[2H01-02] Analysis Method Development 1

[2H02] Study on Criticality Accidents Analysis by Ramp Reactivity Insertion using Multi-region Integral Kinetic code

*Kodai Fukuda¹, Jun Nishiyama², Toru Obara² (1. Nuclear Engineering course, Obara laboratory, Tokyo Institute of Technology, , 2. Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology)

Keywords:Criticality safety, Prompt supercritical transient analysis, Ramp reactivity insertion, Fuel debris, Fukushima Daiichi NPS decommissioning

Transient analysis for criticality accidents of fuel debris is important. In previous studies, Multi-region Integral Kinetic (MIK) code has been used. This is because it can include characteristics of fuel debris properly. In those analyses, stepwise reactivity has been treated because of limitations of the MIK code. The purpose of this study is to clarify possible conditions that can be analyzed by the MIK code when ramp reactivity is inserted.
Preliminary analysis was performed using point reactor kinetics model to reveal applicable range of the MIK code in terms of contribution of delayed neutrons. Supercritical conditions were analyzed and discussed when ramp reactivity was inserted within the applicable range.