A. Rajasingam, A.S. Hoover, M.L. Fensin, S.J. Tobin, W.S. Charlton, S. Saavedra, A.A. Stafford, D. Strohmeyer, M.T. Swinhoe, “Modeling X-ray Fluorescence from Spent Fuel Rods”, 2009 Annual Meeting of the Institute of Nuclear Materials Management, Tucson, AZ, July 12-15, 2009.
X-Ray Fluorescence (XRF) is one of thirteen non-destructive assay techniques being researched for the purpose of quantifying the Pu mass in used fuelassemblies as part of the Next Generation Safeguards Initiative. The modelingportion of this research will be conducted with the Monte Carlo N-Particle eXtended (MCNPX) transport code. The research presented here was undertaken to test the capability of MCNPX so that it can be used to benchmark measurements made at the ORNL and to give confidence in the application of MCNPX as a predictive tool of the expected capability of XRF in the context of used fuelassemblies. The benchmarking of experimental work will be presented in a future publication. The main focus of this paper is a code-to-code comparison between MCNPX and Geant4 code. Since XRF in used fuel is driven by photon emission and beta decay of fission fragments, both terms were independently researched. Simple cases and used fuel cases were modeled for both source terms. The source term for photons emitted from used fuel is well known, however, the beta term is not well known. In order to prepare for benchmarking to experiments, it was necessary to determine the significance of the various fission fragments for beta excitation of uranium and plutonium X-rays.