PEPIN, Methodology for Computing Concentrations, Activities, Gamma-Ray Spectra, and Residual Heat from Fission Products

1 - Description of program or function: The concentrations, activities, gamma-ray spectra and residual heat from fission products can be calculated as a function of time for instantaneous fission or for one or more irradiation steps. 2 - Methods: Using the basic data in the libraries, the PEPIN code solves the differential equations satisfied by the fission product concentrations. Data Libraries: Independent Yields Library: 8 independent yields for 235U, 238U, 239U, 232U, 233U. Chain library: Precursor chain file for 635 nuclides. Gamma-Ray Energies Library: Average beta and gamma-ray energies in increasing order. 3 - Restrictions on the complexity of the problem: The number of nuclides must not exceed 650. The number of Gamma-Rays must not exceed 8500. The number of decay times must not exceed 59. The number of irradiation steps must not exceed 40