Model for the Microbiological Corrosion of Copper Containers in a Deep Geologic Repository

2003 ◽  
Vol 807 ◽  
Author(s):  
Fraser King ◽  
Miroslav Kolar ◽  
Simcha Stroes-Gascoyne ◽  
Peter Maak
Keyword(s):  
Microbial Activity ◽  
Corrosion Behaviour ◽  
Geologic Repository ◽  
Microbiological Corrosion ◽  
Microbiological Processes ◽  
Bentonite Buffer ◽  
Buffer Material ◽  
The Impact ◽  
Aerobic And Anaerobic

ABSTRACTA model has been developed to predict the impact of microbiological processes on the long-term corrosion behaviour of copper containers in a deep geologic repository. The model accounts for a range of aerobic and anaerobic microbial processes. Various factors expected to limit the extent of microbial activity in the repository, such as the lack of water, evolving redox conditions, and the nutrient-poor environment, are taken into account in the model. Amongst other effects, the model predicts that microbial activity will not occur close to the container in the presence of highly compacted bentonite buffer material.

Methodology in Corrosion Testing of Container Materials for Radioactive Waste Disposal in a Geological Clay Repository

2001 ◽  
Author(s):  
Bruno Kursten ◽  
Frank Druyts ◽  
Pierre Van Iseghem
Keyword(s):  
Radioactive Waste ◽  
Corrosion Behaviour ◽  
Open Circuit ◽  
Geological Disposal ◽  
Boom Clay ◽  
Engineered Barriers ◽  
High Level ◽  
Aerobic And Anaerobic

Abstract The current worldwide trend for the final disposal of conditioned high-level, medium-level and long-lived alpha-bearing radioactive waste focuses on deep geological disposal. During the geological disposal, the isolation between the radioactive waste and the environment (biosphere) is realised by the multibarrier principle, which is based on the complementary nature of the various natural and engineered barriers. One of the main engineered barriers is the metallic container (overpack) that encloses the conditioned waste. In Belgium, the Boom Clay sediment is being studied as a potential host rock formation for the final disposal of conditioned high-level radioactive waste (HLW) and spent fuel. Since the mid 1980’s, SCK•CEN has developed an extensive research programme aimed at evaluating the suitability of a wide variety of metallic materials as candidate overpack material for the disposal of HLW. A multiple experimental approach is applied consisting of i) in situ corrosion experiments, ii) electrochemical experiments (cyclic potentiodynamic polarisation measurements and monitoring the evolution of ECORR as a function of time), and iii) immersion experiments. The in situ corrosion experiments were performed in the underground research facility, the High Activity Disposal Experimental Site, or HADES, located in the Boom clay layer at a depth of 225 metres below ground level. These experiments aimed at predicting the long-term corrosion behaviour of various candidate container materials. It was believed that this could be realised by investigating the medium-term interactions between the container materials and the host formation. These experiments resulted in a change of reasoning at the national authorities concerning the choice of over-pack material from the corrosion-allowance material carbon steel towards corrosion-resistant materials such as stainless steels. The main arguments being the severe pitting corrosion during the aerobic period and the large amount of hydrogen gas generated during the subsequent anaerobic period. The in situ corrosion experiments however, did not allow to unequivocally quantify the corrosion of the various investigated candidate overpack materials. The main shortcoming was that they did not allow to experimentally separate the aerobic and anaerobic phase. This resulted in the elaboration of a new laboratory programme. Electrochemical corrosion experiments were designed to investigate the effect of a wide variety of parameters on the localised corrosion behaviour of candidate overpack materials: temperature, SO42−, Cl−, S2O32−, oxygen content (aerobic - anaerobic),… Three characteristic potentials can be derived from the cyclic potentiodynamic polarisation (CPP) curves: i) the open circuit potential, OCP, ii) the critical potential for pit nucleation, ENP, and iii) the protection potential, EPP. Monitoring the open circuit potential as a function of time in clay slurries, representative for the underground environment, provides us with a more reliable value for the corrosion potential, ECORR, under disposal conditions. The long-term corrosion behaviour of the candidate overpack materials can be established by comparing the value of ECORR relative to ENP and EPP (determined from the CPP-curves). The immersion tests were developed to complement the in situ experiments. These experiments aimed at determining the corrosion rate and to identify the corrosion processes that can occur during the aerobic and anaerobic period of the geological disposal. Also, some experiments were elaborated to study the effect of graphite on the corrosion behaviour of the candidate overpack materials.

