RELAP5 Modeling Of AP1000 Nuclear Power Plant LB-Loca Analysis And Application

As the newly-designed third-generation nuclear power plant, AP1000 has many engineering design characteristics contributing to reactor safety, which are very important for us to study. Besides, in 1998, the 10 CFR 50.46 rule allowed the use of realistic physical models to analyze loss-of-coolant accident (LOCA), of which the execution of various realistic LOCA transient simulations is applied, where the effect of both model and input uncertainties are ranged and propagated throughout the transient. According to the LBLOCA results calculated by Westinghouse, the calculated PCT is near to the safety regulation line. As a result, initial plant status uncertainty analysis should be carried out to obtain a greater thermal margin.To investigate the design features of AP1000, RELAP5 was applied to model the NSSS of AP1000 and it was utilized to systematically perform the analysis of LBLOCA.After that, based on the AP1000 LBLOCA model, characteristics of passive design,the effects power up-rate and RCP shutdown time on LOCA are also analyzed. At last, to evaluate the effect of plant status uncertainty on PCT, Westinghouse advanced thermal hydrolic method ITDP (Improved thermal design procedure) is applied to statistically quantify the effect of plant status uncertainty, thus we can get a lower calculated PCT to improve the plant economy.A comparison between the RELAP5 model of AP1000 and the Westinghouse LBLOCA results was made to verify the AP1000 RELAP5 model. It was also found that (1) the fail of IRWST could lead to the nuclear core re-exposure, which occurs about 17000s after break; (2) the PCT of LBLOCA will increase about 15K with every 1% increase of AP1000 power; (3) after sensitivity analysis and quantification of the plant status uncertainty, a greater PCT margin can be provided by 30~50K than traditional conservative bounding status LOCA analysis.