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The 53rd Thesis Award of Atomic Energy Society of Japan

2021.04.14


M. OSAKA, S. MIWA

Dr. Shuhei Miwa of Development Group for LWR Advanced technology, Dr. Masahiko Osaka of Fuels and Materials Engineering Division and Mr. Naoya Miyahara of Development Group for LWR Advanced technology (current affiliation: Mitsubishi Heavy Industry) received the 53rd Thesis Award of Atomic Energy Society of Japan for the paper entitled, “Boron chemistry during transportation in the high temperature region of a boiling water reactor under severe accident conditions Vol.57, No.3, pp.291-300 (2020)”, on 17th March 2021.

The control material boron could be released into the reactor in severe accident of boiling water reactor, and react with cesium and iodine which are important from the view point of exposure and environmental contamination. The changes in cesium and iodine chemical behaviors such as generation of gaseous iodine which is easily released into environment can cause significant influence on their release into environment and distribution in the reactor. Therefore, it is crucial to evaluate the effects of boron on cesium and iodine chemistry. However, there is difficulty in the experiment to evaluate the chemical behavior because the chemical behavior is complex by the effects of the thermal hydraulics and physical behavior during transportation. The authors, therefore, built up the experimental setup, named TeRRa, which can reproduce chemical behavior with grasping the effects of the thermal hydraulics and physical behavior. As the results of experiments with boron using TeRRa, the authors elucidated the important chemical behavior of boron such as high-temperature chemisorption of boron onto stainless steel, and possible capturing of cesium which should be considered in the severe accident analysis.

This result allows the increase of the accuracy in the estimations of release into environment and distribution in the reactor. It is expected to contribute the more accurate evaluation of public exposure and the control of exposure for workers in decommissioning and dismantling of TEPCO Fukushima Daiichi Nuclear Power Station.