ESTIMATION OF TIME CONSTANT IN ACCOUNTING FOR DELAED NEUTRONS

D. G. Modestov
VANT. Ser.: Mat. Mod. Fiz. Proc 2022. Вып.1. С. 17-26.

      The difference between the time constant calculation techniques for the neutron transport problem and similar techniques for arbitrary particles is small. The specific feature is in accounting for delayed neutrons, which is usually performed with the approximation, in which the transport of predecessor nuclei is considered in its simplified form. For this case, the paper presents the transport process simulation technique with such approximation. Asymptotic dependences of the bias error were obtained for it. It is shown, in particular, that for subcritical systems the behavior of such error is the same as in the method of generations used to solve a conditionally critical problem, while for supercritical systems it makes no contribution. To demonstrate the technique capabilities, the paper presents results of the time constant calculation for two systems: an all-metal critical assembly and a VVER-1000 nuclear reactor. Both subcritical and supercritical states were considered. Calculations were carried out with and without consideration of delayed neutrons. Results of these calculations confirm the asymptotic behavior of error and correctness of the proposed technique, if results are compared with those for an unsteady problem.