DEVELOPMENT OF A MELCOR SELF-INITIALIZATION ALGORITHM FOR BOILING WATER-REACTORS

The MELCOR code, developed by Sandia National Laboratories, is suitabl e for calculating source terms and simulating severe accident phenomen a of nuclear powerplants. Prior to simulating a severe accident transi ent with MELCOR, the initial steady-state conditions must be generated in advance. The current MELCOR users' manuals do not provide a self-i nitialization procedure; this is the reason users have to adjust the i nitial conditions by themselves through a trial-and-error approach. A MELCOR self-initialization algorithm for boiling water reactor plants has been developed, which eliminates the tedious trial-and-error proce dures and improves the simulation accuracy. This algorithm adjusts the important plant variables such as the dome pressure, downcomer level, and core flow rate to the. desired conditions automatically. It is im plemented through input with control functions provided in MELCOR. The reactor power and feedwater temperature are fed as input data. The in itialization work of full-power conditions of the Kuosheng nuclear pow er station is cited as an example. These initial conditions are genera ted successfully with the developed algorithm. The generated initial c onditions can be stored in a restart file and used for transient analy sis. The methodology in this study improves the accuracy and consisten cy of transient calculations. Meanwhile, the algorithm provides all ME LCOR users an easy and correct method for establishing the initial con ditions.