Sakaki, Toshihiro*; Komatsu, Mitsuru*; Takeuchi, Ryuji
Vadose Zone Journal (Internet), 15(8), 7 Pages, 2016/08
In the Groundwater Recovery Experiment in Tunnel which is underway at the MIU, water saturation is one of the key parameters to monitor in order to understand the recovery processes. In this study, the process of saturation increase in the quasi-saturated zone where trapped discrete air phase affects saturation due to further increase in water pressure was studied. The relationship between the positive water pressure and saturation was measured by laboratory test using sands with trapped air bubbles and the effect of compression of bubbles on the changes in saturation was analyzed. The experimental results showed that the water pressure-saturation curves closely followed the relationship estimated solely based on the air bubble compression using Boyle's law. Based on this observation, a mathematical model was established to define the water pressure - saturation curve for the region where the water pressure is positive.
Tachi, Yukio; Ebina, Takanori*; Takeda, Chizuko*; Saito, Toshihiko*; Takahashi, Hiroaki*; Ouchi, Yuji*; Martin, A. J.*
Journal of Contaminant Hydrology, 179, p.10 - 24, 2015/08
Matrix diffusion and sorption are important processes in the assessment of radionuclide transport in crystalline rocks. Diffusion and sorption parameters for Cs, Na, I and HTO were determined by through-diffusion and batch sorption experiments using granodiorite samples from the Grimsel Test Site, Switzerland. The De values were in the order Cs, Na, HTO, I. The capacity factor and Kd values show the same trends. The dual depth profiles for Cs and Na can be interpreted by a near-surface Kd increment. The microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the sample surface. 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 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.
Soler, J. M.*; Landa, J.*; Havlova, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Eikenberg, J.*; Martin, A. J.*
Journal of Contaminant Hydrology, 179, p.89 - 101, 2015/08
Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na, Cs) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na and 1 cm for Cs. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities (De) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that De and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results.
Soler, J. M.*; Landa, J.*; Havlova, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Martin, A. J.*
Materials Research Society Symposium Proceedings, Vol.1665, p.85 - 91, 2014/09
Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na, Cs) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na and 1 cm for Cs. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities (e) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that e and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results, which have to be investigated in more detail.
Curti, E.*; Aimoz, L.*; Kitamura, Akira
Journal of Radioanalytical and Nuclear Chemistry, 295(3), p.1655 - 1665, 2013/03
Se is a major dose-determining redox-sensitive nuclide in safety analysis of radioactive waste disposal sites. In aqueous solutions, selenium forms soluble anionic species (SeO and SeO) that hardly sorb on negatively charged surfaces of common host-rock minerals. However, Se is known to have a strong affinity with sulphides and interacts with pyrite, a common minor mineral of argillaceous rocks being considered as host rocks for radioactive waste repositories in Switzerland etc. In this study, we present micro- and bulk X-ray spectroscopy data (-XRF, -XANES, and EXAFS) showing that, under nearly anoxic conditions, dissolved SeO and SeO sorb directly onto the pyrite surface and are subsequently reduced to Se with increasing ageing time (up to 8 months). These results suggest that the mobility of Se released from radioactive waste could efficiently be reduced through uptake on the pyrite surface followed by transformation into a sparingly soluble reduced form.
Soler, J. M.*; Landa, J.*; Havlov, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Martin, A.*
Nagra NAB 12-53, 80 Pages, 2013/02
An in-situ long-term diffusion (LTD) experiment was performed at the Grimsel Test Site (Switzerland). Tracers, HTO, Na, Cs, were continuously circulated through a packed-off borehole and the tracer concentrations in the solution was monitored for 2.5 years. Subsequently, the borehole section was overcored and the tracer profiles in the rock analyzed. The drop in activity for Cs in the solution was much pronounced. Transport distances were about 20 cm for HTO, 10 cm for Na and 1 cm for Cs. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusion coefficients () and rock capacity () values. There was a rather good agreement between the values from different teams, implied that and values in the BDZ are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results, which have to be investigated in more detail.
Martin, A. J.*; Umeda, Koji; Ishimaru, Tsuneari
Updates in Volcanology; New Advances in Understanding Volcanic Systems (Internet), p.119 - 148, 2012/09
The probabilistic approach can be developed with quite high levels of confidence and take into account extreme volcanic events. However, for regions with few or no volcanoes, there is a need to include additional geological, geophysical and/or geochemical data sets that may indicate the likelihood of future volcanism. This has been achieved using Bayesian inference in order to combine one or more sets of chemical or geophysical information to a priori assumptions of volcano spatio-temporal distributions yielding modified a posteriori probabilities.
Savage, D.*; Soler, J. M.*; Yamaguchi, Kohei; Walker, C.; Honda, Akira; Inagaki, Manabu; Watson, C.*; Wilson, J.*; Benbow, S.*; Gaus, I.*; et al.
