is now obvious that significant quantities of fission products have already been released, as demonstrated by information provided to The Wall Street Journal that radioiodine has been documented in spinach collected 60 miles southwest of the plant on Friday, March 25th measuring 54,000 Bq/kg. The New York Times reports peak values of Cs-137 have reached 3.7 million Bq/m2 at a location 25 miles from the crippled reactor complex. The Times notes the standard used to remove populations from the Chernobyl site was 1.48 million Bq/m2; maximum contamination levels reached in areas as much as a thousand kilometers away from the Chernobyl site were 5.5 million Bq/m2 (see the Chernobyl Fallout Data section of this blog). It is now evident that a major nuclear accident is underway at the Fukushima Daiichi complex with the potential to surpass the source term (release totals) of the Chernobyl accident. The most ominous aspect of this ongoing disaster, other than the danger to the Japanese population, is its potential to contaminate food production in locations directly downwind from the accident site. The San Joaquin Valley in California, a major source of fresh vegetables for the United States and world grocery stores, is particularly at risk and has already received low levels of fallout. All other agricultural production areas in the U.S. are also potentially at risk. Isotope-specific data in the reporting units listed later in this blog will be essential for concerned citizens to evaluate the possible significance of contaminated agricultural areas and food and milk production. Rhetorical descriptions of the contamination such as "teeny weenie" (CNN) or "reassuring picture of very low risk" (Wall Street Journal) should not serve as a substitute for accurate scientific measurements of contamination reported in easy to understand conventional (e.g. becquerels) reporting units.

Nuclear Accident Synopsis Guidelines

The following guidelines and reporting units have been extracted from contemporary online information sources such as the International Atomic Energy Agency (IAEA), Centers for Disease Control (CDC), US Department of Energy, US Environmental Protection Agency (US EPA), US Food and Drug Administration (FDA), United States Department of Energy (US DOE), Scientific American, Greenpeace,, and the Center for Biological Monitoring RADNET archives.

Reporting Units for Radiation Exposure and Environmental Contamination

The principal reporting units now used throughout the world for the measurement of radioactivity in biotic and abiotic environments are “sievert” (dose), “becquerel” (activity), and “electron volt” (energy). One becquerel equals one disintegration per second of a radioactive substance. Each isotope has its own unique electron voltage (eV) or energy level. The activity and energy levels of each radioisotope and their decay modes (gamma, beta, or alpha) are the basis for any health physics impact dose assessment. The dosage of human exposure to external radiation is measured in micro- or millisieverts for ground shine, cloud shine, and deposits on shoes and clothes. Volumetric and surface contamination is measured in becquerels per kilogram, liter, or square meter. The power (energy) of each disintegration is reported in electron volts. Commonly encountered reporting units for human exposure to ionizing radiation and nuclear accident radionuclide concentration, deposition, and pathway movements are listed below. Relevant definitions follow this list.

Radiation Reporting Units
Ambient Radiation Exposure: Dose Reporting Units

· microsieverts per hour (μSv/hr)
· millisieverts per hour (mSv/hr)
· millisieverts per year (mSv/yr)
· nanograys per hour (nGy/hr)
· micrograys per hour (μGy/hr)
· aerial monitoring of ambient radiation: millirems per hour (mR/hr)
· 1 rem (R) = 0.01 sieverts (Sv)
· 1,000 millionths of a sievert (1,000 μSv) = 1 thousandth of a sievert (1 mSv)

Activity Reporting Units Expressed in Becquerels

· 1 curie = 37 billion becquerels = 37 GBq; to convert curies to becquerels, multiply by 37 billion
· air: microbecquerels per cubic meter (µBq/m3)
o airborne contamination may be in the form of dust, other particulates, or water vapor, including evaporated steam
o After the Fukushima Daiichi disaster, the Japanese government reported ambient air concentrations in “tens of thousands of terabecquerels per hour”; one terabecquerel equals one trillion becquerels.
o To convert becquerels per cubic meter to microbecquerels per cubic meter, multiply the Bq/m3 times 1 x 10-6
· aerial surveillance of gross beta/gamma ground contamination: (Bq/m2)
· surface contamination: becquerels per square meter (Bq/m2)
· surface contamination as measured in bequerels are also reported using prefixes:
o 1 MBq (M = mega = million) = 1,000,000 bequerels = 27 microcuries = 27 μCi
o 1 GBq (G = giga = billion) = 1,000,000,000 Bq = 27 millicuries = 27 mCi
o 37 GBq = 37,000,000,000 Bq = 1 Curie = 1 Ci
o 1 TBq (T = tera = trillion) = 1,000,000,000,000 becquerels = 27 Curies = 27 Ci
o 1 PBq (P = peta = quadrillion) = 1, 000,000,000,000,000 becquerels = 27,000 Curies = 27,000 Ci = 27 kCi
· milk and water: becquerels per liter (Bq/l)
o high contamination levels in water samples are sometimes reported in becquerels per cubic centimeter (Bq/cm3). A liter contains 1,000 cubic centimeters
· food: becquerels per kilogram (Bq/kg)

Other Activity Reporting Units

· The US has a tradition of reporting radioactivity in disintegrations per minute (d.p.m.) especially for low levels of radioactivity associated with weapons testing fallout
· To convert d.p.m. (disintegrations per minute) to becquerels, divide by 60 (e.g. 180 d.p.m. = 3 Bq)
· To convert becquerels to d.p.m., multiply by 60
· Older protection action guidelines use the reporting unit microcurie (μCi) to delineate intervention levels (1 μCi = 1,000,000 picocuries = 37,037 Bq) (United States Department of Health and Human Services 1982)
· Up until recently, the United States used the now antiquated reporting system of picocuries; 1 Bq = 27 picocuries
o To convert picocuries to becquerels, divide by 27 (27.027)
o To convert becquerels to picocuries, multiply the number of becquerels by 27 (27.027)
o To convert picocuries per cubic meter to becquerels per cubic meter, multiply pCi/m3 times 0.037

Energy Reporting Units

· 1,000,000 electron volts (eV) = 1 MeV (1 mega-electron volt)
· 1,000 electron volts (eV) = 1 meV (1 milli-electron volt)

f = quadrillionths = femto = 10-15

P = quadrillion = peta = 1015

p = trillionths = pico = 10-12

T = trillion = tera = 1012

n = billionths = nano = 10-9

G = billion = giga = 109

μ = millionths = micro = 10-6

M = million = mega = 106

m = thousandths = milli = 10-3

k = thousands = kilo = 103

Sievert (Sv)

  • An international unit of radiation dosage, which measures the amount of radiation that is absorbed by a person, usually expressed in microsieverts or millesierverts. One sievert is equal to 100 REMs, a dosage unit of X-ray and gamma ray exposure.
Becquerel (Bq)

  • One disintegration per second of a radioactive material, also defined as "The activity of a quantity of a radioactive material in which one nucleus decays per second."

Exposure Pathways

There are four basic pathways of human exposure to radiation resulting from nuclear accidents of any kind:

  • External: Accident location radiation shine, plume cloud shine, ground shine, shine from contaminated clothing and shoes

  • Absorption by dermal deposition

  • Inhalation: Plume inhalation and re-suspended ground deposition

  • Ingestion: Primary (from foliar and surface contamination), Secondary (via direct pathways to human consumption such as the forage-cow-milk pathway), and Tertiary (via indirect pathways to human consumption, e.g. the incorporation of contaminated whole foods such as milk, whey, wheat, corn, or soy into processed foods and their redistribution to markets in areas unaffected by ground deposition)
The first risks of exposure to a passing plume are:
  • Inhalation of biologically significant radioisotopes, including radioiodine, plutonium, cesium, and strontium particles

  • External exposure to cloud and ground shine

  • Exposure to contaminated surface water and contaminated surfaces will continue long after plume passage

  • After airborne plume particles have been deposited or have dissipated, ambient air and skin surface measurements provide almost no information about exposure.

  • Immediate exposure to contaminated air, or the contamination that might be on clothing or exposed skin, as measured in microsieverts, does not provide information about total exposure via absorption, inhalation, and ingestion.

  • The key question is, in fact, what is the “long term exposure” of an individual to contaminated food products via ingestion? The inhalation and absorption pathway or the ingestion of contaminated drinking water may be the most important exposure routes for individuals living near the accident site, including residents of Tokyo, during southern and southwesterly wind flows, but the ingestion pathway provides most of the exposure to individuals not living near the reactor site. Transfer of radioactive contamination into the food chain, especially in vegetables, wheat, soy, corn, milk, meat, and high fructose corn syrup, can provide exposure to individuals and communities that have experienced no radioactive fallout whatsoever from the Fukushima Daiichi accident.
MOX Fuel Pathway Alert

MOX fuel derived plutonium, curium and Americium isotopes will characterize reactor 3 emissions. Pathways of importance are inhalation of plume cloud particles and inhalation of resuspended particulates after deposition by rainfall events. If criticality in the Fukushima Daiichi reactor 3 reaches full meltdown status, contamination patterns will be hemispheric in distribution.

