Neutron and gamma-ray cross-correlation measurements of MOX fuel using liquid scintillators

The detection of special nuclear material (SNM) is a very difficult problem: typically, the signals are weak thus difficult to distinguish from the background and in many practical applications additional shielding can be expected. In order to detect SNM more accurately, new methods to isolate the source signal are needed. Using cross-correlation functions it may be possible to identify the time-correlated particles from fission events above the background. To examine this feasibility, measurements were performed on 1-kg MOX fuel samples, a ²⁵²Cf source, and an AmBe source. Using pulse shape discrimination the particle types were isolated and the individual correlation contributions were determined. By comparing the (n, n) peak of the correlation curves a distinct difference is observed between a spontaneous fission source and an (α, n) source.