Release of ⁶Li from Irradiated Beryllium-Oxide Moderator Material

The release of the reactor poison ⁶Li from irradiated BeO has been studied at 1000 to 1600°C. Release was found to be diffusion controlled, and diffusion coefficients were determined. The activation energy for diffusion was found to be 54 kcal/mole. It is tentatively proposed that ⁶Li diffuses in irradiated BeO by a cation vacancy mechanism. A large fractional release (99%) is estimated for the release of ⁶Li from BeO (corresponding to the BeO granules tested) in a reactor with a moderator temperature of 1000°C. The feasibility of reprocessing “burnt-up” BeO moderator by a high-temperature treatment was investigated and found to be promising.