SCORCH-B2, BWR Core Heating During LOCA

1 - Nature of physical problem solved: SCORCH-B2 is a simulation code of reactor core heatup during a LOCA of BWRs. The program analyzes transient heat transmission on a horizontal plane of a fuel assembly and evaluates the peak cladding temperature and the maximum oxide thickness, both of which determine the soundness of the core during the accident. Fuel rods are arbitrarily classified into a smaller number of groups and each fuel rod is divided into several annuli. Heat conduction within fuel rods, heat convection from rods to coolant and radiation among rods and the channel box are calculated for each time step. 2 - Method of solution: Forward explicit differential method is used to solve the heat transmission equations and the shadow area method which was newly developed is used to calculate the radiation view factors between ballooning rods. 3 - Restrictions on the complexity of the problem: The maximum number of columns (= number of rows) of the fuel rods in a fuel assembly is 8. The maximum number of radial nodes in a fuel pellet is 10. Any grouping of rods in an assembly is applicable