On the applicability of the pulsing Feynman-α method: Validation with MUSE experiments

We investigate the application of the Feynman-α method using an external pulsed source as a subcriticality level monitoring technique. The influence of the non-Poissonian nature of the pulsed source and the presence of the intrinsic spontaneous fission source are considered. Experimental data gathered during the MUSE-4 European project for different nuclear assembly conditions are reported and applied to fit the system prompt neutron time constant within the fundamental mode approach, 1/(−α0), with theoretical expressions previously obtained. Experiments show that, under certain circumstances, the deterministic character of the external pulsed source makes the system to behave as a sub-Poissonian one. In addition, the stochastic pulsing method seems to be more adequate than the deterministic one because the number of fitting parameters is lower, and also due to its better statistical behaviour for the given experimental conditions.