Chemical Effects of 31P(n,γ)32P Reaction in Phosphate Glass—A Radiation Chemical Approach to Hot Atom Chemistry

Abstract

Sodium metaphosphate glass, with a polymerization degree of 50–100, was used as target material for the study of the chemical effects of (n, γ) reaction. Mean oxidation number of 32P was introduced as a new parameter to elucidate the oxidation reaction brought on the recoil product. The mean oxidation number of 32P from (n, γ) recoil in such glassy polyphosphate was about +4. More than 90% of the 32P set free was reattached as an end group in the newly formed radioactive polyphosphate. The recoiled monoatomic 32P species (less than 10% of the total 32P) defficient in oxygen kept a low mean oxidation number ca. +3. Ionizing radiation produced color center (with λmax at 510 nm) which seemed partially to oxidize the 32P product. The effect was very weak, and could be suppressed by the hold scavengers. Thermal annealing showed that the mean oxidation number of 32P rapidly attained +5 (the valence of target) by 300 °C; however, it seems very difficult to raise the mean oxidation number of 32P to +5 by γ-ray annealing. The oxidation of 32P through thermal annealing is considered to be a diffusion process, with an activation energy of ca. 7×103 cal/mol. Possible reaction between the hot-zone and the radiation spurs is discussed.