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Perspective on post-Fukushima severe accident research

Department of Nuclear Engineering, Kyoto University, 615-8540, Japan (
Abstract:After the Fukushima Daiichi accidentin March 2011 several investigation committees issued reports with lessons learned from the accident, in which some recommendations on severe accident research are included. The review of specific severe accident research items had already started before Fukushima accident in working group of Atomic Energy Society of Japan (AESJ) in terms of significance of consequences, uncertainties of phenomena and maturity of assessment methodology. Re-investigation started after the Fukushima accident in this working group to cover additional effects of Fukushima accident, such as core degradation behaviors, sea water injection, containment failure/leakage and re-criticality. The review results are categorized in nine major fields; core degradation behavior, core melt coolability/retention in containment vessel, function of containment vessel, source term, hydrogen behavior, fuel-coolant interaction, molten core concrete interaction, recriticality and instrumentation in severe accident conditions. In January 2012, in collaboration with this working group, Research Expert Committee on Evaluation of Severe Accident was established in AESJ in order to investigate severe accident related issues for future LWR development. Based on these activities and also author’s personal view, the present paper describes the seven important severe accident research issues after Fukushima accident. They are (1) investigation of damaged core and components, (2) advanced severe accident analysis capabilities and associated experimental investigations, (3) development of reliable passive cooling system for core/containment, (4) analysis of hydrogen behavior and investigation of hy6drogen measures, (5) enhancement of removal function of radioactive materials of containment venting, (6) advanced instrumentation for the diagnosis of severe accident and (7) assessment of advanced containment design which excludes long-term evacuation in any severe accident situations. Lastly severe accident research conducted at Kyoto University is briefly introduced.
Keyword: severe accident; Fukushima Daiichi; research issues; lessons learned
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