Deposition Mechanisms

In any nuclear accident, the radioactive plume results in two types of deposition: dry deposition and wet deposition. Atmospheric nuclear weapons testing resulted in the radioactive contamination of the stratosphere that involved relatively uniform hemispheric fallout from both wet and dry deposition. Chernobyl and the ongoing accident at the Fukushima Daiichi facility involved tropospheric contamination; the highest levels of ground deposition are associated with rain and snowfall events (wet deposition) and are erratically distributed by wind direction and rain/snowfall intensity.

Background Radiation

Total background radiation exposure averaged over large population groups (i.e. the entire population of the United States) is reported as 6.2 mSv/yr. This hypothetical exposure level assumes no person is being exposed to the plumes of any ongoing nuclear accident. "Background radiation" can be divided into two components.
  • Exposure to naturally occurring radiation, such as radon gas, cosmic radiation, and the ubiquitous naturally occurring radioactive substance potassium (K). (See the notorious banana equivalent dose noted below.) Approximately half of background radiation is from naturally occurring sources.

  • Exposure to routine anthropogenic sources such as radiological imaging (mammograms, CT scans, dental x-rays, radiation therapy, and nuclear medicine facilities.) Gackground radiation also includes exposure to the cumulative fallout from past nuclear weapons tests, residual accumulations of Charnobyl contamination, other nuclear power and fuel reprocessing accidents, the ongoing operation of nuclear power plants, and fossil fuel burning, especially coal.

The estimated exposures from background radiation noted below represent the average exposure of hundreds of millions of people. In reality, such "background exposure" varies widely with geographical location, exposure to sunlight via sunbathing, and use of medical technologies such at CAT scans (see below).

Annual exposure from all sources of background radiation (naturally occurring and anthropogenic) typically averages:

  • 0.0062 sieverts per year (Sv/yr)

  • 6.2 millisieverts per year (mSv/yr)

  • 620 millirems per year (mR/yr)

  • 6200 microsieverts per year (uSv/yr)
This level of exposure translates to
  • 1.7 millirems per day (mR/day)

  • 17 microsieverts per day (uSv/day)

  • 0.017 millisieverts per day (mSv/day)

  • 0.7 microsieverts per hour (uSv/hr)

  • 0.07 millirems per hour (mR/hr)

It should be noted that exposure can vary widely from time to time and from place to place, depending on wind and other environmental factors and source point activity.

EPA Action Levels

The level of exposure that the EPA considers actionable is 1000 mR, or 1 R, over four days. Measurements of radiation at these levels would trigger actions contained in the Protective Action Guidelines for Nuclear Incidents ( published in 1992. 1000 mR over four days can be broken down into the following daily and hourly exposure levels that should be a concern to all citizens and can easily be compared to the "background" radiation levels noted above.
  • 250 millirems per day (mR per day)

  • 0.0025 sieverts per day (Sv/day)

  • 2.5 millisieverts per day (mSv/day)

  • 2,500 microsieverts per day (uSv/day)

  • 10.415 millirems per hour (mR/hr)

  • 0.10415 millisieverts per hour (mSv/hr)

  • 104.15 microsieverts per hour (uSv/hr)

Individuals experiencing radiation exposure near or above these EPA action levels should immediately take precautionary measures such as sheltering, avoiding rainfall exposure, and avoiding intake of leafy vegetables. Washout Pathway to the Marine Environment High volume manual water cooling efforts at the seven Fukishima locations that experienced meltdown events have and will continue to result in the washout of large volumes of fuel-derived assembly inventories of fission products, including iodine 131 and cesium 137. The destination of the majority of washout effluents is the marine environment. Radioactive contamination is rapidly deposited in marine sediments. The United Nations publication on radiation sources (UN SCEAR......) provides a comprehensive overview of concentration ratios of anthropogenic radioactivity in the marine environment. (See below.)

Exposure Guidelines

  • The famous banana equivalent dose (BED) is derived from the fact that bananas contain the ubiquitous naturally-occurring radioactive isotope potassium (K): (1/2T = 1 billion years). Of all the potassium in the world, 0.0117% consists of this nearly harmless naturally occurring radioisotope. One gram of potassium has an activity level of 30 Bq. The relative insignificance of radioactive potassium in bananas should not be used to divert attention from the presence of biologically significant quantities of isotopes such as radioiodine or plutonium: 15 Bq of iodine-131 is a biologically significant activity level; 2.5 Bq/kg of plutonium-239 in any food mandates extreme precautionary measures. (

  • Average hourly radiation exposure: 2.8 microsieverts

  • Background radiation exposure: 3 millisieverts/year (varies widely with geographical location and may be as much as 20 times higher in sections of India, Iran, and Europe)

  • Total average radiation dose from all sources received by a person living in the U.S.: 6.2 millisieverts/year

  • Mammogram: 3 millisieverts

  • Chest CT scan (computed tomography or CAT scan): 6 to 18 millisieverts

  • Limit of exposure for nuclear workers for one year: 50 millisieverts (mSv)

  • Emergency workers at the Fukushima Daiichi site: 250 millisieverts (mSv)

  • Peak radiation dose at the boundary of the Fukushima Daiichi nuclear power station on March 16, 2011: 400 mSv per hour

1997 Revised FDA Radioactive Contamination Guideline

United States Food and Drug Administration. (March 5, 1997). Draft: Accidental radioactive contamination of human food and animal feeds: Recommendations for state and local agencies. Center for Devices and Radiological Health, U.S. FDA, Washington, D.C.

  • This draft was issued on 3/5/97, but not received as requested for review by RADNET until August 9, 1997. This proposed draft represents a radical revision of the 1982 FDA recommendations, which are rescinded by these proposed standards.

    • Derived intervention levels are far stricter (more conservative) than the 1982 regulations. Derived intervention levels for the radiocesium group (1,160 Bq/kg for 15 year old = 31,320 picocuries/kg) are far closer to the "levels of concern" which resulted in seizure of food containing 10,000 picocuries/kg of radiocesium following the Chernobyl accident.

    • The most radical change in these guidelines is the inclusion of numerous additional radionuclides for consideration following a nuclear reactor or other type of nuclear accident. (See Appendix E). The derived intervention level for transuranic nuclides such as 238Pu, 239Pu and 241Am range from 2.0 to 2.5 Bq/kg for a 3 month old infant. These more inclusive guidelines are an acknowledgment of the lessons of the Chernobyl accident, i.e. a major nuclear accident includes many different radionuclides whose health physics impact can not be delineated by a single protection action guideline standard such as 10,000 picocuries (370 Bq).

    • The one significant unfortunate lapse in this draft is the use of the "number of samples contaminated above regulatory limits" to summarize contamination levels derived from the Chernobyl accident without reference to the specific levels of contamination in the samples analyzed. (See tables C-1, C-2, and C-3). This continues the FDA inclination to withhold nuclide-specific data after incidents of widespread contamination of foodstuffs. The substitution of an arbitrary action limit to replace nuclide-specific data illustrates that the FDA is still inclined to withhold information about rising levels of radioactive contamination in the food chain. In the event of another accident, the use of this arbitrary limit raises the question: will the FDA withhold data if contamination trends up towards the derived intervention level? All levels of contamination below the DIL are, after all, "below regulatory limits."

  • "Recommendations on accidental radioactive contamination of human food and animal feeds were issued in 1982 by the Food and Drug Administration (FDA) (FDA 1982, Shleien et al 1982). Since then, there have been enough significant advancements related to emergency planning to warrant updating the recommendations." (pg. 1).

  • "DILs [Derived Intervention Levels] are limits on the concentrations permitted in human food distributed in commerce. ... Comparable limits were not provided in the 1982 FDA recommendations. DILs apply during the first year after an accident." (pg. 3).

  • "The 1982 FDA recommendations were developed from the prevailing scientific understanding of the relative risks associated with radiation as described in the 1960 and 1961 reports of the Federal Radiation Council (FRC 1960, 1961). Since 1982, FDA and the other federal agencies in the United States have adopted the methodology and terminology for expressing radiation doses provided by the International Commission on Radiological Protection (ICRP) in 1977 (ICRP 1977, ICRP 1984a, EPA 1987)." (pg. 5).

  • "The equation given below is the basic formula for computing DILs.

      • intervention level of dose (Sv)
        DIL (Bq/kg) =

        f x Food Intake (kg) x DC (Sv/Bq)
      Where: DC = Dose coefficient; the radiation dose received per unit of activity ingested (Sv/Bq). f = Fraction of the food intake assumed to be contaminated. Food Intake = Quantity of food consumed in an appropriate period of time (kg)." (pg. 8).

