A separate effect test on the cooling behavior in a pressurized water reactor core under a low reflooding rate condition by using ATLAS and RELAP5/MOD3.3 code assessment

摘要

A separate effect test was performed on the cooling behavior in a PWR core under a low reflooding rate condition by using the ATLAS (Advanced Thermal-Hydraulic Test Loop for Accident Simulation) which is a thermal-hydraulic integral effect test facility for the pressurized water reactors APR1400 and OPR1000. Although several integral tests for the reflood phase of a large break loss of coolant accident (LBLOCA) of APR1400 have been performed with the ATLAS, the previous integral effect tests for the reflood phase of a LBLOCA are not easily simulated by existing codes, such as the RELAP5/MOD3, due to a unique phenomena in ATLAS, that resulted from an injection of large amount of subcooled water onto the heated wall of which temperature was higher than the target value. Therefore, there is a need to perform a separate effect test under a low reflooding rate condition using the ATLAS to help validate the RELAP5 reflood models. The present LB-CL-15 test was performed to validate the RELAP5 reflood models for a core quench phenomenon under a low flow rate ECC injection condition. Separate effect test data for APR1400 could be obtained by using the ATLAS, which could simulate a direct vessel injection, a reverse heat transfer from steam generators and the steam binding effect, etc. The experimental data were used to assess the reflood models of the safety analysis codes of the original RELAP5/MOD3.3 and a modified version of RELAP5/MOD3.3. The modified version showed better agreement with the test data than the original version. 【keyworks】ATLAS;Separate effect test;LBLOCA;Reflood;APR1400;Core cooling