Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Radiation induced dissolution of model compounds for spent nuclear fuel: mechanistic understanding of oxidative dissolution and its inhibition
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This doctoral thesis is focused on radiation induced oxidative dissolution of UO2, Pd-doped UO2, SIMFUEL (as model substances for spent nuclear fuel) and UN (a possible future fuel) and inhibition of the oxidative dissolution.

H2O2 is assumed to be the most important oxidant for spent nuclear fuel dissolution under deep repository conditions. The dissolution of uranium has been studied by oxidation by added H2O2 and by gamma irradiation in the presence and absence of carbonate.

In carbonate free solutions very low amounts of uranium are dissolved from UO2 due to formation of metastudtite, UO4·2H2O on the UO2 surface which blocks the surface from further oxidation. Metastudite formation was confirmed with Raman spectroscopy.

In the presence of carbonate, the concentration of dissolved uranium increases linearly over time for UO2 and UN, due to the complex formation between carbonate and oxidized uranium.

For SIMFUEL a large fraction of H2O2 is consumed by catalytic decomposition under all conditions examined. This results in very low amounts of uranium released. Metastudtite formation was not observed on SIMFUEL.

The oxidation during gamma radiolysis shows a larger difference in dissolution rates between UO2 and UN in carbonate solutions compared to upon oxidation by added H2O2. UN was found to have a lower dissolution rate, most probably because 50 % more oxidant is needed to reach the soluble U(VI).

It was shown that the redox reactivity of UO2 appears to increase ~1.3 times, after being irradiated at doses > 40 kGy. The effect is permanent and delayed.

The presence of sulfide shows an inhibiting effect on radiation induced dissolution due to scavenging of radiolytic oxidants and reduction of U(VI).

The catalytic properties of Pd (as a model for the noble metal particles containing Mo, Ru, Tc, Pd and Rh, formed by the fission products) are examined. It was found that Pd has a catalytic effect on the reaction between H2O2 and H2 and the second order rate constant is determined to (2.1±0.1)x10-5 m s-1. The reaction between UO2 and H2O2 is catalyzed by Pd. Pd also has a catalytic effect on the reduction of U(VI) by H2 both in aqueous solution, rate constant (1.5±0.1)x10-5, and in the solid phase, rate constants 4x10-7 m s-1 and 7x10-6 m s-1 for pellets with 1 and 3 % Pd respectively. These values are very close to the diffusion limit for these systems. The catalytic effect was not influenced by the presence of sulfide. The catalytic effect in the solid phase reduction shows that the expected conditions in a deep repository, 40 bar H2 and 1 % noble metal particle content, is sufficient to stop the dissolution.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 67 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:30
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-95433ISBN: 978-91-7501-381-1 OAI: oai:DiVA.org:kth-95433DiVA: diva2:528306
Public defence
2012-06-15, K2, Teknikringen 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120530Available from: 2012-05-30 Created: 2012-05-24 Last updated: 2012-07-06Bibliographically approved
List of papers
1. Radiation enhanced reactivity of UO2
Open this publication in new window or tab >>Radiation enhanced reactivity of UO2
2006 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 354, no 1-3, 131-136 p.Article in journal (Refereed) Published
Abstract [en]

Pure UO2 is often used as a model compound when studying reactions of importance in a future deep repository for spent nuclear fuel. The reactivity of pure UO2 is not expected to be identical to the reactivity of the UO2-matrix of spent nuclear fuel for several reasons. One reason is that the spent fuel, due to the content of radionuclides, is continuously being self-irradiated. The aim of this study is to investigate how irradiation of solid UO2 surfaces affects their reactivity towards oxidants. The effect of irradiation (gamma or electrons) on the reaction between solid UO2 and MnO4- in aqueous solutions containing carbonate has been studied. It was found that irradiation with high doses (> 40 kGy) increased the reactivity of the UO2 to about 1.3 times the reactivity of unirradiated UO2.