  • "The food monitoring results from FDA and others following the Chernobyl accident support the conclusion that I-131, Cs-134 and Cs-137 are the principal radionuclides that contribute to radiation dose by ingestion following a nuclear reactor accident, but that Ru-103 and Ru-106 also should be included (see Appendix C)." (pg. 10). ... "DIL is equivalent to, and replaces the previous FDA term Level of Concern (LOC)." (pg. 12).

  • "The types of accidents and the principal radionuclides for which the DILs were developed are:
    • nuclear reactors (I-131; Cs-134 + Cs-137; Ru-103 + Ru-106),

    • nuclear fuel reprocessing plants (Sr-90; Cs-137; Pu-239 + Am-241),

    • nuclear waste storage facilities (Sr-90; Cs-137; Pu-239 + Am-241),

    • nuclear weapons (i.e., dispersal of nuclear material without nuclear detonation) (Pu-239), and

    • radioisotope thermoelectric generators (RTGs) and radioisotope heater units (RHUs) used in space vehicles (Pu-238)." (pg. 13).

  • "For each radionuclide, DILs were calculated for six age groups using Protective Action Guides, dose coefficients, and dietary intakes relevant to each radionuclide and age group. The age groups included 3 months, 1 year, 5 years, 10 years, 15 years and adult (>17 years). The dose coefficients used were from ICRP Publication 56 (ICRP 1989)."

Health Physics Levels of Impact

  • 0 - 0.25 Sv (0 - 250 mSv): None

  • 0.25 - 1 Sv (250 - 1000 mSv): Some people feel nausea and loss of appetite; bone marrow, lymph nodes, and spleen damaged

  • 1 - 3 Sv (1000 - 3000 mSv): Mild to severe nausea, loss of appetite, infection; more severve bone marrow, lymph node, and spleen damage; recovery probable, not assured

  • 3 - 6 Sv (3000 - 6000 mSv): Severe nausea, loss of appetite; hemorrhaging, infection, diarrhea, peeling of skin, and sterility; death if untreated

  • 6 - 10 Sv (6000 - 10,000 mSv): Above symptoms plus central nervous system impairment; death expected

  • Above 10 Sv (10,000 mSv): Incapacitation and death
Terrestrial Contamination Levels of Concern

  • 3.7 Bq/m2: Begin monitoring of ambient exposure radiation levels (microsieverts per hour), terrestrial contamination levels above background (Cs-137, Bq/m2), and rainwater (I-131, Bq/l) via the EPA, CDC, DOE, FDA, IAEA, state, and local websites.

  • 37 Bq/m2: Expand monitoring to include measurements of local contamination of food, water, and milk by indicator nuclides I-131 and Cs-137 as measured in Bq/kg or Bq/l. Begin protective actions: avoid exposure to rainfall events, remove shoes and clothing before entering domestic environments, and shower after exposure to rain.

  • 370 Bq/m2: Expand protective actions: stay indoors whenever possible, close windows, seal openings, cover gardens with tarps, shelter livestock, avoid ingestion of leafy vegetables and fruits harvested in fallout areas. Expand monitoring of food, water, and milk; discard or avoid ingesting foods and water contaminated by the indicator nuclides I-131 and Cs-137 above 370 Bq/kg or Bq/l (10,000 picocuries, the protection action level used by the US FDA to dispose of imported foods contaminated by Chernobyl-derived fallout). Continue monitoring of ambient radiation levels.

  • 3,700 Bq/m2: Expand protective actions to restrict movement of children, outside workers, nonessential travel, and recreational activities such as hiking and sunbathing. Closely monitor food, milk, and water intake, sources, and radiation levels. Continue use of information technology to keep informed of ongoing emissions. Immediate sheltering is the best option to avoid exposure to a passing plume.

  • 37,000 Bq/m2: Prepare to evacuate to a safer zone, e.g. the southern hemisphere or another planet.
Without the systematic compilation of the distribution pattern of the indicator radioisotopes I-131 (1/2T = 8 days) and Cs-137 (1/2T = 30 years), no reasonable evaluation of the health physics impact of the Fukushima Daiichi disaster or any other nuclear accident or point source can be tabulated. Historic Baseline Contamination Levels

Nuclear weapons fallout levels

  • Denmark: maximum fallout deposition occurred in 1963: 988 Bq/m2 Cs-137 (RISO National Lab)

  • US: maximum fallout deposition occurred in 1963: +/-2,500 Bq/m2 Cs-137 (downwind) Weapons testing location depositions were much higher but deposition levels are classified information.
Chernobyl-derived fallout levels
  • Denmark: Denmark was considered an "unaffected" area; maximum deposition was 1,210 Bq/m2 Cs-137 in 1986

  • Northern England, Sweden, Finland: +/-100,000 Bq/m2 Cs-137 (1986)

  • Areas of maximum fallout in Russia: +/-1,000,000 Bq/m2 Cs-137

Chernobyl vs. Fukushima Daiichi: Accident Overview

The ultimate size and impact of the unfolding accident at the Fukushima Daiichi plant in Japan is unknown. With good luck and effective countermeasures, the source term releases at Fukushima Daiichi could be one or two orders of magnitude less than the source term releases from Chernobyl. Unfortunately, given the complexity of the Daiichi reactor complex, which includes three at-risk reactor vessels and four at-risk spent fuel pools, the worst case scenario could involve source term releases one order of magnitude above that of the Chernobyl accident. The New York Times had an excellent summary of the number of fuel assemblies in the reactor vessels and spent fuel pools at the Japan facility in its Friday, March 18th edition. A summary of this information follows this overview. It could take weeks, months, or even years before the Japanese and U.S. governments and the IAEA (International Atomic Energy Agency) will be able to provide even the most preliminary estimates of release inventories.
The extraordinary situation in Japan involves not one, but four, nuclear reactor installations. The most important information about this accident-in-progress pertains to the huge quantities of radioactive fuel and waste involved. The Chernobyl accident involved a single reactor with an inventory of approximately 8 million curies of radiocesium, one of the most biologically significant isotopes in an accident plume, of which two million seven hundred thousand curies were discharged into the troposphere during the accident (Aarkrog, A. (1994). Source terms and inventories of anthropogenic radionuclides. Riso Nat'l. Lab., Roskilde, Denmark). In the ongoing accident at the Fukushima Daiichi, Japan facilities, +/- 40 million curies of radiocesium are at risk of being discharged into the environment in a worst case scenario. The accident is further complicated by the fact that at reactor number three, MOX fuel, which is partially composed of reprocessed plutonium and uranium oxides, has the potential to release large quantities of plutonium isotopes into the troposphere as the accident unfolds. An additional complicating factor, not yet being discussed in the media, is the fact that the Chernobyl accident effectively ended after nine days when the fuel, having melted through the bottom of the reactor structure, which had no containment, solidified and then stopped emitting large quantities of radiation. It is highly unlikely that this solidification process will occur at any of the four facilities now in the process of releasing radioactivity to the environment. It is important to note that a comprehensive description of the Chernobyl accident did not appear until A.R. Sich completed his MIT Ph.D thesis (1994) on the accident and began publishing articles in Nuclear Safety and Nuclear Engineering International (1994-96; see citations below). In the case of the ongoing disaster at the Fukushima Daiichi facility, it may also take a decade to fully document the source terms (total release inventory), patterns of dispersion, and causes of the accident. The current assertions that any releases from this accident will have a minimal environmental and health physics impact have no credibility and cannot be determined until all emissions from the Fukushima Daiichi complex and its spent fuel pool inventories have ended and systematic biomonitoring of all release pathways and contamination levels have been completed. The timeframe for these evaluations will be years. The following definitions are intended as an aid for the average person who is not a nuclear expert to understand the basic terminology and biological significance of the unfolding disaster at the Fukushima Daiichi facility. The fundamental question that all concerned world citizens have or will soon have is: how much radioactivity is my community and my family being exposed to?

The Problem of Exposure to Ambient Radiation

The fly in the ointment pertaining to any nuclear accident or nuclear discharge exposure scenario is the fact that the radiation detecting equipment that measures ambient air contamination, or the surface contamination of radioactivity on skin and clothing, provides only a fragment of the information needed to evaluate actual exposure. Accidents such as the ongoing disaster in Japan create plumes of radiation, which are then deposited on terrestrial landscapes by rainfall events. The accident at Fukushima Daiichi is also characterized by the discharge of large volumes of contaminated seawater as a result of the improvised attempts to cool the fuel assemblies. Buildup of sea salt residues within the reactor vessels and spent fuel pools will further complicate accident remediation activities.

Contamination derived from the Fukushima Daiichi plant and other accidents is then taken up by the biogeochemical cycles of the earth’s biosphere, exposing all living creatures, including humans, to anthropogenic (manmade) radiation, the levels of which can exceed exposure to naturally-occurring radiation The accident at the Fukushima Daiichi facility may well turn out to be a historically difficult-to-remediate labyrinth of long-term chronic contamination point sources.

