Evaluation of important phenomena through the PIRT process for a sodium fire event

Sodium fire is one of key issues in sodium-cooled fast reactor (SFR) plants. JAEA has developed sodium fire analysis codes, a zone model code SPHINCS and a field model code AQUA-SF, to evaluate the consequence of sodium fire events. This paper describes a PIRT (Phenomena Identification and Ranking Table) process for sodium fire events. Ranking table for important phenomena and an assessment matrix are completed. Because a sodium fire event in an SFR plant involves complex phenomena, the ranking table has been established through both element- and sequence-based phenomena analyses in addition to the engineering judgement. The assessment matrix confirms sufficiency of experimental data for validation of models corresponding to the identified important phenomena in the sodium fire analysis codes. As a part of comprehensive validation based on the assessment matrix, an experimental analysis for a large-scale sodium spray fire experiment Run-E1 is conducted by using the SPHINCS and AQUA-SF codes. The analytical results of the both codes show good agreements with the experimental data of gas pressure transient. Difference from the experimental result of the maximum pressure are about 5% smaller in the SPHINCS code and about 10% larger in the AQUA-SF code. General validity for the codes would be confirmed through the comprehensive validation based on the assessment matrix.