Long Term Plutonium Solubility and Speciation Studies in a Synthetic Brine

Nitsche, H.; Roberts, Kevin E.; Xi, Ruihua; Prussin, T.; Becraft, Kevin A.; Mahamid, I. Al; Silber, Herbert B.; Carpenter, Scott A.; Gatti, R.C.; Novak, Craig F.

doi:10.1524/ract.1994.6667.s1.3

Cited by 6 publications

(7 citation statements)

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“…The studies by Yamaguchi et al, 14 Nitsche et al, 19 and Choppin, 20 suggest that Pu(IV) in neutral or alkaline aqueous solutions requires a long time, in the range of weeks to years, depending on the system, to attain thermodynamic equilibrium. By contrast, residence times in the pond effluent treatment processes are short (of the order of a few minutes).…”

Section: Discussionmentioning

confidence: 99%

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Plutonium behaviour in nuclear fuel storage pond effluents

Parry

O’Brien

Fellerman

et al. 2011

Energy Environ. Sci.

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Corrosion of the cladding of spent Magnox nuclear fuel elements in water-filled storage ponds has produced a settled layer of fine particulate sludge (corroded Magnox sludge; CMS). CMS is believed to be predominantly composed of brucite (Mg(OH) 2 ), and is contaminated with fragments of spent fuel, together with the associated Pu and fission products. For safe management of the ponds and eventual removal of the sludge as part of pond decommissioning, a comprehensive understanding of sludge chemistry is required. Brucite can sequester Pu from solution and, given that brucite can also form colloidal species in solution, this interaction may enhance Pu mobility within the ponds. To assess the likely effect on Pu mobility, we have measured the affinity of 'dissolved' 239 Pu for a CMS simulant using a series of ultrafiltration experiments. The experiments were performed using a model Magnox storage pond liquor containing Pu, a CMS simulant, sodium carbonate, polyelectrolyte, and silica. Solution pH was controlled by the addition of sodium hydroxide, perchloric acid, and carbon dioxide gas to mimic storage pond and effluent treatment plant conditions. Multivariate analysis of the results was used to identify which parameters influenced Pu filterability. The presence of carbonate ions (0.03 M) had the largest effect on the system, allowing the majority of Pu to pass the filter. Addition of polyelectrolyte (0.35 ppm) produced a significant increase in Pu retention, even in the presence of carbonate and absence of CMS. The presence of CMS, even at only 3 ppm, increased Pu filterability, which was enhanced at higher pH. Over the pH range 7-11, Pu was generally better retained at higher pH. A 3-way interaction (the presence of CMS and polyelectrolyte at pH 11) affecting Pu filterability was also identified. The presence of silica (at 1 ppm) in the model system did not influence Pu filterability. Additional filtration experiments indicated a strong positive correlation between CMS concentration and Pu filter retention. This interaction was pH dependent, with more Pu filtered at pH 11.5 than at pH 10.8. Increased Pu filtration at high pH may reflect an increase in negatively charged surface species on the CMS particulate, and increased sorption of Pu although the precipitation of more CMS particulate at higher pH could also contribute. The pH dependence of Pu association with brucite is potentially an important control of Pu mobility within storage pond systems. The exact composition of the authentic pond sludge is unknown although it probably comprises mainly brucite, with smaller amounts of hydrous magnesium carbonate. Characterisation of the CMS simulant, synthesised from inactive Magnox swarf, showed the particulate to be primarily composed of platy brucite crystals, with a smaller but significant quantity of acicular artinite crystals.

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Section: Discussionmentioning

confidence: 99%

“…Pu(IV) is easily oxidised (e.g. Nitsche et al 19 ) and Pu oxidation state cannot be controlled in the experiments, so it is possible that changes in Pu solubility reflect However, this is immaterial since the experiments are aimed at identification of the controlling variables, rather than at the determination of Pu speciation.…”

Section: Discussionmentioning

confidence: 99%

Plutonium behaviour in nuclear fuel storage pond effluents

Parry

O’Brien

Fellerman

et al. 2011

Energy Environ. Sci.

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“…There are, however, new data on the potential for radiolytically induced oxidation of americium and by association, other multivalent actinides, which is an important issue that is outside the scope of this report because we are dealing with oxidation-state-specific solubility. Reducing anoxic conditions, such as those expected in the WIPP, will lead to a prevalence of lower oxidation states and correspondingly, a low solubility and potential for actinide mobility/release from the WIPP (Nitsche et al 1994;Runde 2000).…”

Section: Literature Background: Solubility Of Pu(iii) and Am(iii)mentioning

confidence: 99%

Actinide (III) solubility in WIPP Brine: data summary and recommendations

Borkowski¹,

Lucchini²,

Richmann³

et al. 2009

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“…Costanzo [18] observed excess reduction of Pu(V) in rather concentrated solutions which were oversaturated with respect to formation of Pu(IV) hydrous oxide and most likely contained Pu(IV) polymers or colloids. Strong deviations of steady state distributions from the expected equilibria were reported by Romanovski et al [19] and Nitsche et al [20] over a wide range of acidity and Pu concentration. On the other hand, acceleration of redox reactions by Pu(IV) polymers was suggested [21,22] and Newton et al [23] assumed that Pu(V) disproportionation cannot proceed at all in the absence of Pu(IV) polymers.…”

Section: Discussionmentioning

confidence: 67%