Once an accident plume has passed, measurements of ambient radioactivity levels provide little or no information about exposure. The tragedy of the ongoing Japan disaster is that radioactivity will be emitted continuously for a long period of time; its terrestrial deposition will depend on accident duration, accident intensity, wind direction, and ocean current dispersal of liquid contaminants. Rhetorical commentary on the accident plume, such as “radioactivity is low” or “such and such location will have a minimum impact from this accident” should have zero credibility. The actual evaluation of the amount of radioisotopes in the environment must await laboratory analysis of the contaminant load in impacted abiotic and biotic media. In places such as California, Oregon, and Washington, which began receiving tiny amounts of radioactivity on Saturday (3/19/11), an evaluation of the significance of the radiological impact of the Fukushima Daiichi accident can only be measured by a laboratory analysis of the soil deposition of the indicator isotope radiocesium, as measured in becquerels per square meter. If new cesium deposits can be documented (on top of old weapons testing and Chernobyl radiocesium baseline deposits), new deposits of radioiodine-129 (1/2 T = 8 days), and other biologically significant isotopes, including MOX fuel-derived plutonium-239 (1/2 T ±24,000 years,) will also be present. The analytic techniques that measure gamma and beta emitting radiocesium will not apply to alpha emitting plutonium, which will require additional time consuming laboratory measurements.

Exposure to accident plumes cannot be evaluated until the following information is available:
  • How many becquerels per square meter of the accident indicator isotope cesium-137 have been deposited in my community?
  • How many becquerels per liter of cesium-137 are in the milk, including breast milk, that my children are drinking?

  • How many becquerels of I-131 are in public and private drinking water supplies that my family is utilizing?

  • How many becquerels of I-131 are in milk, including breast milk, that my children are drinking?
Fukushima Daichii Fuel Assemblies
On 3/18/2000, the New York Times printed the following summary of the number of fuel assemblies in the reactor vessels and spent fuel pools of the six reactors at the Fukushima Daiichi facility.

  • Reactor 1: 400 in reactor vessel and 292 in spent fuel pool

  • Reactor 2: 548 in reactor vessel and 587 in spent fuel pool

  • Reactor 3 with MOX fuel: 548 in reactor vessel and 514 in spent fuel pool

  • Reactor 4: 0 in reactor vessel and 1,479 in spent fuel pool

  • Reactor 5: 548 in reactor vessel and 826 in spent fuel pool

  • Reactor 6: 764 in reactor vessel and 1,136 in spent fuel pool

  • Common storage spent fuel pool: 6,291
The New York Times has indicated that the rods in the common storage pool "have cooled enough to pose little threat of igniting." The Times indicates the temperatures of the assemblies in the spent fuel pools in reactors 5 and 6, which were both shut down before the quake, have risen from 77 degrees F, the normal temperature, to 145 and 140 F. More recently, the Fukushima Daiichi reactor operators have indicated electricity and thus fuel pool cooling have been restored to these reactors, both of which were not operating at the time of the earthquake and tsunami. The main danger of a meltdown is in the reactor vessels of units 1 - 3 and the spent fuel pools of units 1 - 4, having a combined inventory of 4,368 assemblies. Each assembly contains approximately 10,000 curies of Cs-137, providing an approximate inventory of 43,680,000 curies in the assemblies most at risk. A worst case scenario release, as at Chernobyl, would probably involve no more than the release of 30% of this inventory, or 13,104,000 Ci. This compares with a source term release at Chernobyl of 2,700,000 million curies (Aarkrog 1994). The current situation at the Fukushima Daiichi facility is unknown; hopefully a worst case scenario accident involving meltdown of all four reactors will not occur.

Accurate Publicly Available Information?

Two key issues bedevil the accurate reporting of the extent of contamination from any nuclear accident and the health physics significance of accident emissions. The preceding series of definitions will hopefully mitigate the first issue: the confusing terminology of the many reporting units used by various governmental, corporate (e.g. TEPCO), and environmental organizations. The second issue is much more difficult to alleviate: the lack of knowledge of the reporters and commentators who provide news about the Fukushima Daiichi disaster and other accidents. A March 23, 3011 article in the Wall Street Journal graphically illustrates this conundrum. Carl Bialik reports Tokyo Electric Power Company's main gate gamma radiation level reading at 240 microsieverts per hour (uSv/hr), a fairly low reading considering that seven nuclear accidents are occurring all at once, and then reports spinach collected "60 miles southwest of the plant last Friday contained 54,000 becquerels of the radioactive element iodine-131." He continues, "All the numbers add up to a reassuring picture of the very low risks from the radiation emitted from Fukushima so far, which is less than the amount people typically get from common sources such as the sun, medical tests, and air travel." (Bailik 2011). Given the FDA derived intervention level of 167 Bq/kg for radioiodine-131 for a one year old child and the annual, daily, and hourly background exposures noted above, The Wall Street Journal report becomes a pardigm for the misinformation that will characterize most reporting on the ongoing Fukushima Daiichi accidents.

Fukushima Daiichi Radiological Surveillance Data
Visitors to the blog, please email us at: with additional suggestions about other sources of information on Fukushima releases and plume pathways.

Radiation Surveillance Data Sources

Japanese Information:

Dr. Ryugo Hayano of Tokyo University's Compiled Timelines -- Timelines of radiation data on Twitter, same data on Lockerz here:

Radiation Monitoring Map in Japan -- Shows individual monitoring points with the recent data in a line graph

Compilation of Information from the Japanese Government
-- WIDE project's compilation of links

SPEEDI -- System for Prediction of Environment Emergency Dose Information, shows disaster prevention data

Japan Open Radiation Dashboard -- Shows graphs of radiation data by prefecture

Realtime Map of SPEEDI -- Shows levels at each monitoring station, color coded

Spreadsheet of Current Reactor Conditions -- Shows actions being taken on each reactor

MEXT - Japan's ministry of Education, Culture, Sports, Science and Technology's readings by prefecture

Excerpts from Michiko Otsuki's blog (a TEPCO worker on the scene)

U.S. Information:

University of California, Berkeley Nuclear Engineering Dept. -- has data on radiation sampling in milk, rainfall, river water, and air in becquerels and equivalent dose

Where are the Clouds? -- A blog covering the movement and impact of the radioactive plume

US. Department of Energy -- Links to slideshows of graphical representations of aerial monitoring data over time

EPA's RadNet map
Another RadNet map interface

Black Cat Systems Online Geiger Counter Nuclear Radiation Detector Map -- Amateur network of Geiger counters -- another amateur Geiger counter network

Oregon State Department of Health Monitoring Data -- Updated daily

Texas A&M Plume Trajectory Projections

MIT Nuclear Information Hub

Reuter's Japan Earthquake Blog

Sources From Other Countries:

IRSN, Institut de Radioprotection edt de Surete Nucleaire (French)

NILU - Realtime mapping of radioactive releases's Radiation data Set Maps -- Shows various monitoring stations and the change in radiation levels over time

Any information or sources of similar data would be greatly appreciated!

Basic Definitions and Concepts

The following definitions are extracted from RADNET: Information about Source Points of Anthropogenic Radioactivity, the online archives of the Center for Biological Monitoring, now part of the Department of Environmental History of the Davistown Museum as well as from other online sources. Additional definitions and comments will be added to this section as the Fukushima Daiichi accident scenario unfolds. Corrections, comments, and new information are solicited. Additional information is available in the Davistown Museum’s Center for Biological Monitoring Archives (RADNET) about historically significant chronic point sources, many of which continue to exposure human communities to biologically significant quantities of anthropogenic radioactivity.

Of particular importance to those seeking more information about the Fukushima Daiichi disaster, an ongoing accident whose significance and extent cannot yet be evaluated, is RADNETs Chernobyl fallout data annotated bibliography, also posted on this blog. Chernobyl fallout patterns and intensity, as well as the RISO National Laboratories weapons testing fallout database, provide information essential to evaluating the impact of the Japan disaster. The Oak Ridge National Laboratory database for cumulative fuel waste inventories provides the basic information to estimate Cs-137 inventories in the fuel assemblies of aging nuclear reactors (+/- 10,000 Ci of Cs-137 per fuel assembly.) See below.

RADIOACTIVITY: The spontaneous decay of the nucleus of an atom by the emission of particles, usually accompanied by electromagnetic radiation. It is also defined as the mean number of nuclear transformations occurring in a given quantity of radioactive material per unit time, expressed in sieverts (Sv - human exposure), becquerels (Bq - quantitative measurement), or curies (Ci - activity levels). Most radionuclides (radioactive nuclides in contrast to stable nuclides) have multiple forms of radioactive emissions, and are classified according to their principal decay modes. The most common types of radiation are:

ALPHA RADIATION: e.g. emitted by plutonium-239: a nucleus of a helium atom; large in mass, unable to penetrate more than a few microns of biological tissue. (e.g. cannot penetrate a piece of paper)

BETA RADIATION: e.g. emitted by tritium: a high speed electron, small in mass, moderate penetrating abilities, e.g. unable to penetrate more than a few millimeters of biological tissue.