Applied Geochemistry, 26(7), p.1138 - 1152, 2011/07
The use of cement and concrete as fracture grouting or as tunnel seals in a geological disposal facility for rad wastes creates potential issues concerning chemical reactivity. From a long term safety perspective, it is desirable to be able model these interactions and changes quantitatively. As part of the LCS (Long-term Cement Studies) project programme, a modelling inter-comparison has been conducted, involving the modelling of two experiments describing cement hadration and cement-rock reaction, with teams representing the NDA (UK), Posiva (Finland), and JAEA. This modelling exercise showed that the dominant reaction pathways in the two experiments are fairly well understood and are consistent between the different modelling teams, although significant differences existed amongst the precise parameterisation. Future modelling exercises of this type should focus on a suitable natural or industrial analogue that might aid assessing mineral-fluid reactions at these longer timescales.
Kamei, Gento; Alexander, W. R.*; Clark, I. D.*; Degnan, P.*; Elie, M.*; Khoury, H.*; Milodowski, A. E.*; Pitty, A. F.*; Salameh, E.*; Smellie, J. A. T.*
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.141 - 147, 2010/10
Honda, Akira; Inagaki, Manabu; Yamaguchi, Kohei; Walker, C.
Nagra NAB 10-07, p.66 - 116, 2010/03
This report was made as part of LCS (Long-term Cement Studies) that was an international project involving NAGRA, NDA, POSIVA and JAEA. A part of the in-situ experiment at Grimsel test site and the bench mark analysis in phase 1 is published in this report. In the bench mark analysis of the cement hydration reaction, there is a reasonable agreement between the measured and the predicted species in solution in terms of general trends being reproduced by the models produced by the three modelling groups. In the bench mark analysis of the chemical reaction of the granite in the environment with transportation and the high pH solution, the major trends in measured species concentrations could be reproduced by all models. The observed permeability profile could not be matched.
Alexander, W. R.*; Frieg, B.*; Ota, Kunio
Nagra NTB 00-07, 105 Pages, 2009/11
Nagra and JAEA worked together for nearly a decade on a Radionuclide Retardation Project (RRP) at Nagra's Grimsel Test Site in Switzerland with the main aim of enhancing the understanding of radionuclide transport/retardation in fractured rock. This report summarises the results of the final phase (1996-1998) of excavation project that is an integral part of RRP. It focuses on in situ characterisation of the shear zone structure and the behaviour of radionuclides that are relevant to repository post-closure safety, but are so strongly retarded by interaction with the shear zone rock that they are not expected to migrate through the dipole flow-field in experimentally reasonable time scales. The subsequent excavation of the experimental shear zone is detailed and the results of the laboratory analysis of the three-dimensional geological structure and of the distribution of injected radionuclides within the flow-field are presented.
Mri, A.*; Soler, P.*; Ota, Kunio; Havlov, V.*
Nagra NAB 07-42, 31 Pages, 2007/12
The Long-Term Diffusion (LTD) project, an integral part of Phase IV at the Grimsel Test Site, Switzerland, is an international cooperative project (HYRL, Finland; JAEA and AIST, Japan; NRI/RAWRA, Czech Republic; Nagra, Switzerland) and consists of a series of experiments which aims to obtain quantitative information on matrix diffusion under in situ conditions. The LTD is divided into four work packages, WP1-4. The in situ monopole diffusion experiment (WP1) is preceded by predictive modelling exercise to support the design of the in situ experiment and to increase confidence in the modelling of long-term and large-scale diffusion process by comparing the predictions with the experimental results. This report presents a short overview of the conceptual models and codes applied and the predicted tracer profiles in the rock matrix as well as the expected tracer concentration in the injection solution.
Mathieson, J.*; Hooper, A. J.*; Alexander, W. R.*; Shiotsuki, Masao; Kamei, Gento
Proceedings of International Waste Management Symposium 2006 (WM '06) (CD-ROM), 9 Pages, 2006/02
In January, 2005 an international workshop was held in Oxford, UK to discuss research progress in the disposability of transuranic (TRU) waste (also known as long-lived intermediate level waste. This was the third such workshop, with two previous ones being held in Switzerland in 1996 and Japan in 1999. Whilst TRU/ILW represents more complex wasteforms than high-level waste (HLW) or spent fuel (SF), it is recognised that it has not received the same amount of attention. This paper summarises the themes discussed at the workshop and the conclusions derived. Moreover, it provides a status report and future direction of work in relation to TRU and ILW wastes. The overall conclusion of the workshop was a recognition of the uncertainties surrounding the subject and outstanding issues where further work was required. However, there were no insurmountable obstacles to making safety cases for the disposal of TRU/ILW waste - safety assessment strategies were at a mature stage.
