The long term storage of separated plutonium dioxide (PuO2) in sealed canisters requires an understanding of the processes occurring within the cans. This includes potential mechanisms that lead to can pressurisation, including the radiolysis of adsorbed water forming hydrogen. New measurements of H2production rates from three sources of PuO2 show low rates at low water monolayer coverage but a sharp increase between 75% and 95% relative humidity. This behaviour being quite different to that reported for CeO2 and UO2, which, therefore, cannot be considered as suitable analogues for PuO2/H2O radiation chemistry. It is concluded that surface recombination reactions are likely to be important in the radiation chemistry and that the H2 production arises from a radiolytic process and not a thermal reaction, at least in these experiments.
This paper was originally published in Journal of Nuclear Materials Volume 437, Issues 1–3, June 2013, Pages 359–364.
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