Radiolytic Production of Fluorine Gas from MSR Relevant Fluoride Salts

Radiolytic fluorine gas production at temperatures of 40°C to 60°C was investigated for the fluoride salts LiF, BeF₂, UF₄, ThF₄, and 71.7LiF-16BeF₂-12.3UF₄ (FliBe-UF₄) by gamma irradiation of powdered samples using spent fuel elements from the High Flux Reactor (HFR) Petten as the irradiation source; work of a similar nature was previously performed at Oak Ridge National Laboratory in the period 1965 to 1995. Gamma irradiation was conducted for just over 41 days, with total absorbed gamma dose ranging from ~45 MGy for the lightest salts to ~170 MGy for ThF₄ and UF₄. By measuring the gas pressure within salt-filled capsules during irradiation, it was possible to quantify radiolytic gas production for all salt samples except UF₄. Production rates are reported as the salt G-values, measured as number of fluorine molecules produced per 100 eV of energy absorbed (molecules F₂/100 eV). The G-values of the salts were found to be G(LiF) ~0.004, G(BeF₂) ~0.009, G(ThF₄) ~0.021, and G(FLiBe-UF₄) ~0.005.