Irradiation Effects in the Storage and Disposal of Radioactive Ion-Exchange Resins

Abstract

Research Is under way to characterize the effects of selfirradiation on radwastes which may be generated when organic ion-exchange media are used in water demineralization or decontamination operations at nuclear facilities. External factors affecting the relation between laboratory evaluations and field performance are emphasized• Initial experiments do not yet indicate substantial radiation dose-rate effects on radiolytic gas yields or acid product formation, when (fully swollen) sulfonic acid resins are irradiated in a sealed air environment. At the same time, oxygen gae is removed from the environment of irradiated resins. Interaction between mild steel coupons and acidic species produced in the irradiation Induced decomposition of sulfonic acid resin results in irradiation enhanced corrosion. Corrosion rates depend on radiation dose rate, moisture content and resin chemical loading. In some caaas, corrosion rates decrease with time, suggesting depletion of acidic species within the resin bed, or a synergistic interaction between resin and corrosion coupon. Implications of these and other results on evaluating field behavior of radwsate containing ion-exchange media are discussed.

Experimental design approach for identification of the factors influencing the γ-radiolysis of ion exchange resins

“…Conversely, cation exchange resins were more stable than anion resins up to an absorbed dose of 1 MGy (Alian et al, 1984). Resins with aromatic structure or under salt forms were more gamma resistant than aliphatic ones (Swyler et al, 1983a;Nikashina et al, 1959;Dessouki et al, 1989;Mohorčič et al, 1974). The use of salt forms of resins was found to be effective in inhibiting the γ-radiation damage (Ichikawa and Hagiwara, 1973;Alian et al, 1984).…”

“…Several papers in the literature have shown that radiation damage of ion exchange resins could depend on the absorbed dose, the dose rate, and the irradiation atmosphere, and that the combination of these factors leads to different results according the nature of the resin, used pure or in mixed bed. Moreover, several studies (Pillay, 1986;Gangwer et al, 1977;Swyler et al, 1983a;Ichikawa and Hagiwara, 1973) reported that gamma irradiation at doses exceeding 0.1 MGy mainly altered the properties of ion exchange resins (principally the anion resins). Gamma rays led to direct radiolysis of these resins, resulting in the scission of functional groups and the formation of radical products, or to an indirect radiolytic effect through interactions, which could occur between the resin and its degradation products.…”

“…The irradiation stability of H þ forms increased with the degree of cross-linking of their backbone, arbitrarily defined by the percentage of divinylbenzene used in the preparation of the resin (Ichikawa and Hagiwara, 1973). Few studies have been published concerning mixed bed ion exchange resins (Swyler et al, 1983a;Baumann, 1966;Felines et al, 1995;Cau-dit-coumes, 1999); they indicate that gamma degradation of the resin remained moderate up to an absorbed dose of 1 MGy, and increased sharply at higher values.…”

“…The H 2g production yield increased with the number of methyl group on the amine (Dhiman and LaVerne, 2013). The presence of varying water content in the Amberlite matrix modified its reactivity after γ-irradiation (Swyler et al, 1983a;Kiseleva et al, 1970) and the radiation-induced degradation was more significant with the Cl À and OH À form of quaternary ammonium resin (Baidak and LaVerne, 2010). In the presence of liquid water, soluble amines such as trimethylamine (TMA aq ), dimethylamine (DMA aq ), monomethylamine (MMA aq ) and ammonium (NH þ 4aq ) have been detected in different proportions related to the type of resin and the experimental irradiation conditions (Ahmed et al, 1966;Baidak and LaVerne, 2010;Hall and Streat, 1963).…”

“…The off-gases from cation exchange resins were generally molecular hydrogen, carbon dioxide, sulfur dioxide, and traces of carbon monoxide (Pillay, 1986;Swyler et al, 1983a,b;Mohorčič et al, 1974). Several studies have demonstrated that air, oxygen and moisture accelerated decomposition of cation exchangers (Swyler et al, 1983a;Nikashina et al, 1959;Dessouki et al, 1989;Mohorčič et al, 1974;Semushin et al, 1950). The irradiation of cation resins generally involved the cleavage of -SO 3 H functional groups, the formation of free radicals and acid products.…”