高速炉の炉心損傷事故起因過程解析コードによる炉内試験解析,4; EFM1試験の解析

Analyses of in-pile experiments by an analysis code on initiating phase of core disruptive accident in sodium cooled fast reactors, 4 Analysis of EFM1 test

今泉 悠也 ; 深野 義隆  

Imaizumi, Yuya; Fukano, Yoshitaka

本研究では、炉心損傷起因過程解析コードSAS4Aを用いて、国際共同CABRI炉内試験のうち、EFM1試験の解析を行った。EFM1試験では、流量減少による冷却材沸騰及び被覆管溶融の後に出力パルスを印加している。本試験では、燃料溶融後も核加熱が継続しているため、溶融燃料の大幅な移動と再固化が観察されており、解析におけるそれらの挙動の再現性も焦点の一つとなる。試験解析の結果、冷却材沸騰のタイミングや沸騰領域の拡大、また燃料の溶融移動挙動等について、実験結果との良好な一致を確認することができた。

The test result of EFM1 in the CABRI in-pile experiment which was conducted as an internationally collaborated project was analyzed by SAS4A code. The code was developed for the analysis of initiation phase of core disruptive accident. In the EFM1 test, transient overpower was imposed after the cladding melting and coolant boiling which was due to the previously imposed loss of flow. The behavior of large relocation and refreezing of the molten fuel which was caused by the heating peak after the fuel melting was one of the important point in the analysis. As a result, good agreements were observed between the results of experiment and analysis such as timings of coolant boiling, extension of boiling area and behavior of molten fuel motion.