Overview and outcomes of the OECD/NEA benchmark study of the accident at the Fukushima Daiichi NPS (BSAF), Phase 2 – Results of severe accident analyses for unit 3

This is the third part of three paper describing accidents at Fukushima Daiichi nuclear power station as analyzed in Phase 2 OECD/NEA project “Benchmark Study Accident Nuclear Power Plant” (BSAF). In this paper, we describe accident progression unit 3. Units 1 and are discussed parts series papers. BSAF project, eight organizations from five countries (CRIEPI, IAE, JAEA NRA, Japan; IRSN France; PSI, Switzerland; SNL, USA; VTT, Finland) severe scenarios for Unit 3 site using different codes (ASTEC, MAAP, MELCOR, SAMPSON, THALES). The present describes findings comparison participants’ results against each other plant data, evaluation final status inside reactors. Special focus on reactor pressure vessel, melt release fission product transport. specific aspects, e.g., complicated following repeated containment venting actuations attempts coolant injection time major core degradation, highlighted points consensus well remaining uncertainties data needs will be summarized. Fission transport analyzed, calculation compared with dose rate measurements containment. I-131 Cs-137 to environment analysis conducted WSPEEDI code.