The development of non-destructive assay (NDA) capabilities to directly measure the fissile content in spent fuel is needed to improve the timely detection of the diversion of significant quantities of fissile material. Currently, the International Atomic Energy Agency (IAEA) does not have effective NDA methods to verify spent fuel and recover continuity of knowledge in the event of a containment and surveillance systems failure. This issue has become increasingly critical with the worldwide expansion of nuclear power, adoption of enhanced safeguards criteria for spent fuel verification, and recent efforts by the IAEA to incorporate an integrated safeguards regime. In order to address these issues, the use of Self-Interrogation Neutron Resonance Densitometry (SINRD) has been developed to improve existing nuclear safeguards and material accountability measurements. The following characteristics of SINRD were analyzed: (1) ability to measure the fissile content in Light Water Reactors (LWR) fuel assemblies and (2) sensitivity and penetrability of SINRD to the removal of fuel pins from an assembly. The Monte Carlo Neutral Particle eXtended (MCNPX) transport code was used to simulate SINRD for different geometries. Experimental measurements were also performed with SINRD and were compared to MCNPX simulations of the experiment to verify the accuracy of the MCNPX model of SINRD. Based on the results from these simulations and measurements, we have concluded that SINRD provides a number of improvements over current IAEA verification methods. These improvements include:
- SINRD provides absolute measurements of burnup independent of the operator’s declaration.iv
- SINRD is sensitive to pin removal over the entire burnup range and can verify the diversion of 6% of fuel pins within 3Ïƒ from LWR spent LEU and MOX fuel.
- SINRD is insensitive to the boron concentration and initial fuel enrichment and can therefore be used at multiple spent fuel storage facilities.
- The calibration of SINRD at one reactor facility carries over to reactor sites in different countries because it uses the ratio of fission chambers (FCs) that are not facility dependent.
- SINRD can distinguish fresh and 1-cycle spent MOX fuel from 3- and 4-cycles spent LEU fuel without using reactor burnup codes.
View of the SINRD unit internals used in experimental measurements at LANL
- A.M. LaFleur, W.S. Charlton, H.O. Menlove, M.T. Swinhoe, "Comparison of fresh fuel experimental measurements to MCNPX calculations using self-interrogation neutron resonance densitometry", Nuclear Instruments and Methods in Physics Research A, 680 (2012).
- A.M. LaFleur, "Development of Self-Interrogation Neutron Resonance Densitometry (SINRD) to Measure the Fissile Content in Nuclear Fuel", Ph.D. Dissertation, Nuclear Engineering, Texas A&M University, College Station, TX (2011).
- A. M. LaFleur, H. O. Menlove, W. S. Charlton, M. T. Swinhoe, "Use of Self-Interrogation Neutron Resonance Densitometry to Measure the Fissile Content in a BWR 9x9 Spent Fuel Assembly", 33rd ESARDA Annual Meeting: Symposium on Safeguards and Nuclear Material Management, May 16–20, 2011, Budapest, Hungary.
- A.M. LaFleur, W.S. Charlton, H.O. Menlove, M.T. Swinhoe, S.Y. Lee, S.J. Tobin, "Experimental Benchmark of MCNPX Calculations Against Self-Interrogation Neutron Resonance Densitometry (SINRD) Fresh Fuel Measurements", 51st Annual Meeting for the Institute of Nuclear Materials Management, Baltimore, Maryland, July 11-15, 2010.
- A.M. LaFleur, W.S. Charlton, H.O. Menlove, and M. Swinhoe, "Development of Self-Interrogation Neutron Resonance Densitometry (SINRD) to Measure the 235U and 239Pu Content in a PWR 17x17 Spent Fuel Assembly", Proceedings of 31st Annual Meeting of ESARDA, May 26-28, 2009, Vilnius, Lithuania.
- A.M. LaFleur, W.S. Charlton, H.O. Menlove, M. Swinhoe, "Use of Self-Interrogation Neutron Resonance Densitometry (SINRD) to Measure the Fissile Content in Nuclear Fuel", 49th Annual INMM Meeting, Nashville, TN, July 13-17, 2008.
- 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.