Radiolytic instability of ferrous sulfamate in nuclear process solutions

The radiolytic oxidation of Fe(II) and the destruction of sulfamic acid (SA) in feed solutions for solvent extraction purification of 237Np and 238Pu from spent nuclear fuels have been investigated. Cobalt-60 gamma radiolysis of simulated solutions established that 100-eV yields for depletion of Fe(II) and SA are 13 and 5.6, respectively. Also, the normally occurring components of process solutions do not significantly affect these yields. An actual process solution was studied in which radiolysis was almost entirely from gamma-ray and beta-particle decay of 235U fission products along with a small fraction from alpha-particle decay of transuranium isotopes. In this solution, G(Fe3+) is 12, which is in good agreement with results with simulated solutions. Interpretation of the results suggests that Fe(II) not only reduces Np(V) and Pu(IV) but also protects the reduced states from reoxidation by radiolytically formed intermediates; when Fe(II) is depleted, the reduced states are immediately oxidized