PLANT-SPECIFIC RETRAN ANALYSES IN SUPPORT OF CHINSHAN BWR 4 OPERATION/

Two analyses for Chinshan nuclear power station (CSNPS) show the RETRA N applications in reactor operations. One was used to find the root ca use of a reactor trip due to high neutron flux (APRM Hi-Hi). Two of th e Sour turbine control valves failed and closed rapidly. Whether the p ressure increase caused the APRM Hi-Hi reactor scram was questioned. A n analysis was performed to determine the way to bring unit 1 back to power. The second analysis was conducted to provide an evaluation of t he consequences before a plant test planned for late 1994 to consider a design change upgrading recirculation flow control. However, there w ere concerns about reactor scram during execution of the test and the potential of entering the exclusive region of instability. Sensitivity studies on several different combinations of initial conditions and f eedwater flow coastdown curves indicated potential problems with react or trip and stability.