Keyword
Carbonates, Electron irradiation, Manganese compounds, Mathematical models, Nuclear fuels, Radioisotopes, F0700, U0200, W0200
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-8387 (URN)10.1016/j.jnucmat.2006.03.011 (DOI)000239109300011 ()2-s2.0-33745422542 (Scopus ID)
Note
QC 20100908Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2012-05-30Bibliographically approved
2. Radiation induced spent nuclear fuel dissolution under deep repository conditions
Open this publication in new window or tab >>Radiation induced spent nuclear fuel dissolution under deep repository conditions
Show others...
2007 (English)In: Environmental Science and Technology, ISSN 0013-936X, Vol. 41, no 20, 7087-7093 p.Article in journal (Refereed) Published
Abstract [en]

The dynamics of spent nuclear fuel dissolution in groundwater is an important part of the safety assessment of a deep geological repository for high level nuclear waste. In this paper we discuss the most important elementary processes and parameters involved in radiation induced oxidative dissolution of spent nuclear fuel. Based on these processes, we also present a new approach for simulation of spent nuclear fuel dissolution under deep repository conditions. This approach accounts for the effects of fuel age, burn up, noble metal nanoparticle contents, aqueous H-2 and HCO3- concentration, water chemistry, and combinations thereof. The results clearly indicate that solutes consuming H2O2 and combined effects of noble metal nanoparticles and H-2 have significant impact on the rate of spent nuclear fuel dissolution. Using data from the two possible repository sites in Sweden, we have employed the new approach to estimate the maximum rate of spent nuclear fuel dissolution. This estimate indicates that H-2 produced from radiolysis of groundwater alone will be sufficient to inhibit the dissolution, completely for spent nuclear fuel older than 100 years.

Keyword
Computer simulation, Concentration (process), Dissolution, Groundwater, Nanoparticles, Nuclear fuels, Radiation, Radioactive wastes, Radiolysis, Noble metal, Nuclear fuel dissolution, Water pollution, bicarbonate, ground water, hydrogen peroxide, metal, nanoparticle, nuclear fuel, water, Computer simulation, Concentration (process), Dissolution, Groundwater, Nanoparticles, Nuclear fuels, Radiation, Radioactive wastes, Radiolysis, Water pollution, assessment method, concentration (composition), dissolution, fuel, groundwater, oxidation, radioactive waste, repository, safety, water chemistry, article, concentration response, dissolution, oxidation, radiation, radioactive waste processing, radiolysis, Sweden
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-8390 (URN)10.1021/es070832y (DOI)000250110800036 ()2-s2.0-35348828672 (Scopus ID)
Note
QC 20100811Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2012-05-30Bibliographically approved
3. On the catalytic effects of UO2(s) and Pd(s) on the reaction between H2O2 and H-2 in aqueous solution
Open this publication in new window or tab >>On the catalytic effects of UO2(s) and Pd(s) on the reaction between H2O2 and H-2 in aqueous solution
2008 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 372, no 2-3, 160-163 p.Article in journal (Refereed) Published
Abstract [en]

The possible catalytic effects of UO2 and Pd (as a model for noble metal particles) on the reaction between H2O2 and H2 have been studied experimentally. The experiments were performed in aqueous solution using an autoclave. The aqueous solutions were pressurized with H2 or N2 and the H2O2 concentration was measured as a function of time. The experiments clearly showed that Pd catalyzes the reaction between H2O2 and H2 while UO2 has no catalytic effect. The rate constant of the reaction between H2O2 and H2 catalyzed by Pd was found to be close to diffusion controlled and independent of the H2 pressure in the range 1-40 bar. The impact of the catalytic effect on the reaction between H2O2 and H2 on spent nuclear fuel dissolution is, however, fairly small. Other possible effects of noble metal particles are also discussed, e.g. reduction of U(VI) to U(IV) in the liquid and solid phase.

