A.M. LaFleur, W.S. Charlton, H.O. Menlove, M. Swinhoe, “Nondestructive Measurements of Fissile Material Using Self-Indication Neutron Resonance Absorption Densitometry (SINRAD)”, 8th International Conference on Facility Operations – Safeguards Interface, Portland, OR, March 30 – April 4, 2008.
The use of self-indication neutron resonance absorption densitometry (SINRAD) to nondestructively measure the concentration of fissile material was investigated using Monte Carlo N-Particle eXtended transport code (MCNPX) and results were benchmarked against experimental data from 1968 and 1969. This technique utilizes the unique resonance structure in the fission cross-section of different fissile isotopes by passing a neutron beam through an absorber filter, fissile sample, and then to a set of fission chambers. The sensitivity of this technique is based on using the same fissile materials in the sample and fission chamber because the effect of the resonance absorption lines in the transmitted flux is amplified by the corresponding (n,f) reaction peaks in the fission chamber. The simulated 1968 experiment consisted of modeling fissile metal plates of 235U and 239Pu with thicknesses ranging from 0.254 to 3.05 mm. The simulated 1969 experiment consisted of modeling a MOX fuel rod containing pellets of different Pu enrichments ranging from 12 % Pu to 27% Pu. The agreement of MCNPX results with results from 1968 and 1969 experimental measurements confirms the accuracy of the MCNPX models used. Future work includes the use of the SINRAD to measure the 235U and 239Pu content in LWR spent fuel and pyroprocessing materials.