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sp
HRLSawada, Atsushi; Sakamoto, Kazuhiko*; Watahiki, Takanori*; Imai, Hisashi*
SKB P-17-06, 154 Pages, 2023/08
Soler, J. M.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; Svensson, U.*; Iraola, A.*; Ebrahimi, K.*; Trinchero, P.*; Molinero, J.*; et al.
Nuclear Technology, 208(6), p.1059 - 1073, 2022/06
Times Cited Count：4 Percentile：45.99(Nuclear Science & Technology)The SKB Task Force is an international forum on modelling of groundwater flow and solute transport in fractured rock. The WPDE experiments are matrix diffusion experiments in gneiss performed at the ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing tracers was injected along a borehole interval. The objective of Task 9A was the predictive modelling of the tracer breakthrough curves from the WPDE experiments. Several teams, using different modelling approaches and codes, participated in this exercise. An important conclusion from this exercise is that the modelling results were very sensitive to the magnitude of dispersion in the borehole opening, which is related to the flow of water. Focusing on the tails of the breakthrough curves, which are more directly related to matrix diffusion and sorption, the results from the different teams were more comparable.
Finsterle, S.*; Lanyon, B.*; 
kesson, M.*; Baxter, S.*; Bergstr
m, M.*; Bockg
rd, N.*; Dershowitz, W.*; Dessirier, B.*; Frampton, A.*; Fransson, .*; et al.
Geological Society, London, Special Publications, No.482, p.261 - 283, 2019/00
Times Cited Count：9 Percentile：70.92(Geology)Nuclear waste disposal in geological formations relies on a multi-barrier concept that includes engineered components which in many cases includes a bentonite buffer surrounding waste packages and the host rock. An SKB's (Swedish Nuclear Fuel and Waste Management Co.) Modelling Task Force project facilitated to improve the overall understanding of rock - bentonite interactions, as 11 teams used different conceptualisations and modelling tools to analyse the in-situ experiment at the 
ps Hard Rock Laboratory. The exercise helped identify conceptual uncertainties that led to different assessments of the relative importance of the engineered and natural barrier subsystems and of aspects that need to be better understood to arrive at reliable predictions of bentonite wetting.
sp Laboratory, SwedenSasamoto, Hiroshi; Isogai, Takeshi*; Kikuchi, Hirohito*; Sato, Hisao*; Svensson, D.*
Clay Minerals, 52(1), p.127 - 141, 2017/03
Times Cited Count：3 Percentile：10.42(Chemistry, Physical)Compacted bentonite has been considered as a candidate of engineering barrier material in many countries for the safe disposal of high-level radioactive waste. SKB set up an in situ experiment (named ABM project) to compare the stability of different bentonites under the conditions exposed to an iron source and elevated temperature (up to 130
C as maximum) at the sp Hard Rock Laboratory, Sweden. Results for the Japanese bentonite (Kunigel V1) are summarized in the present paper. Mineralogical investigation using X-ray diffraction (XRD) and X-ray spectroscopy (SEM-EDX) suggested that no indication of smectite transformation or newly formed clay phases were observed. However, a distinct change of exchangeable cations of smectite was indicated (i.e., from Na type to Fe type) in the bentonite at the vicinity of the steel heater. Physical investigation by measurements of hydraulic conductivity and swelling property suggested that no significant change occur in the bentonite even at the vicinity of the steel heater. Such results might be considered due to the limited portion affected by the iron-bentonite interactions and partially occurred ion exchange reactions. Chemical investigation based on the measurements of methylane blue (MB), cation exchange capacity (CEC) and exchangeable cations showed that the lateral distribution for these parameters were basically constant without the significant gradient.
Sawada, Atsushi; Saegusa, Hiromitsu; Takeuchi, Shinji*; Sakamoto, Kazuhiko*; Dershowitz, W. S.*
SKB P-13-46, 82 Pages, 2015/12
Uchida, Masahiro; Dershowitz, W.*; Lee, G.*; Shuttle, D.*
Hydrogeology Journal, 17(5), p.1093 - 1110, 2009/07
Times Cited Count：9 Percentile：27.68(Geosciences, Multidisciplinary)This paper addresses a residual uncertainty after the in-situ tracer experiment and try to demonstrate the usefulness of tracer experiments for safety assessment. There have been long debate on the usefulness of in-situ tracer experiment, because the difference in temporal scale, where in-situ tracer experiments are generally conducted for the period of a few days to several months with high velocity to recover the tracers, whereas safety assessment requires more than ten thousand years with much slower velocity. This paper addresses the issue by comparing breakthrough curves for safety assessment conditions (long-term, slow velocity) with and without calibration to in-situ tracer experiment called STT-1b test at the Aspo Hard Rock Laboratory in Sweden. Authors newly developed a conceptual model of internal structure of fracture, which explicitly addresses fault gouge, coating minerals, altered zone and intact rock, since especially fault gouge has high porosity and likely to affect the tracer migration behavior. The result was that calibrated model showed much tighter distribution of breakthrough curve statistics indicating the constraining power of in-situ tracer experiment.
Soler, J. M.*; Lfgren, M.*; Nilsson, K.*; Lanyon, G. W.*; Gylling, B.*; Vidstrand, P.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; et al.
no journal, ,
The GWFTS Task Force is an international forum in the area of modeling of groundwater flow and solute transport in fractured rock. The WPDE experiments are matrix diffusion experiments in gneiss performed at the ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing radiotracers was injected along a borehole interval. The objective of Task 9A of Task Force was the predictive modeling of the tracer breakthrough curves from the WPDE experiments. Several teams, using different modeling approaches, participated in this exercise. An important conclusion from this exercise is that the modeling results were very sensitive to the magnitude of dispersion in the borehole opening, which is related to the flow of water. Focusing on the tails of the breakthrough curves, which are more directly related to matrix diffusion and sorption, the results from the different teams were more comparable.
