Simulation of fast-reactor spectra

To simulate fast-reactor spectra, a simple shape function f(u; um , B) with spectral parameters um and B has been derived by expanding the gross shape of the spectrum into a series of Hermite functions. The parameters are determined by the moment method. It is shown through some sample problems that the shape function is applicable to both core and blanket. The value of B=0.1 is recommended for core spectra and B=0.0 for blanket spectra. Spectral simulation with this shape function is applied to studies on the burn-up reactivity and the fission-to-(n, 2 n) ratio of 232Th and 238U.