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Journal Articles

A Scaling approach for retention properties of crystalline rock; Case study of the in-situ long-term sorption and diffusion experiment (LTDE-SD) at the $"A$sp$"o$ Hard Rock Laboratory in Sweden

Tachi, Yukio; Ito, Tsuyoshi*; Gylling, B.*

Water Resources Research, 57(11), p.e2020WR029335_1 - e2020WR029335_20, 2021/11

 Times Cited Count:2 Percentile:19.4(Environmental Sciences)

This paper focuses on the scaling approach for sorption and diffusion parameters from laboratory to in-situ conditions using the dataset of LTDE-SD experiment performed at the $"A$sp$"o$ HRL. The near-surface heterogeneities at both fracture surface and rock matrix could be evaluated by conceptual model with high porosity and diffusivity, and sorption capacity, and their gradual change at the near-surface zones. The modelling results for non-sorbing Cl-36 and weak-sorbing Na-22 could validate the model concept and the parameter estimation of porosity and diffusivity, by considering the disturbed zone of 5 mm thickness with gradual parameter changes. The De values of these cationic and anionic tracers showed typical cation excess and anion exclusion effects. The modelling results for high sorbing tracers (Cs-137, Ra-226, Ni-63 and Np-237) with different sorption mechanism could confirm the validity of the scaling approaches of Kd values as a function of particle size and their relation to the near-surface disturbances.

Journal Articles

Quantifying the porosity of crystalline rocks by in situ and laboratory injection methods

M$"o$ri, A.*; Mazurek, M.*; Ota, Kunio; Siitari-Kauppi, M.*; Eichinger, F.*; Leuenberger, M.*

Minerals (Internet), 11(10), p.1072_1 - 1072_17, 2021/10

 Times Cited Count:2 Percentile:24.14(Geochemistry & Geophysics)

Journal Articles

Behavior of YSZ based rock-like oxide fuels under simulated RIA conditions

Nakamura, Takehiko; Kusagaya, Kazuyuki*; Sasajima, Hideo; Yamashita, Toshiyuki; Uetsuka, Hiroshi

Journal of Nuclear Science and Technology, 40(1), p.30 - 38, 2003/01

 Times Cited Count:4 Percentile:31.71(Nuclear Science & Technology)

Pulse irradiation tests of three types of ROX fuel, i.e. YSZ single phase, finely mixed two phase composite of YSZ and spinel, and the other composite of larger YSZ particles dispersed in spinel matrix, were conducted in the NSRR to investigate their behavior under RIA conditions. Owing to their lower melting temperatures than that of UO$$_{2}$$ fuel, melting of ROX fuel occurred while the cladding was still solid and intact in the accident conditions. Therefore, consequence of the ROX fuel failure was quite different from that of UO$$_{2}$$ fuel. When the ROX fuels failed, a considerable amount of the molten fuel was released out to the surrounding coolant water. In spite of the release, no significant mechanical energy generation due to fuel/coolant thermal interaction was observed in the tested enthalpy range below 12 GJ/m$$^{3}$$. In terms of the failure threshold, on the other hand, the ROX fuels failed at fuel volumetric enthalpies above 10 GJ/m$$^{3}$$, which was comparable to that of UO$$_{2}$$ fuel. The results highlighted controlling parameters on the fuel behavior under the RIA conditions.

Journal Articles

Rock-like oxide fuels and their burning in LWRs

Yamashita, Toshiyuki; Kuramoto, Kenichi; Akie, Hiroshi; Nakano, Yoshihiro; Shirasu, Noriko; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Omichi, Toshihiko*

Journal of Nuclear Science and Technology, 39(8), p.865 - 871, 2002/08

 Times Cited Count:25 Percentile:81.57(Nuclear Science & Technology)

Research on the plutonium rock-like oxide (ROX) fuels and their once-through burning in light water reactors has been performed to establish an option for utilizing and disposing effectively the excess plutonium. The ROX fuel is a sort of the inert matrix fuels and consists of mineral-like compounds such as yttria stabilized zirconia, spinel and corundum. A particle-dispersed fuel was devised to reduce damage by heavy fission fragments. Some preliminary results on swelling, fractional gas release and microstructure change for five ROX fuels were obtained from the irradiation test and successive post-irradiation examinations. Inherent disadvantages of the Pu-ROX fuel cores could be improved by adding 238U or 232Th as resonant materials, and all improved cores showed a nearly the same characteristics as the conventional UO2 core during transient conditions. The threshold enthalpy of the ROX fuel rod failure was found to be comparable to the fresh UO2 rod by pulse-irradiation tests simulating reactivity initiated accident conditions.

Journal Articles

Diffusion of an ion in rock pore water and its relation to pore characteristics

*; ; *; *

Kozan Chishitsu, 40(5), p.323 - 336, 1990/00

no abstracts in English

Oral presentation

Modeling the in-situ long-term sorption and diffusion experiment (LTDE-SD) at the Aspo Hard Rock Laboratory in Sweden; Scaling approach from laboratory to in-situ condition

Tachi, Yukio; Ito, Tsuyoshi; Gylling, B.*

no journal, , 

The in-situ long-term sorption and diffusion experiment (LTDE-SD) at the Aspo Hard Rock Laboratory in Sweden provides valuable dataset to test the scaling approach from laboratory to in-situ condition. The scaling approach developed in the in-situ Long-Term Diffusion (LTD) project at Grimsel Test Site in Switzerland was tested for the LTDE-SD results as part of the SKB Task Force on modeling of groundwater flow and transport of solutes in fractured crystalline rocks. Our modelling approach could account reasonably overall trends for sorption and diffusion of 10 radionuclides, and was then evaluated as being applicable for a wider range of radionuclides and for more complex fracture systems.

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