Bedrock Geosciences

Auenstein, Switzerland

Bedrock Geosciences

Auenstein, Switzerland
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Alexander W.R.,Bedrock Geosciences | Reijonen H.M.,Geological Survey of Finland | Mackinnon G.,Scottish Universities Environmental Research Center | Milodowski A.E.,British Geological Survey | And 2 more authors.
Geosciences (Switzerland) | Year: 2017

Bentonite makes an important contribution to the performance of the engineered barriers in most radioactive waste repository designs. The choice of bentonite results from its favourable properties for waste isolation and its stability in relevant geological environments. However, the longevity of bentonite (especially the resistance to waste container sinking) has been little studied. Modelling results suggest significant bentonite deformation and associated canister sinking is unlikely and, here, long-term natural system data are used as a reality check on model predictions. Results indicate that bentonite from the investigated site shows no significant deviation in bulk physical parameters from repository bentonite. However, micro-scale shear planes can be seen throughout the sampled cores. The presence of multi-directional Sand C-type shears suggests they originate from loading from the overlying limestone, not gravitational tectonics. The plastic limits and angles of shearing resistance for natural and repository bentonites suggest both are susceptible to shearing. The impact of bentonite shear under load could be minimised by appropriate design, but existing lower activity waste container designs do not consider the potentially high external stresses from the bentonite backfill and this should be addressed in future. © 2017 by the authors; licensee MDPI, Basel, Switzerland.


Alexander W.R.,Bedrock Geosciences | Milodowski A.E.,British Geological Survey | Pitty A.F.,Pitty EIA Consulting | Hardie S.M.L.,Scottish Enterprise | And 5 more authors.
Mineralogical Magazine | Year: 2012

The Cyprus Natural Analogue Project was carried out due to the requirement to support ongoing laboratory and modelling efforts on the potential reaction of the bentonite buffer with cementitious leachates in the repository engineered barrier system. Although it is known that the higher pH (12.5 - 13) leachates from ordinary Portland cement will degrade bentonite, it is unclear if this will also be the case for the lower pH (10-11) leachates typical of low alkali cements. Ongoing laboratory and underground rock laboratory programmes, which are currently investigating this, face the obstacle of slow kinetics and the production of short-lived metastable phases, meaning obtaining unambiguous results may take decades. It was therefore decided to implement a focussed natural analogue study on bentonite/low alkali cement leachate reactions to provide indications of the probable long-term reaction products and reaction pathways to provide feedback on the existing short-term investigations noted above and to ascertain if any critical path research and development needs to be instigated now. The results of the analyses presented here, in this short overview of the project, suggest that there has been very limited alkaline groundwater reaction with the bentonite. This is generally supported by both the geomorphological evidence and the natural decay series data which imply groundwater/rock interaction in the last 105 a. © 2012 The Mineralogical Society.


Alexander W.R.,Bedrock Geosciences | Milodowski A.E.,British Geological Survey | Pitty A.F.,Pitty EIA Consulting | Hardie S.M.L.,Scottish Universities Environmental Research Center | And 5 more authors.
Clay Minerals | Year: 2013

Bentonite is one of the more safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. It is used due to its favourable properties (including plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides) and its stability in relevant geological environments. However, bentonite is unstable under alkaline conditions and this has driven interest in low-alkali cements (leachate pH of 10 À 11). To build a robust safety case, it is important to have supporting natural analogue data to confirm understanding of the likely long-term performance of bentonite. In Cyprus, the presence of natural bentonite in close proximity to natural alkaline groundwaters permits the zones of potential bentonite/alkaline water reaction to be studied as an analogy of the potential reaction zones in the repository. Here, the results indicate minimal volumetric reaction of bentonite, with production of a palygorskite secondary phase. © 2013 Mineralogical Society.


Alexander W.R.,Bedrock Geosciences | Reijonen H.M.,Saanio & Riekkola Oy | McKinley I.G.,MCM Consulting
Swiss Journal of Geosciences | Year: 2015

The geological disposal of radioactive wastes is generally accepted to be the most practicable approach to handling the waste inventory built up from over 70 years accumulation of power production, research–medical–industrial and military wastes. Here, a brief overview of the approach to geological disposal is presented along with some information on repository design and the assessment of repository post-closure safety. One of the significant challenges for repository safety assessment is how to extrapolate the likely long-term (i.e. ten thousand to a million years) behaviour of the repository from the necessarily short term data from analytical laboratories and underground rock laboratories currently available. One approach, common to all fields of the geosciences, but also in such diverse fields as philosophy, biology, linguistics, law etc., is to utilise the analogue argumentation methodology. For the specific case of radioactive waste management, the term ‘natural analogue’ has taken on a particular meaning associated with providing supporting arguments for a repository safety assessment. This approach is discussed here with a brief overview of how the study of natural (and, in particular, geological) systems can provide supporting information on the likely long-term evolution of a deep geological waste repository. The overall approach is discussed and some relevant examples are presented, including the use of uranium ore bodies to assess waste form stability, the investigation of native metals to define the longevity of waste containers and how natural clays can provide information on the stability of waste tunnel backfill material. © 2015, Swiss Geological Society.


