Properties of Bentonite Clay as Buffer Material in High-Level Waste Geological Disposal. Part I: Chemical Species Contained in Bentonite

1987 ◽  
Vol 76 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Masanori Takahashi ◽  
Masayuki Muroi ◽  
Atsuyuki Inoue ◽  
Masahiro Aoki ◽  
Makoto Takizawa ◽  
...  
Keyword(s):  
Chemical Species ◽  
Bentonite Clay ◽  
High Level Waste ◽  
Geological Disposal ◽  
Buffer Material ◽  
High Level

Laboratory and Modelling Studies of Sodium Benionite Grounmater Interaction

1986 ◽  
Vol 84 ◽  
Author(s):  
M. Sneujman ◽  
H. Uotiia ◽  
J. Rantanen
Keyword(s):  
Near Field ◽  
Chemical Species ◽  
Fluid Phase ◽  
High Level Waste ◽  
Sodium Bentonite ◽  
Model Calculations ◽  
Buffer Material ◽  
Modelling Studies ◽  
Calcite Saturation ◽  
High Level

AbstractAccording to the present Finnish concept sodium bentonite will be used as a buffer material in the repository for high-level waste. Experimental and theoretical studies treating the effect of bentonite upon the chemical conditions in a repository have been initiated with the object of specifying the chemistry of the near field.Sodium bentonite was let react with water under anaerobic conditions at 25°C for 540 days, during which time six fluid samples were extracted for the chemical analysis of 15 chemical species. The generated fluid phase was alkaline (PH = 9…10) and contained a high amount of bicarbonate. Also a low redox-potential was measured. The fluid phase chemistry was investigated using the geochemical code PHREEM. Calcite saturation was observed in all fluid samples.A modelling of sodium bentonite interaction with water based on the main mineral components of bentonite was also performed with PHREEQE. A fairly good agreement between experimental results and model calculations was observed.

Migration Behavior of Plutonium in Compacted Bentonite under Reducing Condition by Using Electromigration

2003 ◽  
Vol 807 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Xiaobin Xia ◽  
Yoshiro Kikuchi ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Initial Period ◽  
Chemical Species ◽  
High Level Waste ◽  
Migration Behavior ◽  
Buffer Material ◽  
Reducing Environment ◽  
High Level ◽  
Corrosion Of Iron ◽  
Reducing Condition

ABSTRACTCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. Carbon steel overpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The reducing condition will be expected to retard the migration of redox-sensitive radionuclides by lowering their solubilities. Therefore, the presence of corrosion products of iron in buffer material is important to discuss the migration behavior of redox-sensitive radionuclides. Plutonium electromigration experiments in bentonite have been carried out with source of iron ions supplied by anode corrosion of iron coupon. Plutonium migrated from the iron anode toward cathode as deep as 1 mm of the interior of bentonite within 24 h. Thus plutonium chemical species would have positive charge and were estimated as PuOH2+ or PuCl2+ by the thermodynamic calculation.

Performance Assessment of a High-Level-Waste Repository in Clay

1988 ◽  
Vol 127 ◽  
Author(s):  
Jan L. Marivoet ◽  
Geert Volckaert ◽  
Arnold A. Bonne
Keyword(s):  
Performance Assessment ◽  
Maximum Dose ◽  
High Level Waste ◽  
Clay Layer ◽  
Geological Disposal ◽  
Dose Rates ◽  
Consequence Analysis ◽  
Calculated Dose ◽  
Order Of Magnitude ◽  
High Level

