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The Radiolytic Hydrogen Production from TODGA and Associated Reprocessing Systems
[Thesis]. Manchester, UK: The University of Manchester; 2017.
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Abstract
Research was conducted into the radiolytic hydrogen production from the gamma radiolysis of n-dodecane and TODGA. Experiments were conducted to determine the value of G(H2) for neat n-dodecane, TODGA, and mixtures of the two. Variables investigated were the dependence of G(H2) on dose, the effect of purging with argon, and the dose rate (between 21 and 360 Gy/min). The value of G(H2) for n-dodecane was observed to be dependent on the dose, the dose rate, and exposure to the atmosphere. When the absorbed dose increased to above 5kGy, the value of G(H2) decreased. Increasing the dose rate was observed to decrease the value of G(H2). Purging n-dodecane with argon resulted in an increased value of G(H2). When neat TODGA was irradiated, purging the system with argon did not cause an effect on the yield of hydrogen. When the absorbed dose increased above 5kGy, the value of G(H2) increased; the opposite behaviour to n-dodecane. Irradiating mixtures of n-dodecane and TODGA results in a decreased yield of hydrogen when compared to extrapolations of from neat n-dodecane and TODGA. A model was constructed for hydrocarbon radiolysis, using an iterative approach to solving a set of simultaneous equations, based on the reactions of hydrocarbon radicals after radiolysis. The model did not include a mechanism for the experimentally observed dependence of G(H2) on the dose rate of the incident gamma-irradiation. In the future reprocessing system EURO-GANEX, a solution of 0.2M TODGA and 0.5M DMDOHEMA in a hydrocarbon based diluent is expected to be used as the organic extractant phase. The experimentally determined values of G(H2) for 0.2M TODGA in n-dodecane were as follows. Under aerated conditions: (0.208+-0.004)u mol/J during the LDR, (0.158+-0.003)u mol/J for absorbed doses above 5kGy; and (0.32+- 0.01)u mol/J for argon purged solutions in the LDR.