Simulator performance upgrade and evaluation of loss of RHR during midloop operation for Maanshan PWR plant

Because a greater risk than expected is introduced during midloop operation for typical PWRs, the performance of training simulator of Taiwan’s Maanshan 3-loop PWR plant was verified and upgraded for midloop operation (MLO) simulation. Besides, plant specific midloop abnormal operation procedure (AOP) also was quantitatively evaluated. Instead of modifying existing RCS module, a thermal-hydraulic code, namely ROSE (Reactor Outage Simulation and Evaluation) has been developed and transplanted into the training simulator of Maanshan PWR plant. A two-region approach with a modified two-fluid model was adopted as the theoretical basis of the ROSE code. The success of the simulator performance upgrade for the MLO was demonstrated by comparisons to W-GOTHIC MLO calculation as well as the original simulator performance. Moreover, regarding the evaluation of the associated AOP for MLO after loss of RHR, the most risky plant configuration as well as associated crucial timing before core uncovery was also identified by the upgraded training simulator.