The Status of the Japanese project on material accountancy of fuel debris and U.S.-Japan cooperation on survey of technologies for nuclear material accountancy at Fukushima Daiichi Nuclear Power Plant

Hori, Keiichiro; Heinberg, C.; Conner, J.*; Browne, M.*; Colin, C.*

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At the time of accident, about 270 tons of fuel were in Units 1- 3 at Fukushima Daiichi Nuclear Power Station. Up to that time, material accountancy was implemented as an item facility for adequate material control and for the International Atomic Energy Agency's safeguards verification. Fuel debris contains nuclear fuel materials, fission products and structural materials, etc. Fuel debris will need to be controlled adequately after removal from the reactors, but material accountancy measures as an item facility no longer can be applied because of meltdown of the fuel. Development of measurement technologies for fuel debris may be required for adequate material control and accountancy of special nuclear material in the fuel debris at Fukushima Daiichi. Japan Atomic Energy Agency (JAEA) and United States Department of Energy/National Nuclear Security Administration (DOE/NNSA) have agreed to collaborate to investigate past experience on material control at severe accidents involving reactor core fuels and potential measurement technologies for fuel debris measurement. Besides DOE/NNSA and JAEA, Japanese Government, Tokyo Electric Power Company (TEPCO), Central Research Institute of Electric Power Industry (CRIEPI) and the U.S. National Laboratories have been collaborating in this effort. This paper describes the purpose, objectives, structure and process of this collaboration.