The Impact of Thermal-Hydraulic Information on Nuclear Fission Product Behavior Simulation Using the SIRIUS Module in the CINEMA Code

Abstract

The Code for Integrated Severe Accident Evaluation and Management (CINEMA), a comprehensive national code for severe accident analysis, was developed and improved in Korea to simulate the presumed progression of the accident of light water reactor systems. The CINEMA code consists of four key modules to simulate different accident events, including CSPACE (Core meltdown progress simulation coupling with Safety and Performance Analysis CodE) for in-vessel phenomena, SACAP (Severe Accident Containment Analysis Package), SIRIUS (SImulation of Radioactive nuclide interaction under severe accident), and MASTER, which facilitates coordination between individual modules. The study focuses on identifying suitable options for generating thermal-hydraulic data files necessary for future uncertainty analysis of SIRIUS systems using independent calculation. The simulations were conducted for a duration of 72 hours, focusing on a large break loss of coolant accident (LBLOCA) scenario in the Optimized Pressure Reactor 1000 (OPR1000). Analysis was conducted by altering the input conditions of thermal-hydraulic data file, specifically the STEP and TIME conditions, to investigate the influence of the SIRIUS module on nuclear fission product behavior simulation. The results show that an increase in the size of the STEP or TIME option in suspended aerosols resulted in an increase in the maximum amount of suspended aerosol, and the maximum value increased exponentially with increasing option size. Upon analyzing the differences in results stemming from the selection of the STEP and TIME options, it was observed that initially, both options yielded nearly similar and stable computational outcomes.