RELAP5 code study of ROSA/LSTF experiment on a PWR station blackout (TMLB') transient

PWR全交流電源喪失事象に関するROSA/LSTF実験のRELAP5コードによる解析的研究

竹田 武司 ; 中村 秀夫  

Takeda, Takeshi; Nakamura, Hideo

RELAP5 code analysis was performed on one of abnormal transient tests conducted with the ROSA/LSTF simulating a PWR station blackout transient with TMLB' scenario in 1995. The LSTF test revealed core uncovery by core boil-off took place a little after hot leg became empty of liquid. The code indicated remaining problems in the predictions of reverse flow U-tubes in SG during long-term single-phase liquid natural circulation. Sensitivity analyses were performed to clarify effectiveness of depressurization of and coolant injection into SG secondary-side as accident management measures. SG secondary-side depressurization was initiated by fully opening the safety valve in one of two SGs with incipience of core uncovery. Coolant injection was done into the secondary-side of the same SG at low pressures considering availability of fire engines. The SG depressurization with the coolant injection was found to well contribute to maintain core cooling by the actuation of accumulator system.