Thursday, October 27, 2011

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?

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