Combined effects of Fe(II) and oxidizing radiolysis products on UO2 and PuO2 dissolution in a system containing solid UO2 and PuO2

Amme, M.; Pehrman, Reijo; Deutsch, R.; Roth, Olivia; Jönsson, Mats

doi:10.1016/j.jnucmat.2012.06.036

Cited by 18 publications

(9 citation statements)

References 23 publications

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“…The absence of oxidation on the surface of UO 2 under alpha irradiation in the presence of hydrogen has been demonstrated, but also a stop in the release of radionuclides from irradiated fuel. The presence of iron has been the subject of far fewer studies in the literature, particularly in the presence of a predominantly alpha irradiation field (Ödegaard--Jensen and Oversby, 2008;Amme et al, 2012). These studies agree on the fact that ferrous ions can consume oxidizing species like H 2 O 2 , potentially limit the oxidation of the UO 2 matrix and cause considerable decreases in the concentrations of uranium in solution.…”

Section: Introductionmentioning

confidence: 95%

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: Introductionmentioning

confidence: 95%

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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“…Uraninite (UO 2 ) is thermodynamically unstable under oxidizing conditions and combined with the alpha (a)-radiation eld drive oxidative dissolution. [24][25][26][27] The oxidation process is controlled by the concentration of H 2 O 2 ; where the high oxidation potential will lead to the formation of soluble UO 2(aq)…”

Section: Monitoring Bromide Effect In the Liquid Cellmentioning

confidence: 99%

Monitoring bromide effect on radiolytic yields usingin situobservations of uranyl oxide precipitation in the electron microscope

et al. 2018

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During electron microscopy observations of uranium-bearing phases and solutions in a liquid cell, the electron beam induced radiolysis causes changes in the chemistry of the system. This could be useful for investigating accelerated alteration of UO 2 and can be also used to monitor radiolytic effects. Low concentrations of bromide in aqueous solutions are known to reduce the generation rate of H 2 O 2 during radiolysis and increase H 2 production. We deduced the presence of radiolytic H 2 O 2 by monitoring the formation of a uranyl peroxide solid from both solid UO 2 and a solution of ammonium uranyl carbonate at neutral pH. Additionally, the effect of bromine on water radiolysis was investigated through chemical modelling and in situ electron microscopy. By measuring the contrast in the electron microscopy images it was possible to monitor H 2 O 2 formation and diffusion from the irradiated zone in agreement with the models.

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“…Another important redox species is Fe(0) that oxidizes easily. It counteract the oxidizing effects of radiolytic species and limit the mobility of radionuclides [125][126][127][128][129]. However, the location of the redox front [105] which spatially delimits the oxidizing and reducing zones will depend on the availability of iron through the reactivity of the available iron phases, their oxidation states (Fe(II)/Fe(III)) and the nature of the irradiation fields.…”

Section: V-3) the Role Of Electroactive Redox Speciesmentioning

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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Combined effects of Fe(II) and oxidizing radiolysis products on UO2 and PuO2 dissolution in a system containing solid UO2 and PuO2

Cited by 18 publications

References 23 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

Monitoring bromide effect on radiolytic yields usingin situobservations of uranyl oxide precipitation in the electron microscope

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

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