Characterisation of plutonium species in alkaline liquors sampled from a UK legacy nuclear fuel storage pond

Combined electron microscopy and vibrational spectroscopy study of corroded Magnox sludge from a legacy spent nuclear fuel storage pond

“…The iron sulphide phase, pyrrhotite, was also found on the surface of hematite (iron oxide) particles, indicative of the actions of sulphate-reducing bacteria (SRB) within the Main Pond area, consistent with the lower redox potentials measured in these samples [12]. Many bacteria are capable of respiring on sulphate and other oxidised forms of sulphur under anaerobic conditions.…”

“…These differences, whilst somewhat unexpected, are consistent with the isolated Pond Bay having dark, quiescent conditions with a very deep sludge bed and thin overlying liquor layer compared to the Main Pond, which is purged, open to the air, has a thin sludge bed with large volume of overlying pond liquor, contains organics and is a more reducing environment. As will be seen in our accompanying paper [12], these differences extend to Pu speciation and solubility within the pond. These features are only partially replicated by simulants.…”

“…The long term ingress of CO 2 into the pond environment may also facilitate the transformation of brucite to various Mg-hydroxycarbonate phases (details given in Table S1) with differing affinities for actinide sorption [10] as well as carbonate complexation of actinide ions in solution [11]. In the course of our work [12] concentrations of Pu were measured in liquor samples from one of the legacy pond facilities at Sellafield and shown to be well above Pu solubility limits due to association with suspended or colloidal materials. Differences in oxidation states of aqueous Pu species were also observed and linked to differing pond environments.…”

Americium and plutonium association with magnesium hydroxide colloids in alkaline nuclear industry process environments

“…These wastes include large amounts of sludge that have arisen from the corrosion of spent nuclear fuel cladding as well as associated nuclear fuel storage pond liquors. It has been estimated that at Sellafield alone several thousand cubic metres of sludges containing 10 4 TBq of a-particle emitters have to be processed [1,2]. The Magnox spent fuel elements, which were used in the UK's first generation nuclear reactors, comprise a natural uranium metal core, clad by a magnesium-rich alloy.…”

Characterization of Multiple Hindered Settling Regimes in Aggregated Mineral Suspensions

“…Substantial volumes of Mg(OH) 2 rich intermediate level radioactive waste, called corroded magnox sludge (CMS), have accumulated in legacy ponds at the Sellafield nuclear decommissioning site in Cumbria, UK 35,36 . The time-line and expense of decommissioning ageing nuclear legacy buildings is highly dependent on the dewatering behaviour of Mg(OH) 2 rich suspensions, but any such spent nuclear fuel derivatives would require remote handling in a shielded hot cell for analysis.…”