GAMMA RADIATION: e.g. emitted by zirconium-95: electromagnetic radiation; highly penetrating, very energetic x-rays emitted by an excited nucleus. Will often but not always exit living tissues without depositing its biologically significant electron voltage (ev).

CURIE: The fundamental measurement of radioactivity in the environment: the amount of radioactive material giving off 3.7 x 1010 d.p.s., or 37 billion disintegrations per second. One disintegration per second is called a becquerel and is now the universal reporting unit for radioactive contamination. In the United States, the picocurie (1 pCi = 0.037 d.p.s. or 1 x 10-12 of a curie) was once the unit used for many measurements of radioactive contamination, and may again appear as a reporting unit with respect to the unfolding catastrophe in Japan.

GRAY: The gray symbol (Gy) is the SI unit of absorbed radiation dose of ionizing radiation (for example, X-rays), and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter (usually human tissue). In other words, one Gray is the absorption of one joule of energy, in the form of ionizing radiation divided by one kilogram of matter.

RADIOACTIVE HALF-LIFE (1/2T): The time required for one half the atoms in a radioactive substance to decay. For example, the radioactive half-life of cesium is 30.174 years, 1/2T = 30.174 y. Radionuclides with short half-lives are hot, emitting large amounts of radiation but decaying quickly and contrast with radionuclides with longer half-lives whose energy is emitted over a longer period of time. The biological half-life is the time required for the body to eliminate 1/2 of a radioactive substance by regular physiological processes of elimination. This definition differs slightly from effective half-life which is the time required for 50% of the radioactive contamination to be diminished by both radioactive decay and biological elimination.


  • To convert picocuries to becquerels, divide by 27 (27.027).
  • To convert d.p.m. (disintegrations per minute) to becquerels, divide by 60.
  • To convert becquerels to picocuries, multiply the number of becquerels by 27 (27.027).
  • To convert picocuries per cubic meter to becquerels per cubic meter, multiply pCi/m3 times 0.037.
  • To convert becquerels per cubic meter to microbecquerels per cubic meter, multiply the Bq/m3 times 1 x 10-6.
These conversion factors are essential for interpreting baseline data contained in this website because all European environmental monitoring data are expressed in becquerels (per square meter for ground deposition, per cubic meter for air concentration, per kilogram/year for total dietary intake, etc.) See the Table of Prefixes.

ELECTROMAGNETIC RADIATION (E.M.R.): Energy radiated in the form of a wave which can accelerate charged particles. Electromagnetic radiation can travel through a vacuum. Its energy varies greatly; radio waves have the longest wavelengths and the lowest frequency and energy (1.2398 x 10-10 to 1.2398 x 10-5 electron volts. X-rays and gamma rays have the shortest wavelengths and highest frequencies and energies (up to and above 6 x 106 electron volts). For a comprehensive explanation of the public health consequences of ionizing radiation, i.e. electromagnetic radiation above 155 ev. See Section 10 in Gofman, J.W. 1981. Radiation and human health; a comprehensive investigation of the evidence relating low-level radiation to cancer and other diseases. Sierra Club Books, San Francisco.

FISSION: A process, which, along with fusion, releases energy stored in separated nuclei. During fission, a fissionable nucleus such as plutonium absorbs a neutron, becomes unstable and splits into two nuclei, releasing energy. Nuclear power is a controlled, self-sustaining fission process; nuclear explosions are an uncontained chain reaction version of the fission process. In the detonation of thermonuclear (fusion or hydrogen) bombs, the fission process is the trigger for the more powerful fusion event. Fission products are the artificial radioactive offspring of nuclear industries and accidents; their inventories and pathways in the environment are the subject of this website.

IONIZING RADIATION: Radiation with energy above 155 ev which has the ability to knock other electrons out of the orbits of atoms and molecules, often creating more ionizing radiation and adversely affecting living tissues. Biologically significant radiation is an ionizing dose of radiation above 155 ev which may have carcinogenic, mutagenic, or teratogenic health effects in humans.

DAUGHTER PRODUCTS: A synonym for decay products, resulting from the radioactive disintegration of a radionuclide. Daughter products can either be stable or radioactive. Many important radionuclides are components of other nuclides' decay series: e.g. niobium-95 is a decay product of zirconium-95; neptunium-237 is a decay product of americium-241; americium-241 is a decay product of plutonium 241. Plutonium-238, the third most common constituent in spent fuel, is a decay product of neptunium 238. All curium nuclides decay to plutonium isotopes. Also called "growing in." An important daughter product of ubiquitous gaseous stack releases of nuclear reactors is Cs-134, a daughter product of Xe-133.

EFFECTIVE ACTION LEVEL (FDA): Following the Chernobyl accident, the Food and Drug Administration implemented an unofficial protection action guideline when it observed high levels of Chernobyl-derived radiocesium contaminating imported foods approximately one year after the accident. The FDA seized and destroyed foods contaminated in excess of 10,000 pCi/kg (370 Bq/kg), thereby setting an EFFECTIVE ACTION LEVEL which was significantly more conservative (lower) than the protection action guidelines promulgated by various U.S. government agencies before and after the Chernobyl accident. See RAD 6 for a more complete description of the wide variety of protection action guidelines.

EXPOSURE PATHWAY: The route that links radioactive contamination from a specific source point to a receptor population in a specific ecosystem.

HOT PARTICLES: Air-borne particles of partly volatilized fuel from nuclear accidents or from defective fuel cladding which can also be carried by liquid effluents. Hot particles from leaking reactor fuel are also known as "fuel fleas" because they become electrically charged as a result of radioactive decay and "hop" from one surface to another. Typical hot particles are ~10 µm in size and can contain nuclides ranging from activation products to reactor derived fission products (e.g. 95Nb, 95Zr, 103,106Ru, 141,144Ce, etc.) which were widely dispersed after the Chernobyl accident. (For a bibliography of articles on Chernobyl derived hot particles, see RADNET Section 10.) CRUD is another type of hot particle.

INDICATOR NUCLIDES: The principle radioactive products of nuclear industries or accidents. In the first few days of a nuclear accident, radioiodine-131 dominates the activity release profile. Other longer-lived radionuclides such as 106Ru, 137Cs, 239Pu dominate the later time compartments of the release pulse, producing exposure long after media coverage of a nuclear accident has faded and radioiodine-131 levels have subsided (See plume pulse pathways, RADNET Section 7). Cesium-137 is the most significant of the many nuclides that remain after the short-lived radionuclides have decayed.

PEAK CONCENTRATION / MEAN CONCENTRATION: The peak concentration is the highest reading in a series of samples; the mean concentration is the average of readings in a series of samples.

Nuclear accidents and mishaps are commonplace events at nuclear reactors, weapons production facilities, and other nuclear installations - the Three Mile Island accident was not the "last" nuclear accident that occurred in the United States. The following is a quick synopsis of accident scenarios.
  • Reactor water system leaks: a very common form of mishap at many nuclear reactor facilities. The release of tritium to groundwater is a tip off of ongoing reactor water system leaks, and has been documented at dozens of US reactors. More serious water system leaks will also release fission products.

  • Fuel cladding failure accidents: A fuel cladding failure accident occurred at the Maine Yankee Atomic Power Company in the late 1990s and resulted in the closure of the plant. According to licensee records, 66 failed fuel assemblies released fuel pellets into the reactor water system. Some of these were removed by vacuums and placed in the spent fuel pool, but the majority of fission products remained in the reactor vessel as "low-level radioactive waste" and was buried with the reactor vessel in South Carolina when the facility was decommissioned in 1999. The most notorious fuel cladding failure accident occurred at the Haddam Neck, CT, reactor site and released large quantities of fission products to the atmosphere in the early 1990s.

  • Spent fuel pool loss of coolant accident (LOCA): Four LOCAs are now underway at the Fukushima Daiichi complex. Loss of spent fuel pool cooling results in fuel assembly overheating, followed by fuel pellet expansion, fuel assembly swelling, cracking, and deformation. Fuel assemblies may then burst open, releasing fuel pellets as well as fission products into the remaining coolant. A total loss of coolant can result in the gradual melting of the entire fuel pool fuel assembly matrix. The large quantity of fission products being washed out of the Fukushima Daiichi spent fuel pools and into basements, drains, and the marine environment are an indication that a loss of coolant accident is well underway in these units. The timeframe for the duration of an uncontrolled LOCA is unknown but could be measured in months and possibly even years.

