TRACE ANALYSIS OF MSIV CLOSURE DIRECT SCRAM EVENT FOR LUNGMEN ABWR

摘要

TRACE (TRAC/RELAP Advanced Computational Engine) model of Lungmen Nuclear Power Plant (NPP) was used to analyze the MSIV (Main Steamline Isolation Valve) closure direct scram transient as defined in Lungmen NPP FSAR Chapter 15. The results were compared with those from FSAR (Final Safety Analysis Report) and RETRAN02. The MSIV closure direct scram transient began with the MSIV of main steam piping closing. The scram signal initiated when the opening degree of MSIV was lower than 85% with the assumption that MSIV were fully closed in 3 sec. After fully closed, the MSIV upstream and reactor pressures increased and the control rod began inserting at about 1.18 sec to keep the core power down. However, four RIPs (Reactor Internal Pumps) not connected with M/G (Motor Generator) Set tripped at around 3.12 sec and the safety relief valve opened at about 3.71 sec according to the increase of reactor dome pressure. This paper compares those important thermal parameters at steady state, such as the dome pressure and temperature of reactor vessel, steam flow, feedwater flow, core flow, and RIP flow, etc.. It also compares the parameters under transient conditions. It was concluded that the steady state results of TRACE calculations are in good agreement with those from RETRAN02. For transient conditions, the comparisons of the results for the parameters indicated that they are in reasonable consistency. In summary, our studies concluded that Lungmen TRACE model is correct for the MSIV closure direct scram transient.