The Hydrogeologic Environment for a Proposed Deep Geologic Repository in Canada for Low and Intermediate Level Radioactive Waste

2011 ◽  
Author(s):  
Jonathan F. Sykes ◽  
Stefano D. Normani ◽  
Yong Yin ◽  
Mark R. Jensen
Keyword(s):  
Radioactive Waste ◽  
Solute Transport ◽  
Regional Scale ◽  
Intermediate Level ◽  
Geologic Repository ◽  
Site Specific ◽  
Ordovician Limestone ◽  
Intermediate Level Radioactive Waste ◽  
The Impact

A Deep Geologic Repository (DGR) for low and intermediate level radioactive waste has been proposed by Ontario Power Generation for the Bruce nuclear site in Ontario, Canada. As proposed the DGR would be constructed at a depth of about 680 m below ground surface within the argillaceous Ordovician limestone of the Cobourg Formation. This paper describes the hydrogeology of the DGR site developed through both site characterization studies and regional-scale numerical modelling analysis. The analysis provides a framework for the assembly and integration of the site-specific geoscientific data and examines the factors that influence the predicted long-term performance of the geosphere barrier. Flow system evolution was accomplished using both the density-dependent FRAC3DVS-OPG flow and transport model and the two-phase gas and water flow computational model TOUGH2-MP. In the geologic framework of the Province of Ontario, the DGR is located on the eastern flank of the Michigan Basin. Borehole logs covering Southern Ontario combined with site-specific data from 6 deep boreholes have been used to define the structural contours and hydrogeologic properties at the regional-scale of the modelled 31 sedimentary strata that may be partially present above the Precambrian crystalline basement rock. The regional-scale domain encompasses an approximately 18500km2 region extending from Lake Huron to Georgian Bay. The groundwater zone below the Devonian includes units containing stagnant water having high concentrations of total dissolved solids that can exceed 300g/L. The Ordovician sediments are significantly under-pressured. The horizontal hydraulic conductivity for the Cobourg limestone is estimated to be 2 × 10−14 m/s based on straddle-packer hydraulic tests. The low advective velocities in the Cobourg and other Ordovician units result in solute transport that is diffusion dominant with Peclet numbers less than 0.003 for a characteristic length of unity. Long-term simulations that consider future glaciation scenarios include the impact of ice thickness and permafrost. Solute transport in the Ordovician limestone and shale was diffusion dominant in all simulations. The Salina formations of the Upper Silurian prevented the deeper penetration of basal meltwater.

Ultrasonic Velocities Measurement in Compacted Bentonite-Sand Mixtures for Saturation Level Evaluation

2018 ◽  
Author(s):  
Shun Kimura ◽  
Hideharu Takahashi ◽  
Ari Hamdani ◽  
Masanori Aritomi ◽  
Susumu Ozaki ◽  
...  
Keyword(s):  
Water Content ◽  
Water Saturation ◽  
Radioactive Waste Disposal ◽  
Saturation Level ◽  
Degree Of Saturation ◽  
Ultrasonic Velocities ◽  
Compacted Bentonite ◽  
Bentonite Buffer ◽  
Buffer Material

