Characterization of Special Nuclear Material using a Time-Correlated Pulse-Height Analysis

Year
2012
Author(s)
P. Marleau - Sandia National Laboratories
P. Marleau - Sandia National Laboratories
A Enqvist - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
S. D. Clarke - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
S. A. Pozzi - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
E. Miller - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
E.C. Miller - Department of Nuclear Engineering, University of Michigan
S.A. Pozzi - Department of Nuclear Engineering, University of Michigan
J.K. Mattingly - Department of Nuclear Engineering, North Carolina State
Abstract
The ability to perform non-destructive characterization of special nuclear materials (SNM) is extremely important to ensure that nuclear material is not diverted. Cross-correlation measurements detect multiple neutrons in nanosecond time windows, which can be useful in distinguishing SNM from other neutron sources. Additionally, individual correlated particle pairings can be identified when the cross-correlation measurement is performed with liquid scintillation detectors with good pulse shape discrimination capability. Past efforts have shown that measurements utilizing the time difference between (n, n) events can be used to identify fission sources from other neutron sources. However, other correlated particle pairings can offer additional information about the source. The analysis presented here takes advantage of the timing and energy deposition of (?, n) particle pairings to further characterize the source by creating a time-correlated pulse-height (TCPH) distribution. TCPH uses the height of the detected neutron pulse along with the time difference between the correlated neutron and gamma to create a surface of the pulse height at a given time delay. For sources that do not have multiplication, the maximum possible time delay at a given pulse height can be predicted by simple kinetics. With multiplication present in the system it becomes possible to have high energy events arriving at times later than the predicted maximum. This provides a means of identifying a multiplying source from a nonmultiplying source. This work presents the initial development of this technique and preliminary measurement results from a 252Cf source compared to results simulated with MCNPX-PoliMi.