ABSTRACTPerformance assessment studies have been undertaken on the geological disposal of high-level waste in a clay layer in the framework of the CEC project PAGIS. The methodology applied consists of two consecutive steps : a scenario and a consequence analysis. The scenario analysis has indicated that scenarios of normal evolution, of human intrusion, of climatic change, of secondary glaciation effects and of faulting should be evaluated. For the consequence analysis as well deterministic “best estimate” as stochastic calculations, including uncertainty, risk and sensitivity analyses, have been elaborated.The calculations performed show that most radionuclides decay to negligible levels within the first fewjneters of the clay barrier. Just a few radionuclides, 99Tc, 135Cs and 237Np with its daughter nuclides 233U and 229Th can eventually reach the biosphere. The maximum dose rates arising from the geological disposal of HLW, as evaluated by the “best-estimate” approach are about 10−11 Sv/y for river pathways. If the sinking of a water well into the 150 m deep aquifer layer in the vicinity of the repository is considered together with a climatic change, the maximum calculated dose rate rises to a value of 3×10−7 Sv/y. The maximum dose rates evaluated by stochastic calculations are about one order of magnitude higher due to the considerable uncertainties in the model parameters. In the case of the Boom clay the estimated consequences of a fault scenario are of the same order of magnitude as the results obtained for the normal evolution scenario. The maximum risk is estimated from the results obtained through stochastic calculations to be about 5×10−8 per year. The sensitivity analysis has shown that the effective thickness of the clay layer, the retention factors of Tc, Cs and Np, and the Darcy velocity in the aquifer are parameters which strongly influence the calculated dose rates.

Experimental Investigation on the Active Range of Sulfate-Reducing Bacteria for Geological Disposal

1994 ◽  
Vol 353 ◽  
Author(s):  
S. Fukunaga ◽  
H. Yoshikawa ◽  
K. Fujiki ◽  
H. Asano
Keyword(s):  
Experimental Investigation ◽  
Environmental Conditions ◽  
Desulfovibrio Desulfuricans ◽  
Sulfate Reducing Bacteria ◽  
Geological Disposal ◽  
Sulfate Reducing ◽  
Buffer Material ◽  
Ph Range ◽  
High Level ◽  
Reducing Bacteria

AbstractThe active range ofDesulfovibrio desulfuricans. a species of sulfate-reducing bacteria, was examined in terms of pH and Eh using a fermenter at controlled pH and Eh. Such research is important because sulfate-reducing bacteria (SRB) are thought to exist underground at depths equal to those of supposed repositories for high-level radioactive wastes and to be capable of inducing corrosion of the metals used in containment vessels.SRB activity was estimated at 35°C, with lactate as an electron donor, at a pH range from 7 to 11 and Eh range from 0 to -380 mV. Activity increased as pH approached neutral and Eh declined. The upper pH limit for activity was between 9.9 and 10.3, at Eh of -360 to -384 mV. The upper Eh limit for activity was between -68 and -3 mV, at pH 7.1. These results show that SRB can be made active at higher pH by decreasing Eh, and that the higher pH levels of 8 to 10 produced by use of the buffer material bentonite does not suppress SRB completely.A chart was obtained showing the active range ofDesulfovibrio desulfuricansin terms of pH and Eh. Such charts can be used to estimate the viability of SRB and other microorganisms when the environmental conditions of a repository are specified.

A resistivity-based approach to determining the rates of groundwater seepage into buffer materials

2019 ◽  
Vol 482 (1) ◽  
pp. 205-212 ◽  
Author(s):  
T. Ishii ◽  
M. Kawakubo ◽  
H. Asano ◽  
I. Kobayashi ◽  
P. Sellin ◽  
...  
Keyword(s):  
Water Solution ◽  
High Level Waste ◽  
Dry Density ◽  
Chemical Alteration ◽  
Constant Rate ◽  
Buffer Material ◽  
The Status ◽  
Engineered Barriers ◽  
High Level ◽  
Saturation Front

AbstractBentonite-based buffer materials play an important safety role in engineered barriers planned for use in geological disposal repositories for radioactive high-level waste (HLW) in Japan. The effectiveness of buffer materials is dependent on the status of groundwater saturation during resaturation of the repository. Accordingly, it is important to determine the behaviour of buffer materials during saturation and predict post-saturation conditions such as the distribution of residual dry density and chemical alteration.In this study, the rate of groundwater uptake into a buffer material was determined to clarify the behaviour of the material during the saturation process. As mechanical changes and chemical alteration of buffer materials are generated by groundwater permeation, knowledge of the water uptake rate is necessary for the prediction of post-permeation conditions. In the experiment reported here, one-dimensional permeation by distilled water and a NaCl water solution at a constant rate was monitored over a period of more than seven years. The results indicated that the seepage and saturation front moved in proportion to the square root of the seepage time. The coefficient of the relationships between the seepage and the saturation fronts with time of the reference bentonite used in Japan was determined.

scholarly journals State-of-the-art and proof-of-concept installations for repository concepts based in crystalline rock