Compacted bentonite materials are often considered as a buffer material in the geological radioactive waste disposal. This bentonite is expected to fill up the space between the waste and the surrounding ground by swelling. Therefore, understanding the surrounding ground, i.e., groundwater behavior in bentonite, as a buffer material, is essential in order to evaluate the bentonite buffer performance and guarantee long-term safety. The monitoring system of the water saturation level in compacted bentonite is required because water content in buffer material may influence its elastic properties. In this study, the correlation between water content and elasticity in unsaturated compressed bentonite was experimentally evaluated. The evaluation was done by measuring the sound velocity of both longitudinal wave and transverse wave. As a result, it can be confirmed that ultrasonic velocities could evaluate a degree of saturation and bulk modulus of compacted bentonite.

scholarly journals Experimental study on effect by cementation on self-sealing capability of bentonite buffer material

2020 ◽  
Vol 205 ◽  
pp. 10004
Author(s):  
Daichi Ito ◽  
Hideo Komine ◽  
Hailong Wang
Keyword(s):  
High Pressures ◽  
Swelling Pressure ◽  
Swelling Properties ◽  
Bentonite Buffer ◽  
Waste Container ◽  
Buffer Material ◽  
The Difference ◽  
Property Changes ◽  
High Level

In Japanese project for disposal of high-level radioactive waste, the self-sealing capability of bentonite buffer material, which results from the swelling deformation to fill the gaps between waste container and wall of disposal pit, must be retained thousands of years. However, because of the effect of high pressures, occurrence of cementation and property changes of the buffer material are a concern. Few studies had examined cementation effects because of the difficulties for simulating long-term alteration process experimentally. In this paper, swelling properties of consolidated buffer are regarded as similar as those of naturally consolidated bentonite ore. Therefore, three kinds of bentonite ores were used for experiments to elucidate influences of cementation on self-sealing capabilities. Undisturbed and reconstituted specimens were prepared to assess their swelling pressures after filling a preset gap in a swelling pressure apparatus. Results show that for Japanese ores, the swelling pressure of undisturbed specimens is about half that of reconstituted specimens. For American and Chinese ores, the difference of swelling pressure is greater when the preset gap is smaller. Results imply that effects of cementation on self-sealing capability are smaller when swelling deformation is allowed.

A Preliminary Postclosure Safety Assessment of OPG’s Proposed L&ILW Deep Geologic Repository, Canada

2009 ◽  
Author(s):  
Richard Little ◽  
John Avis ◽  
Nicola Calder ◽  
Nava Garisto ◽  
Paul Gierszewski ◽  
...  
Keyword(s):  
Waste Management ◽  
Safety Assessment ◽  
Generation Model ◽  
Geologic Repository ◽  
Gas Generation ◽  
Seal Failure ◽  
High Level ◽  
2D And 3D ◽  
The Impact

Ontario Power Generation (OPG) is proposing to build a Deep Geologic Respository (DGR) for Low and Intermediate Level Waste (L&ILW) near the existing Western Waste Management Facility at the Bruce site in the Municipality of Kincardine, Ontario. The Nuclear Waste Management Organization (NWMO), on behalf of OPG, is currently preparing an Environmental Impact Statement (EIS) and Preliminary Safety Report (PSR) for the proposed repository. This involves investigation of the site’s geological and surface environmental characteristics, conceptual design of the DGR, and technical studies to demonstrate the operational and long-term safety of the proposed facility. A preliminary postclosure safety assessment (SA) was undertaken in 2008 and 2009. Consistent with the guidelines for the preparation of the EIS for the DGR and the regulatory guide on assessing the long-term safety of radioactive waste management, the SA evaluated the DGR’s performance and its potential impact on human health and the environment through pathway analysis of contaminant releases, contaminant transport, receptor exposure and potential effects. Consideration was given to the expected long-term evolution of the repository and site following closure (the Normal Evolution Scenario) and four disruptive (“what if”) scenarios (Human Intrusion, Severe Shaft Seal Failure, Open Borehole, and Extreme Earthquake), which considered events with uncertain or low probability that could disrupt the repository system. Conceptual and mathematical models were developed and then implemented in a range of software tools including AMBER, to provide estimates of impacts such as dose, FRAC3DVS, for detailed 2D and 3D groundwater flow and transport calculations, and T2GGM, a code that couples the Gas Generation Model (GGM) and TOUGH2 and models the generation of gas in the repository and its subsequent 2D transport through the geosphere. Calculations have been undertaken to assess the impact of radionuclides on human and non-human biota and the impact of non-radioactive species on humans and the environment. The results indicate that the DGR system provides a high level of postclosure safety.