  • Loss of reactor coolant accident (LORCA): The accident at Three Mile Island was a LORCA that was eventually resolved by the resumption of the cooling of the reactor vessel spent fuel assemblies. LORCAs appear to be underway at three of the six Fukushima Daiichi reactor units. The other three units were not critical, that is undergoing fission chain reactions, at the time the tsunami destroyed the backup cooling systems. A LORCA occurs when a reactor vessel is breached or otherwise damaged and fuel assembly coolant (usually water) is no longer available. The continuing fission chain reaction can intensify resulting in the melting of fuel followed by the melting of the reactor vessel internals, bursting of pipes, and damage to pressure operated relief valves. This is called a "serious core event" and can intensify as a function of time, coolant dispersal, and damage to the pressure vessel as the primary pressure boundary. Once the pressure vessel is breached, large releases of fission products will occur. Continued heating of the fuel assemblies can result in a total meltdown; the extreme heat generated by an ongoing meltdown will eventually result in the melting of the pressure vessel and the dispersal of the molten fuel into the ground or groundwater underneath the reactor vessel. This is the worst case scenario accident for an operating nuclear reactor other than vaporization.

  • Vaporization: Vaporization of a nuclear reactor complex, including both the spent fuel pool and the reactor vessel and its fuel assemblies can occur during a nuclear attack. During the Cold War, the United States and Russia both targeted each other's nuclear facilities. Vaporization of a nuclear reactor site or weapons production facility as a result of nuclear war or terrorist attack would result in the dispersal of the entire cumulative inventory of the facility or facilities. The world catastrophe that would follow would result from the efficient vaporization of all onsite fission products, with a release of 25 to 500 times the contamination discharged at the Chernobyl accident.

RADIOMETRIC SURVEY: A radiological survey of a contaminated site, especially sediments, soil, or other media containing sufficient data points to characterize the spread of contamination from a particular source point isometrically, i.e. via contour maps using isopleths which express the values of the data points. Aerial radiometric surveys have been utilized since the 1950's to characterize oil bearing geological formations, by the defense department for analyses of Russian and other weapons production facilities, and after the Chernobyl accident to characterize fallout in Russia, Sweden, and England. Radiometric surveys of fallout patterns from the Japanese disaster will be expressed in becquerels per square meter as soon as state and federal reporting agencies analyze soil samples for contamination. Such survey reports should begin with baseline data documenting weapons testing fallout and Chernobyl accident contamination residues, which existed at the beginning of this accident. Due to the size of the potential release from Japan (±40 million curies of the indicator nuclide radiocesium) and the probable long term emissions scenario (months, possibly years), surface contamination analysis should be done weekly, if not daily, in locations such as the states of California, Oregon, and Washington. Links to other environmental protection and monitoring websites providing information about the accident at Fukushima Daiichi will be posted on this website as they become available.

BIOLOGICALLY SIGNIFICANT RADIONUCLIDES: Radioactive substances such as plutonium, cesium, strontium, radioiodine, and tritium, etc. that provide the most significant health hazards to humans among all nuclides released from anthropogenic sources. Biological significance is a result of a combination of high decay energy, biogeochemical availability, efficient energy transfer to biological systems, and ubiquitous production during nuclear accidents and from industries. In this website, biologically significant radionuclides are noted as indicator nuclides and are used to characterize inventories and pathways of nuclear effluents in the biosphere. The biological significance of radiation results from the enormous amount of energy contained in each emission. Visible light has an energy range of 1.77 to 4.13 electron volts (ev). Most chemical changes occur within a range of 5 to 7 electron volts (ev). Biologically significant radiation levels range from 18,610 ev (0.01861 Mev) for the weak beta emitting tritium (1/2T = 12.346 yr.) to 511,630 ev (0.51163 Mev) for the ubiquitous cesium-137 (1/2T = 30.174 yr.) to 5,155,400 ev (5.1554 Mev) for the highly radiotoxic plutonium-239 (1/2T = 24,131 yr). These highly energetic emissions carry enough energy to tear electrons from neutral atoms and molecules. In delicate biological tissues, the impact of introducing radiation containing hundreds of thousands to millions of electron volts "can only be described as chemical and biological mayhem" (Gofman, 1981, p. 22). For example, the alpha radiation resulting from the decay of plutonium-239 has little penetrating power due to its large mass, but, if inhaled and deposited in the lung, is among the most radiotoxic of nuclides since its 5,155,000 ev (5.155 Mev) will be distributed within the area of only a few cells. The weaker beta radiation of tritium (3H) is slightly more penetrating than alpha radiation; its biological significance comes from its ubiquitous production during the fission process, its tendency to follow the water cycle in nature, and its ability to become tissue bound in humans and the biotic environment. Cesium-137, a beta emitter with a gamma component, is biologically significant due to its energy level, its long half-life, its ubiquitous production during the fission process, and its tendency to follow the potassium cycle in nature, giving a whole body dose to those who ingest it.

SOURCE TERM RELEASE: Radioactive waste inventories discharged from a particular nuclear accident or source point, e.g. Chernobyl, Sellafield, weapons tests, etc. Each plume is characterized by a unique fingerprint of radioactive emissions which can be identified by a particular series of isotopic ratios. Weapons testing fallout was high in radiostrontium, low in cesium-134, and, thus, differed from the Chernobyl source term which had much less radiostrontium and a higher ratio of cesium-134 to cesium-137 than weapons test fallout. Eisenbud (1987. Environmental radioactivity. Fourth edition. Academic Press, Orlando, FL) and most early reports on the Chernobyl accident, in a classic example of misinformation, based the source term for Chernobyl upon Russian data which only included inventories of radionuclides deposited on Russian soil. Further research indicated that the source term release for Chernobyl included larger quantities of radioactive emissions than initially estimated and much higher levels of contamination than expected in locations which were a great distance from Chernobyl. An important study of the pre-Chernobyl sources of radioactivity, including naturally occurring, industrial, atomic power, weapons testing, and fuel reprocessing sources is the UNSCEAR Text (1982) (See RADNET Section 14); important U.S. and Russian military source points are excluded. A more detailed summary of the impact of the Chernobyl accident is contained in Section 10 of this website.

SOURCE TERM RELEASE DURATION: The source term release duration can vary from a few seconds for a weapons test explosion to hundreds of years or more for chronic discharges from source points such as military weapons production facilities. In the case of the Japan disaster, the source term release duration, and thus ongoing contamination of the biosphere, has the potential to be measured in years.

CRITICAL MASS: The minimum mass of fissionable material which can achieve a nuclear chain reaction with a specified geometrical arrangement and material composition. (Center for Disease Control (CDC), Savannah River Site (SRS) dose reconstruction, 1999).

BIOINDICATORS: Biological media which are the most susceptible to the accumulation of biologically significant radionuclidi. Many bioindicators are in pathways to human consumption, allowing rapid transfer of radioactivity from the abiotic environment (air, precipitation, freshwater, sea water, soil and marine sediments) to sentinel organisms as well as crops and crop products such as milk, cheese and meat. Most pathway analyses for the ecological cycling of radionuclides begin with soil or sediment as the repository of radioactive contamination. The process by which living organisms absorb radioactive contamination is called bioaccumulation; bioaccumulation may also be defined as the assimilation of contamination prior to its movement up the food chain. Among the most significant bioindicators are:
  • sea vegetables: Fucus vesiculosus, brown algae and other benthic algae are among the most sensitive bioindicators and are often used to gauge weapons fallout contamination and nuclear reactor pollution from many radionuclides which these media will readily absorb.

  • The terrestrial counterpart to sea vegetables as sentinel organisms are lichens, moss, mushrooms, and grass. Leafy vegetables such as spinach are examples of bioindicators which humans consume directly and which quickly absorb foliar deposition of radiocesium as well as the short-lived radioiodine-131 (1/2T = 8.04 d.). Milk and milk products, as food crop products of the forage-livestock pathway, are bioindicators which concentrate the rapid transfer of radioactive contamination following nuclear accidents and releases. The presence of iodine-131 in milk is a key indicator of the magnitude of a nuclear accident.

  • benthic invertebrates: Mussels (mytilus edulis, c. virginica, etc.) are another group of sensitive bioindicators and are also used to evaluate the impact of other types of chemical fallout (see U.S. Mussel Watch sec. 5b).

  • fish: Less sensitive than benthic algae (sea vegetables) as bioindicators, fish are an important indicator of the level of human consumption of radioactive contamination. Freshwater fish often show much higher levels of the bioaccumulation of radionuclides and other forms of chemical fallout than marine specimens.