2015 ◽  
Vol 79 (6) ◽  
pp. 1665-1673 ◽  
Author(s):  
Magnus Kronberg ◽  
Jan Gugala ◽  
Keijo Haapala
Keyword(s):  
Laser Scanning ◽  
Crystalline Rock ◽  
High Level Waste ◽  
Geological Disposal ◽  
Geological Repository ◽  
Reference Design ◽  
Potential Alternative ◽  
Deep Underground ◽  
High Level

AbstractOver the last five decades private and national energy programmes worldwide have been producing a variety of radioactive wastes. One of the safest ways of disposing of this waste is to bury it deep underground in purpose-built geological disposal facilities. Currently, there is no operating geological repository in Europe for high-level waste but the goal of the IGD-TP is that the first repository shall be fully operational before the year 2025. Several studies and experiments are ongoing at various potential repository sites in Europe with the goal to establish general approaches that can be adapted for any country in need of a geological repository.The Swedish Nuclear Fuel and Waste Management Co (SKB) in Sweden and Posiva Oy in Finland are developing a method for geological disposal of high-level long-lived nuclear waste in crystalline rock, the KBS-3 method. KBS-3V (vertical) is both organizations reference design, but KBS-3H (horizontal) emplacement is also being researched as a potential alternative. Of high importance in the development is demonstrating the technical feasibilityin situof safe and reliable construction, manufacturing, disposal and sealing of such geological disposal facilities. Parts of these demonstrations are carried out under the framework of EurAtom/FP7 and one of these projects is the LUCOEX project where SKB is demonstrating horizontal emplacement, the Multi Purpose Test (MPT), and Posiva is demonstrating vertical buffer installation processes.The MPT includes the key components of the horizontal design and comprises all essential steps; manufacturing of the full-scale components, their assembly, installation in the drift and monitoring of the early buffer evolution. The MPT installation was successfully performed in late 2013. By combining the components, an initial verification of the design implementation has been achieved. At the same time, integrating the components has meant the recognition of some design weaknesses and the design will be updated accordingly.Posiva's KBS-3V buffer installation equipment that places buffer blocks with high precision in vertical deposition holes is currently being developed and will be tested during 2014 and 2015 in real underground conditions. The machine uses vacuum lifting tools for moving the buffer blocks and laser scanning technology to position both the machine and blocks. Functionality of the concept and equipment selected will be confirmed by the tests and the installation tests will provide important information about the suitability of the selected buffer dimensions and tolerances.

Geological Disposal for High-Level Waste: Ethical Considerations

2001 ◽  
Author(s):  
Gustaaf C. Cornelis
Keyword(s):  
Time Scales ◽  
Waste Disposal ◽  
High Level Waste ◽  
Ethical Considerations ◽  
Technical Aspects ◽  
Geological Disposal ◽  
High Level

Abstract This paper describes the activities launched at SCK•CEN, intended to explore ethical and other non-technical aspects when dealing with the time scales considered in the high-level waste disposal program. (1) Especially the issues of retrievability and precaution will be focused on philosophically. Many questions will be raised in order to sensitize all stakeholders for the transdisciplinary character of the transgenerational problem at hand.

Manufacturing and Handling Techniques of the Monolithic Buffer Material for HLW Disposal

2001 ◽  
Author(s):  
Toshihiko Awano ◽  
Takeshi Kanno ◽  
Susumu Kawakami ◽  
Hiroyoshi Ueda ◽  
Takahiro Kimoto
Keyword(s):  
Radioactive Waste ◽  
Large Scale ◽  
Cold Isostatic Pressing ◽  
Large Block ◽  
Technical Feasibility ◽  
Geological Disposal ◽  
Buffer Material ◽  
Manufacturing Tests ◽  
High Level ◽  
Large Scale Tests

Abstract Small and large scale tests were performed to evaluate technical feasibility of the monolithic buffer material, defined as a large block of bentonite formed by the cold isostatic pressing, for geological disposal of high-level radioactive waste. Trial manufacturing tests up to approximately 70 [%]-scale of a Japanese disposal concept were carried out and emplacement tests were carried out by vacuum lifting and forklift-type methods for vertical and horizontal emplacement concepts, respectively. Based on the large engineering-scale tests, technical feasibility of the monolithic buffer was demonstrated.

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