Birkhaser, P.*; Lacave, C.*; Ohara, Hidefumi; Niizato, Tadafumi
JNC-TY5410 2005-001, 26 Pages, 2005/04
The goal of this study was to determine the frequency dependent amplification function by calculation of the ratio between the surface response spectrum and the response spectrum at depth. A 1D model (CyberQuake) was used for the computations, because it could be concluded from the local geology that there are no significant 2D effects to be expected. Acceleration time histories from a weak motion local earthquake at a depth of 13 and 16 km recorded on July 20th (M 0.7) and August 18th (M 0.8) 2003 and from the Tokachi off-shore earthquake to the south of Hokkaido located some 430 to 450 km away from the borehole, recorded on September 26th (M 8.0) plus an aftershock recorded on September 27th 2003 were available as input data. All events are characterised by rather small acceleration values. The amplifications seem to be magnitude dependent. With the data at hand, the observed amplification functions are however rather unstable, showing different shapes for the different earthquakes and for two components of a single event. The observed ground motion amplification was much higher than the one calculated. Possible explanations for the observed discrepancy are (1) an incorrectness in the derivation of the input S-wave velocity profile used for the calculations of this study, or (2) problems with the recording instruments It is therefore recommended to check the basis of the derivation of the S-wave velocity input data and, if possible, perform direct S-wave downhole logging or S-wave crosshole measurements. It is further recommended to plan for an installation of high quality accelerometers in the future JNC Horonobe URL shaft. Additional measurements of field data would allow to record a more reliable dataset for proving and characterising significant attenuation of earthquake accelerations with depth, which also will be an important argument for feasibility studies related to the site investigations for geological disposal elsewhere in Japan or worldwide.
Neall, F. B.*; Smith, P. A.*
JNC-TY1400 2004-001, 144 Pages, 2004/05
H12 report was examined from a wider perspective. It is concluded that H12 provides a clear and well-founded message that it is feasible to site and construct a safe repository from HLW in Japan.
Kamei, Gento; Alexander, W. R.*; Clark, I. D.*; Degnan, P.*; Elie, M.*; Khoury, H.*; Mader, U.*; Milodowski, A. E.*; Pitty, A. F.*; Salameh, E.*; et al.
no journal, ,
Marin, A.*; Siitari-Kauppi, M.*; Havlov, V.*; Tachi, Yukio; Miksova, J.*
no journal, ,
Matrix diffusion is very important in the context of the performance assessment of radioactive waste repository in the crystalline rocks. An in-situ long-term diffusion (LTD) project has been performed at the Grimsel Test Site, Switzerland, to realistically evaluate matrix diffusion of radionuclides in crystalline rock with minimal disturbance to in-situ conditions. As part of phase-I, tracers, HTO, Na-22, Cs-134, were continuously circulated through a packed-off borehole and the tracer concentrations in the solution was monitored for 2.5 years. Subsequently, the borehole section was overcored and the tracer profiles in the rock analyzed. These results were analyzed with diffusion-sorption models by different teams. The phase-II plans including experimental design and tracers selection will be discussed.
Tachi, Yukio; Ebina, Takanori*; Takahashi, Hiroaki; Nemoto, Kazuaki; Suyama, Tadahiro*; Martin, A.*
no journal, ,
Matrix diffusion and sorption of radionuclides in crystalline host rocks are key processes controlling safe geological disposal of radioactive waste. Diffusion and sorption parameters for Cs, Na, I and HTO were determined by laboratory experiments using granodiorite samples from the Grimsel Test Site, Switzerland. The De values derived were in the order Cs Na HTO I. The capacity factor and Kd values show the same trends. Depth profiles of Cs and Na obtained by abrasing samples after a diffusion period showed typical dual profiles. The results of in-situ long-term diffusion tests at GTS were interpreted by using GoldSim code and transport parameters based on laboratory results and their extrapolations to in-situ conditions. These model calculations could the in-situ LTD results of Cs and Na reasonably well, although it was difficult to interpret HTO results. Key findings from these comparative studies between laboratory experiments and in-situ LTD tests were discussed.
Martin, A.*; Ishimaru, Tsuneari; Umeda, Koji; Asamori, Koichi
no journal, ,
In Japan, numerous studies have been carried out to assess the stability of the geological environment including in particular, the spatio-temporal distribution of active faulting in the context of site selection of a radioactive waste repository and/or assessing the safety of current nuclear facilities etc. One key concern is the existance of active faults that do not show any surface rupture. High He-3/He-4 ratios which tend to be found in volcanic regions have also been measured in non-volcanic regions. This has been attributed to degassing from the mantle with faults potentially acting as conduits. Studies carried out in the western Tottori district have shown the potential of using He/He ratios as a means of providing indirect evidence of the existence of source fault(s) that caused the 6 Oct 2000 Tottori earthquake (Mw 6.8), but which had no apparent surface indication prior to the earthquake.
Havlova, V.*; Martin, A. J.*; Siitari-Kauppi, M.*; Tachi, Yukio
no journal, ,
The Long Term Diffusion Project (LTD) is an international project consisting of a series of experiments that aim was to obtain quantitative information on matrix diffusion under in situ conditions. In the 1st in-situ diffusion experiment, radionuclides (H, Na, Cs) were injected into the borehole in undisturbed rock matrix in Grimsel test site. The activity decrease was observed by regular sampling of the experimental solution in the system. After 800 days, the system was closed and the borehole was overcored. The active rock, surrounding the experimental interval, was then sawed and the tracer profiles were measured in the rock samples in order to determine the diffusion extent. Non sorbing H migrated up to 17 cm into the rock matrix. Na as slightly sorbing tracer migrated up to 7 cm. Finally, sorbing Cs migrated surprisingly up to 1.5 cm, instead expected several mms. The analyses results were afterwards used as a base for post mortem modelling.