Identification of important phenomena through the PIRT process for development of sodium fire analysis codes

Abstract

JAEA has developed sodium fire analysis codes, SPHINCS and AQUA-SF, to evaluate the consequences of sodium fire events, which are a key issue in sodium-cooled fast reactor (SFR) plants. This paper describes a PIRT (Phenomena Identification and Ranking Table) process for such events. The present PIRT can be utilized to validate the sodium fire analysis codes. Because a sodium fire event in an SFR plant involves complex phenomena, various figures of merit (FOMs) for importance ranking could exist in the PIRT process. Therefore, the FOMs are specified through a factor analysis. Associated phenomena in a sodium fire event are identified through both element- and sequence-based phenomena analyses. The importance of each associated phenomenon is evaluated by considering the sequence-based analysis of associated phenomena related to the FOMs. Then, a ranking table for the event is established. An assessment matrix of important phenomena and experiments is completed. Sufficiency of experimental data is confirmed for the validation of models corresponding to the identified important phenomena in the sodium fire analysis codes. Additional assessments are discussed specifically for the aerosol module and the CFD module in three-dimensional codes from a perspective of careful validation.