Keyword
Catalyst activity, Concentration (process), Hydrogen peroxide, Palladium, Pressurization, Reaction kinetics, Solutions
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-8388 (URN)10.1016/j.jnucmat.2007.03.040 (DOI)000253180400003 ()2-s2.0-37249074552 (Scopus ID)
Note
QC 20100924Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2012-05-30Bibliographically approved
4. On the catalytic effect of Pd(s) on the reduction of UO22+ with H-2 in aqueous solution
Open this publication in new window or tab >>On the catalytic effect of Pd(s) on the reduction of UO22+ with H-2 in aqueous solution
2008 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 374, no 1-2, 290-292 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic effect of Pd(s) (as a model for noble metal particles) on the reduction of UO22+ by H-2 has been studied experimentally. The experiments were performed in aqueous solution in an autoclave. The aqueous solutions were pressurized with H-2 or N-2 and the UO22+ concentration was measured as a function of time. The experiments clearly show that Pd catalyzes the reaction between UO22+ and H-2. The rate constant of the reaction was found to be close to diffusion controlled and independent of the H-2 pressure in the range 1.5-40 bar. The effect of a catalyzed reduction of U(VI) to U(IV) in the solid phase is also discussed.

Keyword
OXIDATION; URANIUM; FUEL
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-8389 (URN)10.1016/j.jnucmat.2007.08.010 (DOI)000254413900035 ()2-s2.0-38749145101 (Scopus ID)
Note
QC 20100621Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2012-05-30Bibliographically approved
5. On the effects of fission product noble metal inclusions on the kinetics of radiation induced dissolution of spent nuclear fuel
Open this publication in new window or tab >>On the effects of fission product noble metal inclusions on the kinetics of radiation induced dissolution of spent nuclear fuel
2008 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 378, no 1, 55-59 p.Article in journal (Refereed) Published
Abstract [en]

Radiation induced oxidative dissolution of UO2 is a key process for the safety assessment of future geological repositories for spent nuclear fuel. This process is expected to govern the rate of radionuclide release to the biosphere. In this work, we have studied the catalytic effects of fission product noble metal inclusions on the kinetics of radiation induced dissolution of spent nuclear fuel. The experimental studies were performed using UO2 pellets containing 0%, 0.1%, 1% and 3% Pd as a model for spent nuclear fuel. H2O2 was used as a model for radiolytical oxidants (previous studies have shown that H2O2 is the most important oxidant in such systems). The pellets were immersed in aqueous solution containing H2O2 and HCO3- and the consumption of H2O2 and the dissolution of uranium were analyzed as a function of H2 pressure (0-40 bar). The noble metal inclusions were found to catalyze oxidation of UO2 as well as reduction of surface bound oxidized UO2 by H2. In both cases the rate of the process increases with increasing Pd content. The reduction process was found to be close to diffusion controlled. This process can fully account for the inhibiting effect of H2 observed in several studies on spent nuclear fuel dissolution.

Keyword
Fission products, Metals, Nuclear fuels, Precious metals, Radiation, Radiation effects
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-8391 (URN)10.1016/j.jnucmat.2008.04.018 (DOI)000258553500010 ()2-s2.0-47549110547 (Scopus ID)
Note
QC 20100924. Uppdaterad från Submitted till Published (20100924).Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2012-05-30Bibliographically approved
6. H2O2 and radiation induced dissolution of UO2 and SIMFUEL pellets
Open this publication in new window or tab >>H2O2 and radiation induced dissolution of UO2 and SIMFUEL pellets
2011 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 410, no 1-3, 89-93 p.Article in journal (Refereed) Published
Abstract [en]

Dissolution of the UO2 matrix is of major importance in the safety assessment of a future deep repository for spent nuclear fuel. The aim of this work is to elucidate if the observed differences in dissolution rates between SIMFUEL and UO2 can be attributed to differences in oxidant reactivity towards these two materials. To elucidate this, the oxidative dissolution of U(VI) and consumption of H2O2 have been studied for UO2 and SIMFUEL pellets under N-2 and H-2 atmosphere. The H2O2 and U(VI) concentrations have been measured as a function of reaction time. In addition, gamma-radiation induced dissolution UO2 and SIMFUEL pellets have been studied. The experiments show that while the reactivity of the two types of pellets towards H2O2 is almost identical and in good agreement with the previously determined rate constant for the reaction, the dissolution rates differ considerably. The significantly lower rate of dissolution of the SIMFUEL pellet is attributed to an increased fraction of catalytic decomposition of H2O2. The radiation chemical experiments reveal a similar but less pronounced difference between the two types of pellets. This implies that the relative impact of the radiolytic oxidants in radiation induced UO2 dissolution differs between a pure UO2 pellet and SIMFUEL

