Oxidative dissolution of unirradiated Mimas MOX fuel (U/Pu oxides) in carbonated water under oxic and anoxic conditions

Odorowski, Mélina; Jégou, Christophe; Windt, Laurent de; Broudic, V.; Peuget, S.; Magnin, Magali; Tribet, M.; Martin, Christelle

doi:10.1016/j.jnucmat.2015.09.059

Cited by 12 publications

(8 citation statements)

References 25 publications

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“…Further leaching experiments are also being run using more complex MIMAS MOx fuel, to study the effects of a heterogeneous microstructure (UO 2 matrix including Pu--enriched agglomerates), and a higher activity due to the presence of these Pu--enriched agglomerates (Odorowski et al, 2016). The solubility limit of UO 2 •2H 2 O(am) are calculated for two different thermodynamic constants (LogK).…”

Section: [Figure 13]mentioning

confidence: 99%

Effect of metallic iron on the oxidative dissolution of UO2 doped with a radioactive alpha emitter in synthetic Callovian-Oxfordian groundwater

Odorowski

Jégou

Windt

et al. 2017

Geochimica et Cosmochimica Acta

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In the hypothesis of direct disposal of spent fuel in a geological nuclear waste repository, interactions between the fuel mainly composed of UO 2 and its environment must be understood. The dissolution rate of the UO 2 matrix, which depends on the redox conditions on the fuel surface, will have a major impact on the release of radionuclides into the environment. The reducing conditions expected for a geological disposal situation would appear to be favorable as regards the solubility and stability of the UO 2 matrix, but may be disturbed on the surface of irradiated fuel. In particular, the local redox conditions will result from a competition between the radiolysis effects of water under alpha irradiation (simultaneously producing oxidizing species like H 2 O 2, hydrogen peroxide, and reducing species like H 2, hydrogen) and those of redox active species from the environment. In particular, Fe 2+ , a strongly reducing aqueous species coming from the corrosion of the iron canister or from the host rock, could influence the dissolution of the fuel matrix. The effect of iron on the oxidative dissolution of UO 2 was thus investigated under the conditions of the French disposal site, a Callovian-Oxfordian clay formation chosen by the French National Radioactive Waste Management Agency (Andra), here tested under alpha irradiation. For this study, UO 2 fuel pellets doped with a radioactive alpha emitter (238/239 Pu) were leached in synthetic Callovian-Oxfordian groundwater (representative of the French waste disposal site groundwater) in the presence of a metallic iron foil to simulate the steel canister. The pellets had varying levels of alpha activity, in order to modulate the concentrations of species produced by water radiolysis on the surface and to simulate the activity of aged spent fuel after 50 and 10000 years of alpha radioactivity decay. The experimental data showed that whatever the sample alpha radioactivity, the presence of iron inhibits the oxidizing dissolution of UO 2 and leads to low uranium concentrations (between 4x10-10 and 4x10-9 M), through a reactional mechanism located in the very first microns of the UO 2 /water reactional interface. The mechanism involves consumption of oxidizing species, in particular of H 2 O 2 by Fe 2+ at the precise place where these species are produced, and is accompanied by the precipitation of an akaganeite-type Fe 3+ hydroxide on the surface. The higher the radioactivity of the samples, the greater the precipitation induced. Modeling has been developed, coupling chemistry with transport and based on the main reactional mechanisms identified, which enables accurate reproduction of the mineralogy of the system under study, giving the nature of the phases under observation as well as the location of their precipitation.

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Section: [Figure 13]mentioning

confidence: 99%

Effect of metallic iron on the oxidative dissolution of UO2 doped with a radioactive alpha emitter in synthetic Callovian-Oxfordian groundwater

Odorowski

Jégou

Windt

et al. 2017

Geochimica et Cosmochimica Acta

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“…Last but not least, the analogy of behavior between these (U,Ce) O 2 model materials and (U,Pu)O 2 MOX fuels appeared reasonable and satisfying from various points of view. Firstly, from a chemical point of view, the oxidative dissolution decreased with the cerium content as observed for (U,Pu)O 2 MOX pellets [29][30][31] . Kerleguer et al 31 observed that the oxidative dissolution rate decreased considerably for a homogeneous U 0.73 Pu 0.27 O 2 MOX fuel under alpha radiolysis of water.…”

