The OECD-NEA Benchmark Study of the accident at the Fukushima Daiichi Nuclear Power Station

The OECD-NEA BSAF project is aimed to evaluate and analyse the likely end-state of the reactor core after the accidents at the Fukushima Daiichi nuclear power stations. The project will help the TEPCO to plan the removal of components from the reactor containment and the ect concentrated in the accident progression for 6 days after SCRAM and it has concluded in November 2014. A follow-on project, designated as Phase 2, is ongoing. For the Phase 2, the scope of the analysis is extended to include the hydrogen generation and potential for combustion as well as the source term analysis and comparison with the measured activities and dose rates at relevant locations at the plant and in the plant vicinity. In addition, the duration of the analysed sequence will be extended to 20 days from the accident initiation, a task which may prove very challenging to the severe accident analysis tools. Korea, Russia, Spain, Switzerland and United States. Additionally 3 new signatories have joined the project: China, Canada and Finland. The operating agent of the project is The Japan Atomic Energy Agency (JAEA). The project started 2015 and is planned to end in 2018. PSI has successfully participated in the BSAF project Phase 1, represented Switzerland in the project meetings and has contributed to the final and summary BSAF Phase 1 report. Durmain tool for the system level simulation of the sequence. However, the use in the future of other tools which provide a more detailed treatment of hydrogen distribution and fission product behaviour is not excluded. During the present year, the main possible failures of RPV and PCV were identified; therefore the MELCOR 2.1 input has been modified to include such failures. Additionally a proper representation of the fission product release has been included. After the changes a similar sequence Plausible failures of RPV and PCV were preliminary evaluated.