1
|
Wang C, Myshkin VF, Khan VA, Panamareva AN. A review of the migration of radioactive elements in clay minerals in the context of nuclear waste storage. J Radioanal Nucl Chem 2022. [DOI: 10.1007/s10967-022-08394-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
2
|
Kim S, Bender WM, Becker U. Exploring the kinetics of actinyl-EDTA reduction by ferrous iron using quantum-mechanical calculations. Phys Chem Chem Phys 2021; 23:5298-5314. [PMID: 33634290 DOI: 10.1039/d0cp05179a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reduction of An(vi) (An = U, Np, and Pu) to An(iv) significantly decreases its solubility and mobility. This reaction can be hindered by complexation with inorganic (e.g., carbonate) or organic ligands. Ethylenediaminetetraacetic acid (EDTA) is one such organic ligand that forms stable complexes with actinides. Therefore, it may enhance the mobility of actinides. However, the redox kinetics and mechanisms of actinyl (An(v/vi)O2+/2+)-EDTA are not well characterized yet and are thus studied here using quantum-mechanical calculations. The principle is to approach the actinyl-EDTA and Fe2+ (reductant) in small incremental steps and calculate the system energy at each distance. The overall reaction is then delineated into sub-processes (encounter frequency in bulk solution, formation of outer-sphere complex, transition from outer- to inner-sphere complex, and electron transfer), and reaction rates are determined for each sub-process. The formation of outer-sphere complexes occurs rapidly in microseconds to seconds over a wide range of actinyl concentrations (pM to μM); in contrast, the transition to the inner-sphere complex is relatively slow (milliseconds to a few seconds). Immediate electron transfer to form the pentavalent actinide is observed along the reaction path for Np(vi) and Pu(vi), but not for U(vi). Surprisingly, in acidic conditions, one of the carboxylic groups gets protonated in EDTA of [UO2(edta)]2- rather than one of the amino groups. This process-based series of calculations can be applied to any redox reaction and allows the prediction of changes to the rate law and rate-limiting step in a more fundamental way for different environments.
Collapse
Affiliation(s)
- Sooyeon Kim
- Department of Earth and Environmental Sciences, University of Michigan, Room 2534, North University Building, 1100 N University Ave, Ann Arbor, MI 48109-1005, USA.
| | - Will M Bender
- Department of Earth and Environmental Sciences, University of Michigan, Room 2534, North University Building, 1100 N University Ave, Ann Arbor, MI 48109-1005, USA. and Geosyntec Consultants, 1111 Broadway, 6th Floor, Oakland, CA 94607, USA
| | - Udo Becker
- Department of Earth and Environmental Sciences, University of Michigan, Room 2534, North University Building, 1100 N University Ave, Ann Arbor, MI 48109-1005, USA.
| |
Collapse
|
3
|
Sugiura Y, Tomura T, Ishidera T, Doi R, Francisco PCM, Shiwaku H, Kobayashi T, Matsumura D, Takahashi Y, Tachi Y. Sorption behavior of selenide on montmorillonite. J Radioanal Nucl Chem 2020. [DOI: 10.1007/s10967-020-07092-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
4
|
Arima T, Idemitsu K, Inagaki Y, Kawamura K, Tachi Y, Yotsuji K. Diffusion and adsorption of uranyl ion in clays: Molecular dynamics study. PROGRESS IN NUCLEAR ENERGY 2016. [DOI: 10.1016/j.pnucene.2016.03.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
5
|
Domènech C, García D, Pękala M. Decreasing Kd uncertainties through the application of thermodynamic sorption models. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 527-528:297-305. [PMID: 25965043 DOI: 10.1016/j.scitotenv.2015.04.107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 04/21/2015] [Accepted: 04/25/2015] [Indexed: 06/04/2023]
Abstract
Radionuclide retardation processes during transport are expected to play an important role in the safety assessment of subsurface disposal facilities for radioactive waste. The linear distribution coefficient (Kd) is often used to represent radionuclide retention, because analytical solutions to the classic advection-diffusion-retardation equation under simple boundary conditions are readily obtainable, and because numerical implementation of this approach is relatively straightforward. For these reasons, the Kd approach lends itself to probabilistic calculations required by Performance Assessment (PA) calculations. However, it is widely recognised that Kd values derived from laboratory experiments generally have a narrow field of validity, and that the uncertainty of the Kd outside this field increases significantly. Mechanistic multicomponent geochemical simulators can be used to calculate Kd values under a wide range of conditions. This approach is powerful and flexible, but requires expert knowledge on the part of the user. The work presented in this paper aims to develop a simplified approach of estimating Kd values whose level of accuracy would be comparable with those obtained by fully-fledged geochemical simulators. The proposed approach consists of deriving simplified algebraic expressions by combining relevant mass action equations. This approach was applied to three distinct geochemical systems involving surface complexation and ion-exchange processes. Within bounds imposed by model simplifications, the presented approach allows radionuclide Kd values to be estimated as a function of key system-controlling parameters, such as the pH and mineralogy. This approach could be used by PA professionals to assess the impact of key geochemical parameters on the variability of radionuclide Kd values. Moreover, the presented approach could be relatively easily implemented in existing codes to represent the influence of temporal and spatial changes in geochemistry on Kd values.
Collapse
Affiliation(s)
| | - David García
- Amphos 21, Passeig de Garcia i Fària 49-51, 08019, Barcelona, Spain.
| | - Marek Pękala
- Amphos 21, Passeig de Garcia i Fària 49-51, 08019, Barcelona, Spain
| |
Collapse
|
6
|
Tachi Y, Ebina T, Takeda C, Saito T, Takahashi H, Ohuchi Y, Martin AJ. Matrix diffusion and sorption of Cs+, Na+, I- and HTO in granodiorite: Laboratory-scale results and their extrapolation to the in situ condition. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 179:10-24. [PMID: 26024950 DOI: 10.1016/j.jconhyd.2015.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 04/17/2015] [Accepted: 05/07/2015] [Indexed: 06/04/2023]
Abstract
Matrix diffusion and sorption are important processes controlling radionuclide transport in crystalline rocks. Such processes are typically studied in the laboratory using borehole core samples however there is still much uncertainty on the changes to rock transport properties during coring and decompression. It is therefore important to show how such laboratory-based results compare with in situ conditions. This paper focuses on laboratory-scale mechanistic understanding and how this can be extrapolated to in situ conditions as part of the Long Term Diffusion (LTD) project at the Grimsel Test Site, Switzerland. Diffusion and sorption of (137)Cs(+), (22)Na(+), (125)I(-) and tritiated water (HTO) in Grimsel granodiorite were studied using through-diffusion and batch sorption experiments. Effective diffusivities (De) of these tracers showed typical cation excess and anion exclusion effects and their salinity dependence, although the extent of these effects varied due to the heterogeneous pore networks in the crystalline rock samples. Rock capacity factors (α) and distribution coefficients (Kd) for Cs(+) and Na(+) were found to be sensitive to porewater salinity. Through-diffusion experiments indicated dual depth profiles for Cs(+) and Na(+) which could be explained by a near-surface Kd increment. A microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the surface of the samples. The Kd values derived from the dual profiles are likely to correspond to Kd dependence on the grain sizes of crushed samples in the batch sorption experiments. The results of the in situ LTD experiments were interpreted reasonably well by using transport parameters derived from laboratory data and extrapolating them to in situ conditions. These comparative experimental and modelling studies provided a way to extrapolate from laboratory scale to in situ condition. It is well known that the difference in porosity between laboratory and in situ conditions is a key factor to scale laboratory-derived De to in situ conditions. We also show that cation excess diffusion is likely to be a key mechanism in crystalline rocks and that high Kd in the disturbed surfaces is critically important to evaluate transport in both laboratory and in situ tests.
Collapse
Affiliation(s)
- Yukio Tachi
- Japan Atomic Energy Agency, Muramatsu 4-33, Tokai, Ibaraki, 319-1194, Japan.
| | - Takanori Ebina
- NESI Inc., Muramatsu 4-33, Tokai, Ibaraki, 319-1112, Japan
| | - Chizuko Takeda
- Tokyo Nuclear Service Inc., Midorigahara 4-19-2, Tsukuba, Ibaraki, 300-2646, Japan
| | - Toshihiko Saito
- Tokyo Nuclear Service Inc., Midorigahara 4-19-2, Tsukuba, Ibaraki, 300-2646, Japan
| | - Hiroaki Takahashi
- Japan Atomic Energy Agency, Muramatsu 4-33, Tokai, Ibaraki, 319-1194, Japan
| | - Yuji Ohuchi
- Inspction Development Co. Ltd., Muramatsu 4-33, Tokai, Ibaraki, 319-1112, Japan
| | | |
Collapse
|
7
|
|
8
|
Tachi Y, Ochs M, Suyama T. Integrated sorption and diffusion model for bentonite. Part 1: clay–water interaction and sorption modeling in dispersed systems. J NUCL SCI TECHNOL 2014. [DOI: 10.1080/00223131.2014.914452] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
9
|
Tachi Y, Yotsuji K, Suyama T, Ochs M. Integrated sorption and diffusion model for bentonite. Part 2: porewater chemistry, sorption and diffusion modeling in compacted systems. J NUCL SCI TECHNOL 2014. [DOI: 10.1080/00223131.2014.914453] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
10
|
Gückel K, Rossberg A, Müller K, Brendler V, Bernhard G, Foerstendorf H. Spectroscopic identification of binary and ternary surface complexes of Np(V) on gibbsite. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:14418-14425. [PMID: 24219402 DOI: 10.1021/es4034183] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
For the first time, detailed molecular information on the Np(V) sorption species on amorphous Al(OH)3 and crystalline gibbsite was obtained by in situ time-resolved Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results consistently demonstrate the formation of mononuclear inner sphere complexes of the NpO2(+) ion irrespective of the prevailing atmospheric condition. The impact of the presence of atmospheric equivalent added carbonate on the speciation in solution and on the surfaces becomes evident from vibrational data. While the 1:1 aqueous carbonato species (NpO2CO3(-)) was found to become predominant in the circumneutral pH range, it is most likely that this species is sorbed onto the gibbsite surface as a ternary inner sphere surface complex where the NpO2(+) moiety is directly coordinated to the functional groups of the gibbsite's surface. These findings are corroborated by results obtained from EXAFS spectroscopy providing further evidence for a bidentate coordination of the Np(V) ion on amorphous Al(OH)3. The identification of the Np(V) surface species on gibbsite constitutes a basic finding for a comprehensive description of the dissemination of neptunium in groundwater systems.
Collapse
Affiliation(s)
- Katharina Gückel
- Institute of Resource Ecology , Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | | | | | | | | | | |
Collapse
|
11
|
Fröhlich DR, Amayri S, Drebert J, Reich T. Influence of humic acid on neptunium(V) sorption and diffusion in Opalinus Clay. RADIOCHIM ACTA 2013. [DOI: 10.1524/ract.2013.2059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
SummaryThe influence of14C-labeled M42 humic acid (HA) on the interaction between neptunium(V) and natural clay rock (Opalinus Clay (OPA), Switzerland) has been investigated in batch sorption and diffusion experiments under ambient air conditions. The effect of 10 mg/L HA on the diffusion of 8 μM Np(V) in OPA has been investigated in synthetic OPA pore water (pH 7.6, I = 0.4M) for the first time. Batch sorption experiments as a function of solid-to-liquid ratio (4-20 g/L) were performed under same experimental conditions to compare distribution coefficients obtained from both diffusion and sorption experiments. These experiments showed only a slight influence of HA on Np(V) uptake by OPA in both cases and provided comparable distribution coefficients (presence of HA: Kd= 22-32 L/kg, absence of HA: Kd= 30-46 L/kg). As it is known that the interactions of humic substances with actinides depend on various experimental parameters, the effect of HA on Np(V) sorption on 15 g/L OPA was also investigated as a function of pH (6-10) and initial Np concentration (8 μM and 7 pM). A saturated calcite solution was used as a background electrolyte in this case to prevent any dissolution of calcite contained in OPA at low pH. The results showed that the presence of M42 HA increases Np(V) sorption at pH < 7 while lower sorption was obtained above pH 8. Higher sorption at acidic pH can be attributed to strong sorption of HA which increases the number of sorption sites, while sorption decreases at higher pH probably due to formation of soluble ternary neptunium humate carbonate species.
Collapse
Affiliation(s)
- D. R. Fröhlich
- Institue of Nuclear Chemistry, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - S. Amayri
- Institue of Nuclear Chemistry, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - J. Drebert
- Institue of Nuclear Chemistry, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - T. Reich
- Institue of Nuclear Chemistry, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| |
Collapse
|
12
|
Speciation of Np(V) uptake by Opalinus Clay using synchrotron microbeam techniques. Anal Bioanal Chem 2012; 404:2151-62. [DOI: 10.1007/s00216-012-6290-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 07/19/2012] [Accepted: 07/20/2012] [Indexed: 11/27/2022]
|