A. Le Coq “Design of a Safeguards Instrument for Plutonium Quantification in an Electrochemical Refining System”, M.S. Thesis, Nuclear Engineering, Texas A&M University, College Station, TX (2013).
There has been a strong international interest in using pyroprocessing (or electrochemical refining system) to close the fast nuclear reactor fuel cycle and reprocess spent fuel efficiently. To commercialize pyroprocessing, safeguards technologies are required to be developed. In this research, the use of Self- Interrogation Neutron Resonance Densitometry (SINRD) has been investigated as a method to safeguard the process and more precisely quantify the Pu-239 content of pyroprocessing materials. This method uses a detector array with different filters to isolate the low-energy resonance in Pu-239 neutron fission crosssection. The relative response of the different detectors allows for the quantification of the amount of Pu-239 in the pyroprocessing materials.
The Monte-Carlo N-Particle (MCNP) code was used to design a SINRD instrument. This instrument is composed of a neutron source pod and a SINRD detector pod. Experimental measurements were also performed to validate the MCNP model of the instrument. Based on the results from simulations and experiments, it has been concluded that the MCNP model accurately represents the physics of the experiment. In addition, different SINRD signatures were compared to identify which of them are usable to determine the fissile isotope content. Comparison of different signatures allowed for reduction in the uncertainty of the Pu-239 mass estimate. Using these signatures, the SINRD instrumentation was shown to be able to quantify the Pu-239 content of unknown pyroprocessing materials.