  • grazers: reindeer, sheep, goats, and livestock: Products from these participants in the forage-livestock pathway - reindeer (meat), sheep (mutton), goats (cheese and milk), and cattle (milk and meat) - often exhibit rapid bioaccumulation of radioactive contamination.
CUMULATIVE FALLOUT INDEX: The most important resource for information about the historic accumulation of radioactive contamination from weapons testing and the Chernobyl accident is the database compiled by the RISO National Laboratory in Denmark. The extensive databases compiled by the United States government, especially those compiled by the U.S. Department of Defense via the National Imagery and Mapping Agency (NIMA), are all classified information and not available to the general public. The following data compiled by the RISO National Laboratory provides important baseline data for evaluating the significance of fallout derived from the Japan disaster. Atomic weapons testing began in the early 1950s; the RISO National Laboratory database provides summaries of the annual and cumulative deposition of both strontium-90 and radiocesium. The accidents at Chernobyl and in Japan released, or will release, proportionally more radiocesium and less radiostrontium than weapons testing; therefore, the database of radiocesium deposition is referenced in this accident guideline synopsis. The RISO National Laboratory measured fallout in three locations, Denmark, Jutland, and the Faroe Islands. The cumulative fallout for selective years is reproduced below. Note the peak year for weapons testing fallout was 1963 with rapidly declining fallout levels after 1965 until the Chernobyl accident in 1986. Note that the annual (DI) and the cumulative (Al) fallout are reported in becquerels/m2.

CUMULATIVE REACTOR AND SPENT FUEL POOL INVENTORIES: The most disturbing aspect of the accident at the Fukushima Daiichi complex is the huge inventory of anthropogenic radioactivity at risk of being dispersed into the biosphere. The unfolding disaster in Japan involves the possible meltdown of three nuclear reactors and their fuel assemblies. Even more disturbing is the fact that as many as four spent fuel pool inventories and, possibly as many as six, may also undergo meltdown and dispersal. The most optimistic scenario is that neither the three reactors nor the four spent fuel pools will experience a full meltdown. It is not yet possible to predict what is going to occur at the Fukushima reactor sites. It is important to note that the Daiichi spent fuel pool inventories are located next to and slightly above the reactor vessels of each Fukushima Daiichi power plant reactor. These spent fuel pools contain approximately five to eight times the amount of isotopes as the reactor vessels themselves. Total inventory of radiocesium in the three reactor vessels and the four spent fuel pools involved, or potentially involved, with this disaster range is +/-40,000,000 Ci of Cs-137. The 3/18/2011 edition of the New York Times contained a detailed description of the location of the reactor and spent fuel pool assemblies at risk in this accident. Fortunately, there are a large number of fuel assemblies in a nearby storage unit at Fukushima Daiichi that do not appear to be at risk for meltdown and release during this accident. (See NYT excerpt above.) If the cooling water is lost at spent fuel pools five and six, the quantities of radiocesium available for release could be above 75 million curies.

US DOE SPENT FUEL AND RADIOACTIVE WASTE INVENTORIES: The US DOE Integrated Database for 1992: U. S. Spent Fuel and Radioactive Waste Inventories, Projections, and Characteristics provides a now classified database with information that can be easily interpreted by a layperson to evaluate potential releases at the Japan facilities. As with the RISO National Laboratory reporting system, the DOE tabulated both the annual and cumulative radioactivity produced at America’s 104 light water reactors. 1992 was the most recent year that data was available pertaining to inventories of biologically significant radioisotopes in U. S. nuclear reactors. The following summary is extracted from Vol. 3 of Biocatastrophe the Legacy of Human Ecology, a publication sponsored by the Davistown Museum, and is available from in paperback and eBook. In turn, this summary was extracted from Davistown Museum Special Publication 47 (3/21/2007) which is a reprint of the Oak Ridge National Laboratory database (October 1992) (DOE/RW-0006, Rev 8).

Source: U.S. Department of Energy. (October 1992). Integrated Data Base for 1992: U.S. Spent Fuel and Radioactive Waste Inventories, Projections, and Characteristics. Oak Ridge National Laboratory, Oak Ridge, Tennessee.

The cumulative inventory of radioactivity at U. S. nuclear reactors is summarized in the far right hand column for the most biologically significant isotopes in a nuclear reactor inventory. These inventories express the contents of the spent fuel pools accumulated over the lifetime of reactor operations; they do not include the inventories within operating nuclear reactor vessels. A thumbnail estimate of reactor vessel inventories would be about 10% of the cumulative spent fuel pool inventory. Taking radiocesium as an example, the 1992 total spent fuel pool inventory at U. S. reactors was 1.75E +09, or 1,750,000,000 curies. In 1992, there were 104 operating reactors in the U. S.; a thumbnail sketch of current inventories of radiocesium at U. S. reactors can be obtained by dividing the cululative inventory by 100, providing an approximate estimate of 17,500,000 curies of radiocesium at each U.S. reactor site. During the interim between 1992 and 2011, most U. S. reactors will have accumulated much more than this baseline figure considering that the radioactive decay rate of radiocesium (1/2T= 30.07 years) is much less than the annual productivity of any given reactor. The same observation applies to the cumulative inventory of radiocesium and other biologically significant isotopes at the Fukushima Daiichi facility. Therefore, with three reactor vessels and as many as four spent fuel pools at risk of catastrophic meltdowns, there is at least 4,000,000 curies of radiocesium available for discharge. The reactors at the Japan facility were designed and produced by General Electric and are the same boiling water reactor design as used in 44 aging United States nuclear reactors. In this context, a conservative estimate of the maximum releases of other biologically significant isotopes at Fukushima Daiichi can be obtained by dividing the cumulative inventories listed above in the Oak Ridge database by 20. Potential releases of plutonium-239, not including the extra inventories of plutonium in the number three reactor using MOX fuel, could be reasonably estimated at 20% of 7,080,000 curies, or 1,416,000 curies of the highly toxic alpha emitting plutonium-239. Other websites, including the Union of Concerned Scientists, have already posted extensive commentary on the design history and flaws of the Fukushima Daiichi reactors and US boiling water reactors. Comments on our preliminary estimates of the cumulative radioactivity available for release at the Fukushima Daiichi facilities are welcomed.

ACCIDENT TIMEFRAME: The duration of the Fukushima Daiichi accident is a key unknown that will greatly influence the amount of radioactivity released. After nine days, the “corium” of the Chernobyl graphite reactor melted and flowed into the lower regions of the reactor building and then solidified. “The decay heat dropped due to the uptake of surrounding materials (the stainless steel and serpentine corners of the lower biological shield) combined with rapid spreading of the melted fuel up to 40 meters from the epicenter of the melted corium.” (Sich, A.R. 1996. The Chernobyl active phase: Why the “official view” is wrong. Nuclear Engineering International. 40(501). pg. 22-5.) The unfolding nuclear disaster at the Fukushima Daiichi reactor site in Japan is unlikely to be characterized by the accidental and unexpected sudden decline of the decay heat, which is the key element of any loss of reactor coolant accident (LORCA). (On Wikipedia there is no listing for LORCA; loss of reactor coolant accidents are now defined as LOCAs, loss of coolant accidents. Both the editor’s horse and his air conditioner have recently had loss of coolant accidents. The horse survived, the air conditioner didn’t.) Loss of coolant accidents are now underway outside of the Fukushima Daiichi reactor vessels in the adjacent spent fuel pools.

CHERNOBYL SOURCE TERMS: Source term refers to the quantity of isotopes released during an accident. The following Chernobyl accident release inventories are contained in the RISO National Laboratory’s 1994 report by A. Aarkrog. It is important to note that the potential source term (release inventory) of the Fukushima Daiichi disaster could be as much as ten times that released from Chernobyl.


CHERNOBYL FALLOUT IN THE US: U.S. Nuclear Regulatory Commission. (1987). Report on the accident at the Chernobyl nuclear power station. Report No. NUREG-1250, Rev. 1. Government Printing Office, Washington, D.C. contains very little media specific data on Chernobyl fallout. It does, however, contain some important specific data for fallout at one U.S. site in Chester, NJ, (5/6/86-6/2/86) reported in picocuries per meter2:
  • 131I: 2,380 pCi/m2 (88 Bq/m2)
  • 137Cs: 650 pCi/m2 (24 Bq/m2)
  • 134CS: 290 pCi/m2 (11 Bq/m2)
  • 103Ru: 720 pCi/m2 (27 Bq/m2) (pg. 8-3)
This obscure report on the very distant accident at Chernobyl may help to provide some perspective to possible future fallout levels in the United States from the Japanese disaster. It is certainly possible that the San Joaquin Valley in California, or midwest corn and wheat growing areas, could receive similar or even greater levels of fallout from Japan. Such low level fallout would be reported as of no significance, but would also result in uptake of detectable levels of contamination in many food products. The health physics significance of low level contamination in the food supply would obviously be a controversial topic, assuming accurate information ever became available to the general public.

