Critical experiments for fuel debris using modified STACY

Izawa, Kazuhiko ; Tonoike, Kotaro ; Sono, Hiroki ; Miyoshi, Yoshinori

Critical assemblies of thermal neutron system are decreasing in number in spite of their important roles in the reactor physics research. On the other hand, the extension of the utilization term of the LWRs brings new research themes requiring critical experiments of thermal neutron system. JAEA is modifying the Static Critical Experiment Facility (STACY) to revive the critical experiments. The modified STACY will be an infrastructure for the experimental research of reactor physics on thermal neutron system. The primary mission of the modified STACY at present is the critical experiments for fuel debris to contribute to the criticality safety control of the fuel debris generated by the severe accident of the Fukushima Daiichi Nuclear Power Station. This report introduces the plan of criticality safety research in Japan Atomic Energy Agency following the accident, and describes the role of the modified STACY in the retrieval work of fuel debris from the damaged reactor.