COSIMA, BWR Core Performance Simulator

1 - Description of program or function: A static BWR core simulator suited for performing core follow studies in time steps. Coupled neutronic and hydraulic calculations provide as results Keff and flux-, power-, temperature-, and density distributions. 2 - Method of solution: The (2-group) flux distribution is obtained by the Nodal Expansion method. Neutron cross sections are interpolated from input tables with the following entries: - Fuel type; - Average void during burnup; - Control rod in/out during burnup; - Burnup; - Actual control rod position in/out; - Actual void; - Actual fuel temperature; - Actual coolant temperature. Void, fuel temperature, and coolant temperature are found in the hydraulic part, and iterations between neutronics and hydraulics are performed until convergence. Provisions for detailed pin power reconstruction are included and activated via input instructions. 3 - Restrictions on the complexity of the problem: The size of the problems can be redefined by changing the parameter values stated in the beginning of the COMMON area. The present values are: NCHANM = Max. number of channels (assemblies) = 450; NNODEM = Max. number of nodes = 12000; NZMAX = Max. number of axial nodes = 26; NFTYPM = Max. number of fuel types = 6; NXMAX = Max. number of nodes in x- or y-direct = 32; NGMAX = Max. number of energy groups = 2; NAPMAX = Max. number of expansion order in NEM = 5; NBUSTM = Max. number of burnup steps = 30; NAVVOM = Max. number of average void values = 4; NPINMX = Max. number of fuel pins along assembly edge = 8