Design and testing of a 10B4C capsule for spectral-tailoring in mixed-spectrum reactors

A boron carbide capsule highly enriched in 10B has been designed and used for spectral-tailoring experiments at the TRIGA reactor at Washington State University. New experiments show that enriching the boron to 96% B-10 results in additional absorption of neutrons in the resonance region thereby producing a neutron spectrum that is much closer to a pure 235U fission spectrum than measured previously with a natural boron carbide capsule. A cadmium outer cover was used to reduce thermal alpha heating. The neutron spectrum calculated with MCNP was found to be in very good agreement with measured activation rates from neutron fluence monitors.