An easier way to a harder spectrum : generating a fast neutron flux spectrum in a Mark II TRIGA reactor using a uranium-boron-cadmium converter

Pierce, Michael T., Jr.
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The TRIGA Mark II research reactor has a flux spectrum with a predominance of thermal neutrons. While most research can be conducted using this thermal neutron flux, an exclusively fast neutron flux is preferred for some experiments, such as radiation damage studies. Although fast neutron flux spectrums are available using fast reactors or neutron generators, only a few fast reactors are currently in operation and neutron generators tend to have low fluxes. As a result, this report evaluated the possibility of generating a fast neutron flux spectrum in a thermal reactor through the use of an irradiator consisting of layers of uranium, boron, and cadmium. Simulations using Monte Carlo N-Particle Code (MCNP) determined that thin layers of these materials in an irradiator inserted into the 3-Element Facility of the UT-Austin TRIGA reactor will generate a fast neutron flux spectrum with negligible thermal flux and where over 91% of the total flux consists of neutrons with energy greater than 10 keV. Further research is recommended to calculate heat dissipation and to determine the reactivity worth of the irradiator