Feynman-Y function for a subcritical assembly with intrinsic spontaneous fissions driven by external pulsed sources

Stochastic neutron transport theory is applied to the derivation of the Feynman-Y function for subcritical assemblies when external pulsed sources are used. We obtain a general relationship between the probability generating functions of the kernel and the source considering the contribution to the detector statistics of both the pulsed source and the intrinsic neutron source. An expansion in α-eigenvalues is derived for the final solution, which permits to take into account the effect of higher harmonics in subcritical systems. In addition, numerical calculations have been done for a proposed model problem to understand the applicability of the method studied.