Enhancement in gamma-ray induced decomposition of sodium and potassium nitrates by borate and cyanide additives

Abstract

Gamma radiolytic decomposition of sodium and potassium nitrates and its admixtures with respective cyanide and borate additives has been studied over a wide absorbed dose range from 675 to 500 kGy. The decomposition of nitrate increases with the nature and concentration of the additive in the admixture. The enhancement is more significant at >80 mol% of the additive. G(NO2) values, calculated on the basis of electron fraction of the nitrate salt, decrease with increasing concentration of the nitrate. ESR spectral studies suggest the formation of radical species such as BO 4 and B(~ 3 etc. in borates whereas in case of cyanide additive F H centres are produced. The radical species and colour centres so produced may then transfer their energy to nitrate and cause enhancement in decomposition. A comparison with other oxyanion additives shows that G(NO2) values decrease in the order PO 3 > B4 O2 > SO 2 > CO 2 . Similarly, the nature of the cation also affects the decomposition.

Effect of cation size on the 60Co-gamma radiolytic decomposition of alkali and alkaline earth metal nitrates

“…In earlier studies on the effect of various additives such as sulphate, phosphate, carbonate, borate, oxide and halide, it has been observed that besides anion, the nature of cation also influences radiolytic behaviour (Agrawal and Garg, 1998, 1999, 2001, 2004Joshi and Garg, 1994b). In general, it has been observed that G-values are enhanced to a larger extent when a potassium salt of sulphate/carbonate/phosphate is added to NaNO 3 compared to its respective sodium salt.…”

“…It has been observed that G(NO 2 À ) values increase with the charge on outer cation and the size of cation, especially in the case of pure alkali and alkaline earth metal nitrates (Joshi and Garg, 1994a, b;Kulkarni and Garg, 1984;Agrawal and Garg, 1998). Boldyrev (1971) studied the effect of doping Tl + , Sr 2+ , Pb 2+ , Ce 3+ , La 3+ , Pr 3+ and Nd 3+ ions on the radiolytic decomposition of KNO 3 and reported that the radiation yield increased due to formation of defects in the lattice.…”

“…Gamma radiolysis of inorganic nitrates in solid state is affected by several factors including pressure, temperature, isotopic substitution and nature and size of anion (Chen and Johnson, 1962;Johnson, 1970;Parwate and Garg, 1984;Joshi and Garg, 1994a, b;Agrawal and Garg, 1998, 1999, 2001, 2004. It has been observed that G(NO 2 À ) values increase with the charge on outer cation and the size of cation, especially in the case of pure alkali and alkaline earth metal nitrates (Joshi and Garg, 1994a, b;Kulkarni and Garg, 1984;Agrawal and Garg, 1998).…”

Effect of oxide additives on radiolytic decomposition of potassium nitrate

“…5-8 Formation of NO 2-resulting from gamma radiolytic decomposition of inorganic nitrates is significantly affected by various additives such as sulfate, 6 carbonate, 8 phosphate, 8 oxide, 10 halide, 11 borate and cyanide. 12 The effect of oxide additives on X-ray and ~,-irradiated ammonium nitrate has been studied by NEVOSTRUEV and ZAKHAROV 13 and PATIL et al14 PATIL and co-workersl4-16 studied gamma radiolytic decomposition of alkali metal nitrates in the presence of different oxides and proposed energy transfer in between the surfaces. Enhancement in radiolytic decomposition has been attributed to energy transfer from the additive to the nitrate via defect centers and radical species.…”