RASPA, Burnup with Fission Products Inventory, Gamma Spectra, Isotopic Power Density

1 - Nature of physical problem solved: The program calculates the build-up, decay and burnup of fissionable isotopes and their fission products. It calculates for variable time steps the concentrations, the decay heat, the total burnup, the gamma spectrum in any energy groups and the power density of the isotopes. 2 - Method of solution: The time dependent variations of the concentrations are described by a system of linear ordinary differential equations of first order with constant coefficients (if the flux is held constant). This system is especially easily solved in the case of a triangular matrix of the coefficients. Such a triangular form is attainable by: (1) Restriction to reactions of the following kind: (a) fission; (b) (n,gamma) reaction (capture); (c) beta decay; (d) gamma decay of the excited states of the nuclei. (2) Arrangement of the isotopes in a special order. This means neglecting reactions of the kind (n,alpha), (n,2n), emission of neutrons (formation of delayed neutrons) and similar processes which are in general of less importance. 3 - Restrictions on the complexity of the problem: The code is zero- dimensional. The data of a reactor core or a zone of it must be represented by adequate average values. Further restrictions are: - only reactions as indicated in section 4 are taken into account; - number of fissionable isotopes lower or equal to 15; - number of fission products and fissionable isotopes lower or equal to 600; - number of gamma energy groups lower or equal to 20