Study and assessment of the newly proposed passive management of MSLB + SBO accidents for the VVER 1000/V446 NPP using the secondary side Deaerator tank

Abstract

To manage accidents in actual conditions, we need to evaluate different accident scenarios on nuclear power plants. Removing the residual heat from the reactor core after the loss of off-site power (LOOP) accident and Station black-out (SBO) accident is one of the biggest challenges in such an incident. In this paper, LOOP and SBO Accidents with the main steam line break (MSLB) accident of No. 2 (inside the Containment) have been simulated by the thermal-hydraulic RELAP5 code on the VVER-1000/v446 reactor. A total of 5 different scenarios have been simulated, assuming the most difficult conservative conditions, and the results reveal the critical role of diesel generators in supplying emergency feed water pumps (EFWP), as well as the part of operator performance in securing a nuclear power plant in the condition of an accident. In the case of using a series of operator operations and using the water resources of the Deaerator tank on the secondary side with the Feed and Bleed system on the primary side, in The most brutal conservative mode (MSLB + SBO accident) by injecting the water into the steam generator-4, the temperature and pressure of the coolant in the primary side are reduced and by absorbing more heat from the reactor, core melting is delayed about 25,000 s, and the safety of Bushehr nuclear power plant (BNPP) against this accident will be improved.