scholarly journals The hydration of bentonite buffer material revealed by modeling analysis of a long-term in situ test

2020 ◽  
Vol 185 ◽  
pp. 105360
Author(s):  
Liange Zheng ◽  
Hao Xu ◽  
Jonny Rutqvist ◽  
Matthew Reagan ◽  
Jens Birkholzer ◽  
...  
Keyword(s):  
In Situ Test ◽  
Modeling Analysis ◽  
Bentonite Buffer ◽  
Buffer Material

scholarly journals Longitudinal and Shear Wave Velocities Measurement in Compacted Bentonite for Water Content

2018 ◽  
Vol 43 ◽  
pp. 01016
Author(s):  
Shun Kimura ◽  
Kazumi Kitayama ◽  
Hideharu Takahashi ◽  
Kazushi Kimoto ◽  
Katsuyuki Kawamura ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Water Content ◽  
Degree Of Saturation ◽  
Ultrasonic Velocities ◽  
Compacted Bentonite ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Bentonite Buffer ◽  
Buffer Material

Bentonite is a good candidate of buffer material for disposal repository of high-level radioactive waste. Understanding groundwater behavior in bentonite buffer material is important in order to evaluate the bentonite buffer performance and guarantee long-term safety. Elastic constants of the bentonite buffer material are important parameters for the long-term safety. Water content in buffer material may have an influence on its elastic properties. For this reason, the monitoring system of the water saturation level in compacted bentonite is required. In this study, the ultrasonic velocity measurement method for evaluation of water content in compacted bentonite was proposed. At first, the effect of a degree of saturation in compacted bentonite on the longitudinal and shear wave velocities was investigated experimentally. In addition, the elastic property, bulk modulus, in unsaturated compacted bentonite were evaluated by ultrasonic velocities. As a result, it can be confirmed that ultrasonic velocities can evaluate a degree of saturation and bulk modulus of compacted bentonite.

Suppressed, but Not Forgotten

2011 ◽  
Vol 70 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Beat Meier ◽  
Anja König ◽  
Samuel Parak ◽  
Katharina Henke
Keyword(s):  
Memory Trace ◽  
Thought Suppression ◽  
Test Phase ◽  
Indirect Test ◽  
Final Test ◽  
Test Experiment ◽  
And Control ◽  
Cue Words ◽  
The Impact

This study investigates the impact of thought suppression over a 1-week interval. In two experiments with 80 university students each, we used the think/no-think paradigm in which participants initially learn a list of word pairs (cue-target associations). Then they were presented with some of the cue words again and should either respond with the target word or avoid thinking about it. In the final test phase, their memory for the initially learned cue-target pairs was tested. In Experiment 1, type of memory test was manipulated (i.e., direct vs. indirect). In Experiment 2, type of no-think instructions was manipulated (i.e., suppress vs. substitute). Overall, our results showed poorer memory for no-think and control items compared to think items across all experiments and conditions. Critically, however, more no-think than control items were remembered after the 1-week interval in the direct, but not in the indirect test (Experiment 1) and with thought suppression, but not thought substitution instructions (Experiment 2). We suggest that during thought suppression a brief reactivation of the learned association may lead to reconsolidation of the memory trace and hence to better retrieval of suppressed than control items in the long term.

Examining the Impact of the Disabled Youth Peer Development Initiative: What are the Long-Term Outcomes?

2003 ◽  
Author(s):  
Teresa Garate-Serafini ◽  
Jose Mendez ◽  
Patty Arriaga ◽  
Larry Labiak ◽  
Carol Reynolds
Keyword(s):  
Long Term Outcomes ◽  
The Disabled ◽  
The Impact
Sign in / Sign up

Export Citation Format

Share Document