CALCULATIONAL METHOD OF ONE-GROUP NUCLEAR CONSTANTS IN NUCLEAR EQUILIBRIUM STATE

The conventional one-group nuclear data sets for the nuclear equilibri um state are not consistent with the equilibrium nuclide densities, an d mar contain considerable errors. An equilibrium cell iterative calcu lation system (ECICS) has been developed to obtain the consistent neut ron spectrum, one-group constant set and nuclide number densities whic h characterize the nuclear equilibrium state. This system employs an i terative calculation scheme combining cell neutron transport calculati on and equilibrium nuclide density calculation. In ECICS, a two-step i terative method and transferred data manipulation are contrived to ens ure and accelerate the convergence. Some results obtained by ECICS are compared with the results obtained with cross section sets for fresh fuel conditions to show the efficiency of ECICS.