Section: Discussionmentioning

confidence: 78%

“…The oxidative dissolution may be affected by microstructure and plutonium content. Indeed, plutonium is reported to stabilize the fluorite structure with respect to oxidation [29][30][31] . Moreover, plutonium exhibits different oxidation states likely to affect the processes of catalytic decomposition of hydrogen peroxide 32 and the nature of the secondary phases/altered layers at the interface.…”

Section: Introductionmentioning

confidence: 99%

Oxidative dissolution of (U,Ce)O2 materials in aqueous solutions containing H2O2

et al. 2023

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Homogeneous and heterogeneous U1-xCexO2 (with 0≤ x≤ 0.25) materials were prepared via wet and dry chemistry routes, respectively before being submitted to dynamic leaching experiments. The feeding solution containing 0.20 mmol.L−1 H2O2 was kept under air and renewed to guarantee the stability of H2O2 during the experiment. Normalized alteration rates were determined from U concentration in the leachates. For homogeneous (U,Ce)O2 materials, the dissolution rate was divided by a factor of 3 when increasing the Ce content from 0.08 to 0.25. Surface characterizations revealed that studtite precipitated all over UO2 pellet surface and only on the UO2 grains of heterogeneous U0.92Ce0.08O2 samples. The behaviour of this heterogeneous material was similar to that observed for (U,Pu)O2 in the same conditions, which revealed the reliability of cerium as a plutonium analogue.

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“…Such a positive effect has already been observed for (U,Pu)O 2 MOX fuels due to the presence of Pu(IV) which also stabilizes the fluorite structure with respect to the oxidative dissolution. One explanation lies in the formation, at the extreme surface, of an amorphous plutonium hydroxide Pu(OH) 4am with low solubility [94,95]. The stabilizing effect of zirconium has yet to be clarified according to its content, but this element is also poorly soluble in solution and easily forms amorphous hydroxides and complex polynuclear species [96].…”

Section: Influence Of Fuel Debris Chemistry On Alteration Mechanismsmentioning

confidence: 99%

Ten years after the NPP accident at Fukushima : review on fuel debris behavior in contact with water

Grambow

Nitta

Shibata

et al. 2021

Journal of Nuclear Science and Technology

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Following the NPP accident, several hundred tons of heat-generating corium and fuel debris have been cooled permanently by millions of m 3 of flowing. Knowledge on the interaction with water is crucial for any decommissioning planning.Starting from knowledge on the evolutions of the accident in the three reactor cores and associated fuel debris formations and some additional isotopic and physio-chemical information on debris fragments collected in Fukushima soils, we review the temporal evolution of the chemistry and leached radionuclide contents of the cooling water, comparing measured concentration ratios of the actinides and fission products in the water to reported results of laboratory leaching studies with either spent nuclear fuel or simulated fuel debris.As for spent fuel leaching, the fractions of inventories of 134,137 Cs in the cooling water are orders of magnitude larger than that of the actinides. After more than 10 years of fuel debris/ water contact, 137 Cs release rates have decreased by about a factor of 100. The total release of actinides from the fuel debris is orders of magnitude lower than that of 134,137 Cs or of 90 Sr. This high stability makes direct disposal of fuel debris in suitable containers after decommissioning a viable option.

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Oxidative dissolution of unirradiated Mimas MOX fuel (U/Pu oxides) in carbonated water under oxic and anoxic conditions

Cited by 12 publications

References 25 publications

Effect of metallic iron on the oxidative dissolution of UO2 doped with a radioactive alpha emitter in synthetic Callovian-Oxfordian groundwater

Effect of metallic iron on the oxidative dissolution of UO2 doped with a radioactive alpha emitter in synthetic Callovian-Oxfordian groundwater

Oxidative dissolution of (U,Ce)O2 materials in aqueous solutions containing H2O2

Ten years after the NPP accident at Fukushima : review on fuel debris behavior in contact with water

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