The radiolysis of nitric acid solutions was investigated using gamma, beta and alpha radiation. Solutions were gamma-irradiated under various conditions and analyzed for all stable products. Solutions that were alpha-or beta-irradiated were analyzed for nitrite ion only.Nitrite ion, the major radiolysis product, was determined as a function of nitric acid concentration. A nitrite scavenger, p-nitroaniline, was added to prevent the nitrite ion from reacting prior to analysis. The nitrite yields from alpha irradiation were appreciably lower than the yields from gamma and beta irradiations at lower acid concentrations but continually increased with increasing acid concentration. The nitrite yields from gamma or beta irradiation increased with increasing acid concentration up to about 1 M but then decreased. Similarity of the gamma and beta yields substantiated this unusual trend. Previous investigations of neutral nitrate solutions have always shown an increase in yields at the higher nitrate concentrations. A mechanism, based on L.E.T. effects on three radiolytic reactions, has been postulated to explain the differences in yields between alpha and gamma (or beta) irradiation.The radiation chemistry of the aqueous nitrate system has been the subject of much s t~d y . l -~ However, most of the investigations have been in neutral or slightly basic solutions. The only reported works in acidic solutions have been by Savel'ev et al.,5 Mahlman,6 and Vashman et al . ' Savel'ev et al., using alpha radiation, were the only investigators to analyze for all of the stable radiation products. Mahlman analyzed directly only for hydrogen and oxygen yields from gamma irradiation, and Vashman et al. examined only OH, NO2, and NO3 radical formation in alpha-irradiated frozen nitric acid solutions by electron paramagnetic resonance.One reason for the lack of information in nitric acid solutions is the difficulty of analysis of the major radiolysis products, nitrite ion and hydrogen peroxide. Nitrite ion, or HN02, not only reacts with H202 but decomposes in acid solutions. In order to prevent these reactions and obtain meaningful analytical results, an analytical reagent was added to the solutions to react with or " scavenge" the nitrite ion as it is formed. p-Nitroaniline was the reagent used although other amines have been previously used.s* The reactions of Hz02 were not prevented prior to its analysis so that H202 yields were determined only in dilute acid solutions, and are not reported here.In this study, nitric acid solutions of varying concentrations were gamma-, alpha-and beta-irradiated. Solutions that were alpha-or beta-irradiated were analyzed for nitrite only ; solutions that were gamma-irradiated were irradiated under various conditions and analyzed for all stable products. The linear energy transfer (L.E.T.) effects on the mechanism of nitrite production are discussed and the interpretations may lead to greater understanding of the radiation chemistry of the aqueous nitrate system." Nitrite " will be used in this repor...

that no ionic mechanism for the rate-determining step is indicated. The failure of stirring to alter the solution rate suggests that the process is not limited by any redox potentials existing in the immediate vicinity of the electrode.The kinetics for the initial dissolution process may be represented by the equation:where the rate constant, ho, depends only on the fading agent employed. I n the second stage the rate constant decreases with tkiickness and therefore with D -D2where h is a function of (D -D2). I t follows from Equation 1 that ho is given by the first column of Table I. Integration of Equation 2 gives:

No abstract

EXPERIMENTALReagents and Apparatus.Plutonium metal, 99.8 + % purity. Average atomic weight, 239.12. Cesium chloride, American Potash and Chemical Corp., technical grade,

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