Simulation of Nuclear Resonance Fluoresence for the Quantification of Plutonium-239 in Spent Nuclear Fuel

Abstract:

There is a need for a technique that is able to timely and accurately quantify the amount of plutonium-239 in spent nuclear fuel. With the recent developments of mono-energetic gamma-ray systems it is possible to use Nuclear Resonance Fluorescence for this task. Previous gamma-ray sources for the technique were Bremsstrahlung sources. There was a distinct disadvantage with this technique due to the broad energy spectrum that Bremsstrahlung sources create. However, at Lawrence Livermore National Laboratory a new source has been developed with uses Compton scattering of photons off of electrons to create extremely thing energy bandwidth gamma-rays. In this project a Monte Carlo code developed by Lawrence Livermore National Laboratory, known as COG, was used to investigate detector designs for use with mono-energetic gamma-ray sources to quantify plutonium in spent nuclear fuel assemblies in this research. It is shown that the technique is viable for the quantification of plutonium in fresh and spent mixed oxide fuel. Due to an unexplainable flattening of the number of Nuclear Resonance Fluorescence for low plutonium-239 concentrations, <1% atom percent, it is not clear if the technique will work for spent nuclear fuel. Investigation into the cause of this flattening was conducted; however, a concrete explanation of the flattening could not be found. A more in depth analysis of COG's capabilities must be conducted to determine what is causing this anomaly.