CHERNOBYL RADIOACTIVITY IN TURKISH TEA: During and following the Chernobyl accident, spiraling plumes of reactor-derived radioactive contamination were distributed over wide areas of the northern hemisphere, including locations thousands of kilometers from the accident site. The eastern Black Sea region of Turkey was the location of a rainfall event that brought extensive contamination to farmlands in which various agricultural crops, including hazelnuts and tea, were grown. Accident-derived cesium 137 were detected in hazelnuts in a range of 2000-2500 bq/kg. Even larger quantities of radiocesium followed the potassium cycle and were reported in Turkish tea in quantities ranging from 1,064 to 44,000 bq/kg (Gedikoglu, Sipahi, Health Physics, v. 56 1989). The ratio of radioactivity transferred to brewed tea was 65%. The documentation of Chernobyl radioactivity in Turkish tea provides a model for what could occur in areas downwind from Japan in a worst case scenario. The challenge for the general public in the age of information technology, in the event of a catastrophic accident in any location, is to obtain media-specific data recorded in now-standard reporting units of becquerels per liter or per kilogram, and to have access to information databases that allow rational evaluation of this contamination. Political and corporate interests may make data-specific information difficult to obtain through most mass media outlets.

ANCIENT HISTORY: FALLOUT CONTAMINATION IN MILK: In 1976, a Chinese atmospheric weapons test produced a significant pulse of radiostrontium that was picked up by the US EPA/ERAMS (Environmental Protection Agency/Environmental Radiation Ambient Monitoring System). Peak values of 41 becquerels per liter (1,120 picocuries) were recorded in raw milk from dairies in Amherst and Montague, MA (10/10/76). Mixed milk from a variety of sources being sold in Boston area grocery stores had radiostrontium contamination levels of less than 20% of the raw milk values from western MA. The passing plume of weapons-derived contamination had its maximum impact on October 10-11. Within 15 days, contamination levels at the dairies had dropped to 8 bq/liter and continued to fall after that. At the time of the plume passage, MA State agencies ordered dairies to switch to stored feed to allow time for the dissipation of the radiostrontium. Needless to say, this information was not made public until later publication (Simpson, Shuman, Baratta, Tanner. 1980. Radiation Data Reports?). Unfortunately, in the unfolding situation in Japan, multiple point sources have the potential to create plumes of contamination that may last for months before the accident is remediated.

JAPANESE REACTOR DESIGN AND FINANCING: It should be noted that the General Electric Corporation, current owner of NBC News, provided the design for construction of the reactor group installed at the Fukushima Daiichi site. Thirty five of these boiling water reactors are located in the United States. Essentially a low budget “subprime reactor design,” the GE facility included the negligent installation of spent fuel pools adjacent to and slightly above the reactor vessels. These reactors, the construction of which provided extensive profits to Wall Street investors, give an ominous new meaning to the term “subprime real estate.”

VESTED INTERESTS AND MEDIA INFORMATION CONTROLS: The unfolding nuclear disaster at the Fukushima Daiichi reactor complex raises the following issues. Unless the unfolding disaster is quickly stopped in the next few days by the resumption of reactor vessel and spent fuel pool cooling, massive quantities of disbursed, biologically significant, accident-derived isotopes will be entering the food chain via ground deposition in locations such as the San Joachim Valley and Midwestern wheat, soy, and corn fields. Vested corporate and banking interests will likely make every attempt to curtail, interrupt, contradict, or obfuscate data, which should be reported as becquerels/kg, becquerels/square meter, or becquerels/liter, documenting contamination of America and the world’s food supply. The candid documentation of the contamination of America's or the world's food supply is unlikely. This observation also applies to future accidents and other locations. In the case of Fukushima Daiichi, this tragic soap opera may play out for years, possibly even decades, after the actual accident comes to an end. It should be noted that the peak pulse of Chernobyl-derived radioactive contamination in foods imported to the U.S. occurred 12 to 18 months after the accident stopped. Even more disturbing is the fact that the United States mainstream media, including the Public Broadcasting Network, withheld information about or suppressed reporting on the contamination pulse that was documented in the annual U.S. FDA imported foods survey. Initially withheld by the federal government, but then obtained by the Center for Biological Monitoring via a Freedom of Information filing, the editor of this accident synopsis spent a week negotiating a story with David Harris of the Public Broadcasting Network before the story was suppressed by Public Broadcast executives who feared the response of network sponsors who might suffer lost revenues and profits from revelations pertaining to contamination of imported foods.
The following information is excerpted from the Center for Biological Monitoring archives. No new information has been posted in this archive since the beginning of 2000. However, the issues, database, editorial comment, and fallout levels are relevant to the nuclear disaster in Japan. Introduction RADNET EDITORIAL COMMENTS As a preview to the annotated citations pertaining to Chernobyl-derived fallout, the editor of RADNET offers the following comments and observations:
  • Nuclear safety experts had not anticipated that a nuclear accident would release this large an inventory of radionuclides.

  • These nuclides were dispersed further, more erratically, and in much greater quantities than had been anticipated prior to the accident. At the time the accident was occurring, and during the weeks and months that followed, there was a widespread lack of accurate information about the seriousness and the radiological impact (deposition levels) of the accident.

  • During and after the accident, official information sources ranged from unreliable (Russian and French government sources) to inaccurate (IAEA, National Radiological Protection Board, etc.). Political considerations and partisan prejudice in favor of nuclear energy production combined with the lack of environmental monitoring information and skewed objective accident analysis with the result that the impact of the accident was and continues to be minimized.

  • This underestimation of the extent of the Chernobyl accident continues today in most official versions in terms of where and in what quantity deposition from the accident occurred.

  • Only a few locations were equipped with sufficient instrumentation to make accurate real-time nuclide-specific measurements of the passage of the fallout cloud and its erratic rainfall-associated deposition.

  • Rainfall events were the fundamental mechanism responsible for the extremely high deposition levels in some locations, including areas located thousands of kilometers from the accident site. Dry deposition played a lesser role in the spread of Chernobyl fallout than in weapons testing fallout events.

  • Only a minimum of information has been collected about the actual levels of the dietary intake of Chernobyl-derived radionuclides for persons living in areas with high fallout - greater than 1 Ci/km2 (37,000 Bq/m2).

  • The failure to measure accurately the dietary intake of specific population groups in the most affected areas and the general tendency to average dose equivalents over large population groups (including estimating projected deaths as a percentage of hemispheric death rates) are particularly reprehensible.

  • A reconsideration of the accident ten years later can only conclude that accurate information is still unavailable about actual deposition levels over vast areas of the Northern Hemisphere where millions of residents do not have access to accurate radiological monitoring data (Turkey, Iran, Iraq, North Africa, etc.).

  • Even in countries with modest to excellent radiological monitoring capabilities, accurate information about the impact of the accident was not available in a timely manner and, in some cases, has never been made available.

  • The United States serves as an example of the problem of freedom of information. While most areas of the United States received only a minimum of Chernobyl-derived fallout, some locations (See Dibbs, Maryland) received fallout which exceeded weapons testing deposition. The radiological surveillance data collected by the EML (Environmental Measurements Laboratory) and the EPA were either limited to a very small number of locations or, in the case of the EPA, did not include ground deposition data (Bq/m2) or accurate air concentrations expressed in µBq/m3 (microbecquerels).

  • Extensive data collected by the National Reconnaissance Office pertaining to the Chernobyl accident is not yet available to the general public.

  • We welcome your comments on our editorial opinions. We also solicit additional citations pertaining to Chernobyl fallout.

  • Articles cited in this section but not annotated were not present at hand for review.

  • We will add citations and data to RADNET as they become available.

  • This section of RADNET combines some editorial content with the data citations.


Fusco, Paul and Caris, Magdalena. (2001). Chernobyl Legacy: Twenty four minutes and zero seconds anti meridian. de.MO, Millbrook, NY.

  • A chilling and moving photo tour of the legacy of the Chernobyl accident.

  • The cesium contamination maps show fallout levels ranging up to 7,400,000 Bq/m2 in a spotty pattern over thousands of square miles to the north and northeast of Chernobyl, with lesser quantities of deposition on the European component of the map found later in the text.

  • The limited written text is poetic, informative, concise and haunting.

NOTICE TO THE READER: Levels of contamination cited within the Chernobyl data base are peak concentrations unless otherwise noted. Ground deposition activities varied widely in most areas impacted by the Chernobyl accident: A location receiving, for example, 40,000 Bq/m2 could be only a few kilometers from another location receiving an order of magnitude less deposition. Nurmijarvi, Finland, a location with real time data collection capabilities, recorded the highest air concentrations of any location cited in RADNET (over thirty Chernobyl-derived nuclides were observed); ground deposition activities at this location, while elevated, were typical of many locations receiving heavy rainfall associated fallout. The data cited for both ground deposition and contamination of abiotic and biotic media which follow are the highest readings in the survey being cited, unless otherwise indicated.
To see the archived Chernobyl citations, follow this LINK.