Plutonium Migration during the Leaching of Cemented Radioactive Waste Sludges

Show simple item record Law, Kathleen A. Parry, Stephen A. Bryan, Nicholas D. Heath, Sarah L. Heald, Steven Knight, Darrell O'Brien, Luke Fuller, Adam J. Bower, William R. Law, Gareth T. W. Livens, Francis R. 2019-06-28T10:51:01Z 2019-06-28T10:51:01Z 2019-01-08
dc.identifier.citation Law , K A , Parry , S A , Bryan , N D , Heath , S L , Heald , S , Knight , D , O'Brien , L , Fuller , A J , Bower , W R , Law , G T W & Livens , F R 2019 , ' Plutonium Migration during the Leaching of Cemented Radioactive Waste Sludges ' , Geosciences , vol. 9 , no. 1 , 31 .
dc.identifier.other PURE: 120897172
dc.identifier.other PURE UUID: 69247423-50c4-4d01-8144-d1b8f3a6d5bd
dc.identifier.other Scopus: 85060376803
dc.identifier.other WOS: 000459746300031
dc.identifier.other ORCID: /0000-0002-2320-6330/work/58958362
dc.description.abstract One of the most challenging components of the UK nuclear legacy is Magnox sludge, arising from the corrosion of Mg alloy-clad irradiated metallic U fuel that has been stored in high pH ponds. The sludges mainly comprise Mg hydroxide and carbonate phases, contaminated with fission products and actinides, including Pu. Cementation and deep geological disposal is one option for the long-term management of this material, but there is a need to understand how Pu may be leached from the waste, if it is exposed to groundwater. Here, we show that cemented Mg(OH)2 powder prepared with Pu(IV)aq is altered on contact with water to produce a visibly altered ‘leached zone’, which penetrates several hundred microns into the sample. In turn, this zone shows slow leaching of Pu, with long-term leaching rates between 1.8–4.4 × 10−5% of total Pu per day. Synchrotron micro-focus X-ray fluorescence mapping identified decreased Pu concentration within the ‘leached zone’. A comparison of micro-focus X-ray absorption spectroscopy (μ-XAS) spectra collected across both leached and unleached samples showed little variation, and indicated that Pu was present in a similar oxidation state and coordination environment. Fitting of the XANES spectra between single oxidation state standards and EXAFS modeling showed that Pu was present as a mixture of Pu(IV) and Pu(V). The change in Pu oxidation from the stock solution suggests that partial Pu oxidation occurred during sample ageing. Similarity in the XAS spectra from all samples, with different local chemistries, indicated that the Pu oxidation state was not perturbed by macro-scale variations in cement chemistry, surface oxidation, sample aging, or the leaching treatment. These experiments have demonstrated the potential for leaching of Pu from cementitious waste forms, and its underlying significance requires further investigation. en
dc.format.extent 13
dc.language.iso eng
dc.relation.ispartof Geosciences
dc.rights cc_by
dc.rights.uri info:eu-repo/semantics/openAccess
dc.subject 116 Chemical sciences
dc.subject 114 Physical sciences
dc.subject plutonium
dc.subject radioactive waste
dc.subject speciation
dc.subject cement
dc.subject leaching
dc.subject SPECIATION
dc.title Plutonium Migration during the Leaching of Cemented Radioactive Waste Sludges en
dc.type Article
dc.contributor.organization Department
dc.contributor.organization Department of Chemistry
dc.description.reviewstatus Peer reviewed
dc.relation.issn 2076-3263
dc.rights.accesslevel openAccess
dc.type.version publishedVersion

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