A sub-critical wait-time experiment to validate stochastic nuclear reactor kinetics models for low neutron source Nuclear Power Plant (NPP) start-up simulations

The aim of this paper is to present a theoretical sub-critical wait-time experiment that may be used to validate stochastic nuclear reactor kinetics models which compute the neutron population probability distribution. The regulation governing many zero-power reactors prohibits super-critical nuclear reactor operation. This paper shows that a desirable wait-time probability distribution can be computed by only modifying the neutron source strength. An analytical model, which ignores the contribution of delayed neutron precursors, is presented. Additionally, a six-delayed neutron precursor group model using the Pál–Bell equations is used to investigate the relationship between the nuclear reactor system parameters and the resulting wait-time probability distribution. Finally, this paper shows that two neutron energy group models can be collapsed down to an equivalent single (one speed or mono-energetic) neutron energy group model which accurately reproduce the same wait-time probability distribution.