Toward Improved Understanding and Analysis of the Fukushima Nuclear Accident

Sammanfattning

This research uses the MELCOR code to conduct an analysis of the severe accident which oc-curred at Unit 1 reactor of Fukushima Daiichi Nuclear Power Station (FDNPS), with a focus on source term estimation during the accident progression. The MELCOR model of FDNPS Unit 1 (1F1) was provided by the Swedish Radiation Safety Authority (SSM) and revised to accommodate some latest understanding of the accident and modeling development.The MELCOR simulation covered the period from the onset of the station blackout through the hydrogen explosion and subsequent containment depressurization, extending to 11 days (270 hours). The present study employed the representative radionuclides 137Cs and 131I in the source term to characterize release magnitude (as a percentage of the initial inventory and in activity), release timing, and release altitude. The results were compared with previous studies and measured on-site data to assess the validity of the simulation.