Annealing reactions in potassium chromate. Part 2.—Effects of oxygen

Abstract

Isothermal and isochronal annealing of neutron-activated K₂CrO₄ were carried out in the presence and in the absence of oxygen. The ⁵¹Cr(VI)-retention is unaffected by the presence of oxygen, as previously reported. The ⁵¹Cr(III) distribution between ⁵¹Cr(III)-monomer and ⁵¹Cr(III)-dimer + polymer is insensitive to oxygen at annealing temperatures below 100°C but is affected by the presence of oxygen above 100°C. Experiments with post-irradiation-recrystallized K₂CrO₄ show a similar effect of oxygen upon the distribution of ⁵¹Cr among the ⁵¹Cr(III) species after annealing at temperatures greater than 100°C. It is proposed that crystal defects, trapped charge carriers and other species introduced by radiation do not play an essential role in the annealing reactions which occur above 100°C. Oxygen may directly affect the crystal-phase ⁵¹Cr(III)-precursor species, rather than act solely as a surface electron trap.