Spent Nuclear Fuel Self-Induced X-ray Fluorescence Simulations for North Anna and TMI

The challenge of accurately quantifying the plutonium content in spent nuclear fuel through pasive methods at reprocessing facilities has been a continuing dilema. A recent promising technique being developed is the measurement of self-induced x-ray fluorescence (XRF) by uranium andplutonium in spent nuclear fuel. XRF measurements were performed on North Anna and Three-Mile-Island-1 (TMI-1) fuel rod segments in a hot cell at the Coupled-End-To-End (CETE) dmonstration facility at Oak Ridge National Laboratory. In order to verift the plutonium and uranium x-ray measurement results, simulations of the fuel and detector configurations were conducted using TransLAT (a 3-D nuclear fuel depletion software system), Origen2 and MCNP. As an initial step, TransLAT simlations wereconducted to determine the radial distribution of materials and activities in the spent fuel rod s a function of fuel burn-ip. The uranium to plutonium activity ratios were then translated to source strength for the plutonium and uranium x-rays via Origen2 simulations. These simulations established a radial activity bias for each fuel case, which were considered during MCNP analysis. The MCNP simulations were used to predict detector pulse height spectra for the North Anna and TMI measurements at ORNL. Result showed good agreement between the simulated and experimental data.