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The Steady-state Approach: A Model Describing the Dynamics of Spent Nuclear Fuel Dissolution in Groundwater
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2007. , v, 42 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2007:20
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4336ISBN: 978-91-7178-631-9 (print)OAI: oai:DiVA.org:kth-4336DiVA: diva2:11859
Public defence
2007-04-27, K1, KTH, Teknikringen 56, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

Qc 20170222

Available from: 2007-04-17 Created: 2007-04-17 Last updated: 2017-02-22Bibliographically approved
List of papers
1. Geometrical alpha- and beta-dose distributions and production rates of radiolysis products in water in contact with spent nuclear fuel
Open this publication in new window or tab >>Geometrical alpha- and beta-dose distributions and production rates of radiolysis products in water in contact with spent nuclear fuel
2006 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 359, no 02-jan, 1-7 p.Article in journal (Refereed) Published
Abstract [en]

A mathematical model for the dose distribution and production rates of radiolysis products in water surrounding spent nuclear fuel has been developed, based on the geometrical and energetic properties of radiation. The nuclear fuel particle is divided into layers, from which the radiation emits. The water is likewise divided into layers, where the doses are distributed. The doses are stored in vectors which are added to determine the total dose rate. A complete inventory with over 200 radionuclides has been used as input data for the model. The purpose of the model is to describe the geometrical dose distribution as a function of fuel age and burn-up, to be used as input data for kinetic modeling of the fuel dissolution. The results show that the P-dose contribution close to the spent fuel surface is negligible. Also, the variation in the relative OC/P dose contribution between different ages and burn-ups is insignificant. The alpha- and beta-dose rates vary between different burn-ups of the same age; the younger the fuel is, the larger is the difference. Exponential functions have been fitted to the relations between fuel age and average dose rate, giving useful expressions for determining average dose rates for fuel ages other than those covered in this work.

Keyword
dissolution, oxidation, corrosion, uo2
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-16150 (URN)10.1016/j.jnucmat.2006.08.001 (DOI)000242317000001 ()2-s2.0-33750351933 (Scopus ID)
Note
QC 20100811Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Simulations of H2O2 concentration profiles in the water surrounding spent nuclear fuel
Open this publication in new window or tab >>Simulations of H2O2 concentration profiles in the water surrounding spent nuclear fuel
2008 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 372, no 1, 32-35 p.Article in journal (Refereed) Published
Abstract [en]

A simple mathematical model describing the hydrogen peroxide concentration profile in water surrounding a spent nuclear fuel pellet as a function of time has been developed. The water volume is divided into smaller elements, and the processes that affect hydrogen peroxide concentration are applied to each volume element. The model includes production of H2O2 from alpha-radiolysis, surface reaction between H2O2 and UO2 and diffusion. Simulations show that the surface concentration of H2O2 increases fairly rapidly and approaches the steady-state concentration. The time to reach steady-state is sufficiently short to be neglected compared to the times of interest when simulating spent fuel dissolution under deep repository conditions. Consequently, the steady-state approach can be used to estimate the rate for radiation-induced spent nuclear fuel dissolution.

Keyword
Computer simulation; Concentration (process); Function evaluation; Nuclear fuels; Nuclear fuel dissolution; Steady-state concentration; Hydrogen peroxide
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-17329 (URN)10.1016/j.jnucmat.2007.01.279 (DOI)000253259700003 ()2-s2.0-36549056634 (Scopus ID)
Note
QC 20100811Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Simulations of H2O2 concentration profiles in the water surrounding spent nuclear fuel taking mixed radiation fields and bulk reactions into account
Open this publication in new window or tab >>Simulations of H2O2 concentration profiles in the water surrounding spent nuclear fuel taking mixed radiation fields and bulk reactions into account
2008 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 374, no 1-2, 281-285 p.Article in journal (Refereed) Published
Abstract [en]

To simulate the dynamics of the concentration gradient of hydrogen peroxide in groundwater surrounding spent nuclear fuel under various conditions, a model has been developed. The model treats the water volume as a sequence of volume elements, and applies the processes that affect hydrogen peroxide concentration to each volume element. The surface steady-state concentrations of H2O2, and the time. to reach steady-state, have been determined under different conditions. The processes accounted for in the model are radiolytic production of H2O2 from alpha- and beta-radiation, surface reactions consuming H2O2, homogeneous reactions consuming H2O2, and diffusion. The system has been modeled mainly for different surface reaction rate constants and homogeneous (bulk) reaction rate constants. The simulations show that the surface concentration of H2O2 approaches the steady-state concentration very rapidly and that the impact of homogeneous (bulk) reactions consuming H2O2 On the steady-state concentration is significant.

Keyword
Computer simulation; Diffusion; Groundwater; Hydrogen peroxide; Rate constants; Radiation fields; Steady-state concentration; Volume elements; Nuclear fuels
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-17408 (URN)000254413900033 ()2-s2.0-38749106122 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-06-02Bibliographically approved
4. 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
5. Simulation of radiation induced dissolution of spent nuclear fuel using the steady-state approach. A comparison to experimental data
Open this publication in new window or tab >>Simulation of radiation induced dissolution of spent nuclear fuel using the steady-state approach. A comparison to experimental data
2008 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 374, no 1-2, 286-289 p.Article in journal (Refereed) Published
Abstract [en]

Using the recently developed steady-state model for simulation of radiation induced dissolution of spent nuclear fuel in water we have estimated the rate of dissolution for relatively fresh fuel to 1.64 x 10(-9) Mol m(-2) s(-1). A series of experiments have been performed on fuel fragments in deoxygenated water containing 10 mM HCO3-. The dissolution rates obtained from these experiments range from 2.6 x 10(-10) to 1.6 x 10-9 Mol m(-2) s(-1). The leaching time in the experiments is 40 days or less and during this time the amount of released uranium increases linearly with time which indicates that the system has reached steady-state. The excellent agreement between the estimated dissolution rate and the dissolution rates obtained from the spent nuclear fuel leaching experiments indicates that the steady-state approach can indeed be used to predict the rate of spent nuclear fuel dissolution.

Keyword
Computer simulation; Dissolution; Radiation; Deoxygenated water; Dissolution rates; Fuel fragments; Steady-state model; Nuclear fuels
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-17409 (URN)10.1016/j.jnucmat.2007.08.009 (DOI)000254413900034 ()2-s2.0-38749151829 (Scopus ID)
Note
QC 20100811Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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