Nuclear Disaster in Japan
Introduction
This blog is sponsored by the Davistown Museum in Liberty, Maine, (http://www.davistownmuseum.org/) 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 amazon.com 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 curator@davistownmuseum.org. 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, wikipedia.org, 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.
- 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)
- 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 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)
- 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)
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 (http://www.epa.gov/rpdweb00/rert/pags.html) 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)
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. (wikipedia.org/wiki/Banana_equivalent_dose).
- 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
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.
- "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)."
| intervention level of dose (Sv) | |
| DIL (Bq/kg) = | |
| f x Food Intake (kg) x DC (Sv/Bq) |
- 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
- 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.
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.
- 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
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
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: http://lockerz.com/gallery/9699108
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:
Dr. Ryugo Hayano of Tokyo University's Compiled Timelines -- Timelines of radiation data on Twitter, same data on Lockerz here: http://lockerz.com/gallery/9699108
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:
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
RadiationNetwork.com -- 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
Weather.co.uk'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.
CONVERSION FACTORS:
- 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.
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 ACCIDENT SCENARIOS:
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 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 amazon.com 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.
CONVERSION TABLES: See RADNET.
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. 
Excerpt:
To see the archived Chernobyl citations, follow this LINK.
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.
Excerpt:
Fusco, Paul and Caris, Magdalena. (2001). Chernobyl Legacy: Twenty four minutes and zero seconds anti meridian. de.MO, Millbrook, NY.
|
| 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. |
- THANX .... & keep-up the good 'work', Richard
ReplyDeleteThank you! I hate that it's so difficult to measure what we are ultimately ingesting!They need to throw sand on those reactors now, today, this minute! They are criminals now to so many people - so many people are the end victims of this crime that may never be put up to trial...they should be providing people in fallout areas with masks, protective suits, seaweed...GE or the Japanese power company could help us - the wall street investors could sell a yacht and buy everyone protective gear...it is their past and present actions, they are responsible for everything that is resulting all over the globe, for every case of breast cancer in 15 years, for every life shortened, for every case of emotional trauma from trying to keep safe from invisible, difficult to measure and life threatening radioactive particles. They are responsible for all of it.
ReplyDeleteEnjoyed a quick review of this important piece of work. I will forward on to some experts in the field for further commentary. Thank you for suggesting I read this very complete and thorough analysis. Although the units of measurement of absorbed dose and exposure remain confusing to most individuals this work really attempts to explain the way radiation is measured and it's significance to the world. We can only hope the current disaster can be contained and limited, but this looks very problematic at this point. Bob.
ReplyDeletei have been closely following all media, print and online and major news publications and have searched in vain for the kinds of explainations that i have found here...and thanku for making it real, genuine and yet detailed and relevant; i know just from internal 'watching' of the main cable and news networks..that they have both dropped off the map if not the world, in terms of making experts available to the watching world; they began to do so, near the end of the first week of reporting and then it simply failed...libya and brazil became more important than a massive worldwide radialogical event ....and Pres Obama and Wall Street and GE took control ...as soon as the West Coast monitors lit up.....even so, your report here is just what i felt filled a critical gap, that i have been searching the net world over for....thanku...it may just help me..not just save my only nine yr old son...but it may help me....write very powerful emails to my Senators and Congressmen and some folks who call themselves leaders...
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What has happened in Japan is a horrific outcome of building nuclear powered reactors in places of highly related zones of natural disasters. Whoever thought it would be a good idea to place a nuclear reactor here must have been out of their mind from not taking their iodine supplements. Pretty sure this accident will stem to be featured on sites such as this: http://www.top10thingsblog.com/2012/05/24/top-10-worst-natural-disasters-world-date/
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