  A new concept for thermal neutron based correlation and multiplicity
measurements is proposed in this paper. The main idea of the concept consists
of using 2.223 MeV gammas (or 1.201 MeV, DE) originating in the
1H(n,gamma)2D-reaction instead of using traditional thermal neutron counting.
Results of investigations presented in this paper indicate that gammas from
thermal neutron capture reaction preserve the information about the correlation
characteristics of thermal (fast) neutrons in the same time scale. Therefore,
instead of thermal neutron detectors (or as a complement) one may use
traditional and inexpensive gamma detectors, such NaI, BGO, CdZnTe or any other
gamma detectors. In this work we used D8x8 cm2 NaI scintillator to test the
concept. Thus, the new approach helps to address the problem of replacement of
3He-counters and problems related to the specific measurements of spent nuclear
fuel directly in the spent fuel pool. It has a particular importance for
nuclear safeguards and security. Overall, this work represents the proof of
concept study and reports on the experimental and numerical evidence that
thermal neutron capture gammas may be used in the context of correlation and
multiplicity measurements. Investigations were performed for a 252Cf-correlated
neutron source and an 241Am-Be-random neutron source. The related idea of Gamma
Differential Die-Away approach is investigated numerically in this paper as
well, and will be tested experimentally in a future work.
