Outgassing from alpha particle irradiation of lithium hydride and lithium hydroxide

We have experimentally studied the effects of α-particle radiation on isotopically enriched lithium hydride (⁶LiH) and its corrosion product lithium hydroxide (⁶LiOH) to determine, in particular, the type and amount of gases evolved during irradiation. SRIM Monte Carlo simulations suggest that irradiating these materials with 2.2-MeV α-particles will ionize atoms and form hydrogen vacancies in the target material, and that these α-particles will penetrate 13.5 and 9 μm into LiH and LiOH, respectively. Using an accelerator to irradiate LiH and LiOH with 2.2-MeV α-particles released only H₂ and CO₂; no other product gases were observed. At 25 °C, doses that simulated 66.5 years of actinide exposure (with accelerated fluxes) produced 2.3 × 10 ⁵ mol/(cm³ J) H₂ in LiH and 2.3 × 10 ⁶ mol/(cm³ J) H₂ in LiOH, in the form of a ∼9-μm-thick surface layer on LiH. More H₂ evolved from LiOH than from LiH. We argue that the production of H₂ gas was the result of radiolysis, rather than radiation-induced chemical reaction.