Research program for the evaluation of fission product release and transport behavior focusing on FP chemistry

A new research program on severe accidents has been launched for the evaluation of FP release and transport behavior in the BWR system. The purpose of the program is to improve the FP release and transport model using the experimental database of FP chemistry focusing on Cs and I chemistry. In this program, the effects of B including control rod materials, B₄C for the Cs and I chemistry are considered. Postulated behaviors in the BWR system for Cs, I, B release and transport are classified into 4 processes based on typical BWR severe accident scenarios. The experimental database used for improvement will consist of results obtained with a newly-prepared test device under an atmosphere with broad-ranging oxygen and/or steam partial pressure simulated in the BWR. The state of preparation for these experimental studies and analyses is introduced. In addition, preliminary testing was initiated to show B chemical effect on Cs and I transport under one of the processes; namely deposited Cs compounds, B vapor and aerosol interaction. In this experiment, 'B stripping effect' to deposited CsI was observed. (author)