National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-32228 (URN)10.1016/j.jnucmat.2011.01.020 (DOI)000288722400012 ()2-s2.0-79951811165 (Scopus ID)
Note
QC 20110601Available from: 2011-06-01 Created: 2011-04-11 Last updated: 2017-12-11Bibliographically approved
7. H2O2 and radiation induced dissolution of UO2 and SIMFUEL in HCO3- deficient aqueous solution
Open this publication in new window or tab >>H2O2 and radiation induced dissolution of UO2 and SIMFUEL in HCO3- deficient aqueous solution
2013 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 443, no 1-3, 291-297 p.Article in journal (Refereed) Published
Abstract [en]

Understanding UO2 matrix dissolution is of major importance for the safety assessment of a future deep geological repository. Oxidative dissolution of UO2 and SIMFUEL pellets have been extensively studied in HCO3- solutions, while less is known about systems with no or very low HCO3- concentrations. The aim of this work is to elucidate the oxidative dissolution of UO2 and SIMFUEL pellets in HCO3- free solutions by studying the dissolution of U (VI) and consumption of H2O2 over time. The results are compared with previous experiments performed in HCO3- solutions. The oxidative dissolution rate is higher for the UO2 pellet in HCO3- compared to the other systems. It is evident that the kinetics of the reaction with H2O2 is qualitatively different for SIMFUEL in comparison with pure UO2. For the UO2 pellet in pure water, the presence of a secondary phase (meta) studtite, on the surface of the pellet is confirmed by Raman spectroscopy. The kinetic impact of the secondary phase is evaluated in separate UO2 powder experiments. The (meta) studtite (surface) precipitation leads to a slower release of uranium into the solution. Numerical simulations using experimentally determined rate constants are used to evaluate a simple mechanism of surface precipitation. The numerical results are in fair agreement with the experimental observations given certain criteria. In addition, the γ-radiation induced dissolution of UO 2 and SIMFUEL pellets were investigated in pure water, and compared with HCO3- systems. Also here the dissolution rate of uranium is higher for UO2 in HCO3- compared to pure water, while for SIMFUEL longer irradiation times are needed to observe any difference between pure and HCO3- containing water.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
Deep geological repository, Matrix dissolutions, Numerical results, Oxidative dissolution, Powder experiment, Radiation-induced, Safety assessments, Surface precipitation
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-95825 (URN)10.1016/j.jnucmat.2013.07.025 (DOI)000327905800040 ()2-s2.0-84882789875 (Scopus ID)
Funder
Swedish Radiation Safety Authority
Note

QC 20131115. Updated from manuscript to article in journal.

Available from: 2012-05-30 Created: 2012-05-30 Last updated: 2017-12-07Bibliographically approved
8. H2O2 and radiation induced dissolution of a UN pellet in aqueous solution: a comparison with UO2 and SIMFUEL pellets
Open this publication in new window or tab >>H2O2 and radiation induced dissolution of a UN pellet in aqueous solution: a comparison with UO2 and SIMFUEL pellets
2011 (English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-95827 (URN)
Note
QS 2012Available from: 2012-05-30 Created: 2012-05-30 Last updated: 2012-05-30Bibliographically approved
9. Inhibition of radiation induced dissolution of UO2 by sulfide: a comparision with the hydrogen effect
Open this publication in new window or tab >>Inhibition of radiation induced dissolution of UO2 by sulfide: a comparision with the hydrogen effect
2011 (English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-95828 (URN)
Note

QS 2012

Available from: 2012-05-30 Created: 2012-05-30 Last updated: 2012-11-09Bibliographically approved

Open Access in DiVA

fulltext(1440 kB)655 downloads
File information
File name FULLTEXT01.pdfFile size 1440 kBChecksum SHA-512
62ac53532326204b4448541fe714c8084b90ff4797b966a6a75e14123d1c2e47f49b2baef669ea0b8a014e5b739b3947fed198b6d17dc07239642bd50479e74d
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Nilsson, Sara
By organisation
Nuclear Chemistry (closed 20110630)
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 655 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 570 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf