Decrease of radionuclide sorption in hydrated cement systems by organic ligands; Comparative evaluation using experimental data and thermodynamic calculations for ISA/EDTA-actinide-cement systems

Ochs, M.*; Dolder, F.*; Tachi, Yukio

Applied Geochemistry, 136, p.105161_1 - 105161_11, 2022/01

https://doi.org/10.1016/j.apgeochem.2021.105161

Various types of radioactive wastes and environments contain organic substances that can stabilize the aqueous complexes with radionuclides and therefore lead to a decrease of sorption. The present study focuses on testing a methodology to quantify sorption reduction factors (SRFs) in the presence of organic ligands for cement systems. Three approaches for the estimation of SRFs; (1) analogy with solubility enhancement factors, (2) radionuclide speciation based on the thermodynamic calculations, and (3) experimental sorption data in ternary systems, were coupled and tested for the representative organic ligands (ISA and EDTA) and selected key radionuclides (actinides). Our approach allows to critically evaluate the dependence of SRFs for various systems on the chosen method of quantification, in accordance with the data availability for a given systems. The reliable SRFs can only be derived from the sorption measurements in ternary systems. SRF often need to be derived in the absence of such direct evidence, and estimations need to be made based on analogies and speciation information. However, such estimates may be subject to substantial uncertainties.

The Impact of cement on argillaceous rocks in radioactive waste disposal systems; A Review focusing on key processes and remaining issues

Wilson, J.*; Bateman, K.; Tachi, Yukio

Applied Geochemistry, 130, p.104979_1 - 104979_19, 2021/07

https://doi.org/10.1016/j.apgeochem.2021.104979

The concept of deep geological disposal will include the multiple use of cement-based materials. In the case of argillaceous host rocks, the presence of hyperalkaline cement porefluid results in the destabilization of primary minerals in the argillite, resulting in the development of a zone of alteration at cement-rock interfaces. The process understanding gained from experimental, analogue, and modelling studies has been reviewed, and remaining areas of uncertainty identified. Although there is a reasonably good understanding of the mineral assemblages that are likely to occur due to cement-rock interactions, there are still some areas where a degree of uncertainty remains, in particular: the evolution of cement-argillite interfaces at T 25C; the rates at which secondary minerals form; the extent of pore clogging due to secondary mineral precipitation; the implications of alteration for radionuclide transport.

Degassing behavior of noble gases from groundwater during groundwater sampling

Nakata, Kotaro*; Hasegawa, Takuma*; Solomon, D. K.*; Miyakawa, Kazuya; Tomioka, Yuichi*; Ota, Tomoko*; Matsumoto, Takuya*; Hama, Katsuhiro; Iwatsuki, Teruki; Ono, Masahiko*; et al.

Applied Geochemistry, 104, p.60 - 70, 2019/05

https://doi.org/10.1016/j.apgeochem.2019.03.007

no abstracts in English

Characterization of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and their post-closure behavior from a simulated underground facility

Iwatsuki, Teruki; Munemoto, Takashi*; Kubota, Mitsuru*; Hayashida, Kazuki; Kato, Toshihiro*

Applied Geochemistry, 82, p.134 - 145, 2017/05

AA2017-0090.pdf:2.35MB

https://doi.org/10.1016/j.apgeochem.2017.04.016

This study investigated the behavior of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and in a sealed drift at a depth of 500 m in the Mizunami Underground Research Laboratory (URL) in Japan. Approximately 10%60% of REEs in groundwater are associated with suspended particles. Carbonate particles in groundwater are most likely derived from in situ precipitation of supersaturated carbonate minerals such as calcite. Thermodynamic calculations show that the dissolved REE carbonate complexes in the closed drift decreased in the drift closure period. These complexes may have been absorbed or co-precipitated within the shotcrete on the drift wall. The usage of cement based materials would generate environmental conditions in which REEs are fundamentally immobile in and around the underground facilities.

The Role of low-temperature organic matter diagenesis in carbonate precipitation within a marine deposit

Miyakawa, Kazuya; Ishii, Eiichi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*

Applied Geochemistry, 76, p.218 - 231, 2017/01

https://doi.org/10.1016/j.apgeochem.2016.11.001

no abstracts in English

Interpretation of undisturbed hydrogeochemical conditions in Neogene sediments of the Horonobe area, Hokkaido, Japan

Sasamoto, Hiroshi; Arthur, R. C.*; Hama, Katsuhiro

Applied Geochemistry, 26(8), p.1464 - 1477, 2011/08

https://doi.org/10.1016/j.apgeochem.2011.05.020

It is important to evaluate the undisturbed hydrochemical conditions in deep underground for considering the initial geochemical setting of performance assessment of high level radioactive waste. In the present study, groundwater data obtained thorough the initial surface-based investigation at the Horonobe URL were used to check the correlation and reliability of data based on empirical, geostatistical and geochemical modeling techniques. Applicability of these techniques were discussed in the present study and the representative undisturbed hydrochemical conditions were estimated.

Redox front formation in an uplifting sedimentary rock sequence; An Analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste

Yoshida, Hidekazu; Metcalfe, R.*; Yamamoto, Koshi*; Amano, Yuki; Hoshii, Daisuke*; Kanekiyo, Akiko*; Naganuma, Takeshi*; Hayashi, Toru*

Applied Geochemistry, 23(8), p.2364 - 2381, 2008/08

https://doi.org/10.1016/j.apgeochem.2008.03.015

Subsurface redox fronts control the mobilization and fixation of many trace elements. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. The water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-ooxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure.

I/I ratios in Scottish coastal surface sea water; Geographical and temporal responses to changing emissions

Schnabel, C.*; Olive, V.*; Atarashi-Andoh, Mariko; Dougans, A.*; Ellam, R. M.*; Freeman, S.*; Maden, C.*; Stocker, M.*; Synal, H.-A.*; Wacker, L.*; et al.

Applied Geochemistry, 22(3), p.619 - 627, 2007/03

https://doi.org/10.1016/j.apgeochem.2006.12.007

The present work constitutes the first survey of iodine isotope ratios for Scottish seawater, including the first data for the west of Scotland. I/I ratios in the south-west Scotland reached 310 in 2004. Iodine isotope ratios increased by about a factor of 6 from 1992 to 2003 in the north-east of Scotland, in agreement with the increase of liquid I emissions from Sellafield over that time period.

Association of dissolved radionuclides released by the Chernobyl accident with colloidal materials in surface water

Matsunaga, Takeshi; Nagao, Seiya*; Ueno, Takashi; Takeda, Seiji; Amano, Hikaru; Tkachenko, Y.*

Applied Geochemistry, 19(10), p.1581 - 1599, 2004/10

https://doi.org/10.1016/j.apgeochem.2004.02.002

The association of dissolved Sr, Pu and Am with natural colloids was investigated in surface waters in the Chernobyl nuclear accident area by means of ultrafiltration. Results suggest that Pu and Am isotopes were preferentially associated with dissolved humic substances (HS) of high molecular size. A model calculation of the complexation of Pu and Am with HS also supported the above. This study has expanded our understanding of the general role of natural organic colloids in dictating the chemical form of actinides in the surface aquatic environment.

A Natural attenuation of arsenic in drainage from an abandoned arsenic mine dump

Fukushi, Keisuke*; Sasaki, Miwa*; Sato, Tsutomu*; Yanase, Nobuyuki; Amano, Hikaru; Ikeda, Hodaka*

Applied Geochemistry, 18(8), p.1267 - 1278, 2003/08

https://doi.org/10.1016/S0883-2927(03)00011-8

At Nishinomaki abandoned mine district, the water is acidic and contains much amounts of arsenic. However, arsenic concentration decreases downward without any artificial treatment. To understand the mechanism of the natural attenuation, the acid mine drainage and the ochreous precipitates were collected. The samples were analyzed by XRD, IR, ICP-MS and ion-chromatograph. The precipitates were investigated by selective extraction procedure. These results were interpreted with those calculated by the geochemical code. The contamination of water has been result from oxidation of pyrite and realgar and subsequent release of iron. The released ferrous iron transforms to ferric form by bacterial oxidation and then schwertmannite forms immediately. While the arsenic concentrations in the stream are lowered to background level at downstream, these in the ochreous precipitates are up to 60 mg/g. The iron hydroxide has been known to exhibit the high sorption affinity to arsenate. Hence, arsenic is effectively removed by the schwertmannite from the contaminated water and attenuated naturally.