Calculation of neutron spectra in pebble bed reactors using different calculation methods: comparison of the calculated spectra and the mean cross sections of graphite, U-235 and Pu-240 calculated with them

Automatic translation: To account with Abbrandprogrammen, which in turn, the Basis for studies on long-term behavior of reactors, an exact knowledge of the neutron spectrum in the reactor is of great importance, because many Reactor constants, such as average effective cross sections and the diffusion coefficient, are dependent on the neutron flux profile. Since the spectrum changes due to the burning of the fissile material and the formation of fission products, which have a major influence on the effective cross sections of the various isotopes and on the reactivity of the entire core, changes over time, the neutron spectrum has to be recalculated again and again at certain time intervals. Since, on the other hand, the spectral programs require a great deal of computing time, the aim is to use methods that are as simple as possible for the calculation, although it must then be accepted that the Spectrum does not fully meet the conditions actually present in the reactor.