Characterization of select physical and thermal properties of crystalline 97% 10B powder

Abstract

A thermal+epithermal neutron irradiation canister was constructed at the University of Texas at Austin’s TRIGA Mark-II reactor to create an irradiation facility with a fast neutron energy spectrum resembling the Watt fission spectrum. The irradiation canister primarily used 97% enriched 10B powder wrapped in a 0.5 mm layer of Cd. This work details a follow-up on the heating studies of the facility where the boron powder involved did not have a well documented thermal conductivity measurement existing in literature. Two experiments using the radial heat flow methodology were performed to measure the effective thermal conductivity of the irradiation canister and consequentially the boron powder. An outside experiment performed by Hot Disk® was used to affirm the results of the radial heat flow method. Hot Disk® reported the thermal conductivity to be 0.2255 ±0.0012WmK at 23 °C. Extrapolations of a powder-bed approximation concluded the agreement between the radial heat flow method data and the Hot Disk® data. SolidWorks Flow simulations were performed to determine the heating in the irradiation canister at a reactor power level of 950 kW. The heating in the irradiation canister was modeled using MCNP6.1.1beta +F6 tallies. SEM, XRD, FTIR and TOF-SIMS were performed to characterize the powder’s morphology, structure and isotopic composition. Boric acid was found to comprise about 2% of the mass content of the air-exposed powder samples.