Reijonen H.M.,Saanio & Riekkola Oy | Alexander W.R.,Bedrock Geosciences
Swiss Journal of Geosciences | Year: 2015

The practice of utilising natural analogues in assessing the long-term behaviour of various components of geological repositories for radioactive waste is already well established in most disposal programmes. Numerous studies on bentonites, focussing on bentonite interaction with other components of the engineered barrier system and a range of host rock environments, are present in the literature. In this article, recent bentonite natural analogue studies are briefly reviewed, and gaps in the current literature identified, with the aim of (1) suggesting where relevant new information could be obtained by data mining published bentonite natural analogue studies with a new focus on current safety case requirements, (2) collecting relevant information by revisiting known bentonite analogue sites and conducting investigations with more appropriate analytical techniques, and (3) identifying novel study sites where, for example, bentonite longevity in very dilute to highly saline groundwater conditions can be studied. It must be noted that the use of natural analogues in safety case development is likely to be site and repository design-specific in nature and thus emphasis is placed on the appropriate use of relevant natural analogue data on bentonite longevity. © 2015, Swiss Geological Society.


Reijonen H.M.,Saanio & Riekkola Oy | Russell Alexander W.,Bedrock Geosciences | Marcos N.,Saanio & Riekkola Oy | Lehtinen A.,Posiva Oy
Swiss Journal of Geosciences | Year: 2015

A report entitled “complementary considerations” has recently been published by Posiva, the organization implementing the spent fuel disposal programme in Finland. It is part of the documentation (called TURVA-2012 safety case) submitted in 2012 for the construction license for a deep geological repository at the Olkiluoto site in Finland. The complementary considerations report addresses diverse and less quantifiable types of evidence and arguments for long-term safety which enhance confidence in the outcome of the safety assessment, especially for times greater than a few thousand years. Natural analogues form the core of the “complementary considerations” with the focus very much on geological occurrences of materials and/or processes which mirror those in the repository. For example, native copper is found in fractures in the Fennoscandian Shield and an understanding of its persistence would be of use when assessing the likely lifetime of the copper canister which surrounds the spent fuel. Based on the outcome of this Olkiluoto site specific report, research topics have been identified in relation to processes affecting the performance and future behaviour of the engineered barrier system materials, especially in relation to corrosion of copper and iron (used in waste container outer shell and insert, respectively), alteration and deformation of the bentonite buffer (clay used in the voids between the waste container and bedrock) and interaction with cementitious materials (tunnel supports etc.) “complementary considerations” is not the sole user of natural analogue information within the safety case, but its main aim is to allow thorough discussion and provide background that can be referred to in other safety case documentation, such as process descriptions, assessment of repository performance etc. © 2015, Swiss Geological Society.


Kunimaru T.,Japan Atomic Energy Agency | Ota K.,Japan Atomic Energy Agency | Amano K.,Japan Atomic Energy Agency | Alexander W.R.,Bedrock Geosciences
Proceedings of the International Conference on Radioactive Waste Management and Environmental Remediation, ICEM | Year: 2010

An appropriate QMS, which is among the first tools required for repository site characterisation, will save on effort by reducing errors and the requirement to resample and reanalyse - but this can only be guaranteed by continuously assessing if the system is truly fit-for-purpose and amending it as necessary based on the practical experience of the end-users on-site. A QA audit of hydrochemical datasets for boreholes HDB-1 - 11 from Horonobe URL project by JAEA has been carried out by the application of a formal QA analysis which is based on the methodology previously employed for groundwaters during the recent site characterisation programme in Sweden. This methodology has been successfully applied to the groundwaters of the fractured crystalline rocks of the Fennoscandian Shield and has now been adapted and applied to some of the ground- and porewaters of the Horonobe URL area. This paper will present this system in the context of the Japanese national programme and elucidate improvements made during hands-on application of the borehole investigation QMS. Further improvements foreseen for the future will also be discussed with a view of removing inter-operator variability as much as is possible. Only then can confidence be placed in URL project or repository site hydrochemical datasets. © 2010 by ASME.


Milodowski A.E.,British Geological Survey | Norris S.,Radioactive Waste Management Ltd RWM | Russell Alexander W.,Bedrock Geosciences
Applied Geochemistry | Year: 2016

Bentonite is one of the more safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. Bentonite is utilised because of its favourable properties which include plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides and stability in geological environments of relevance to waste disposal. However, bentonite is unstable under the highly alkaline conditions induced by Ordinary Portland Cement (OPC: initial porewater pH > 13) and this has driven interest in using low alkali cements (initial porewater pH9-11) as an alternative to OPC. To build a robust safety case for a repository for radioactive wastes, it is important to have supporting natural analogue data to confirm understanding of the likely long-term performance of bentonite in these lower alkali conditions. In Cyprus, the presence of natural bentonite in association with natural alkaline groundwater permits the zones of potential bentonite/alkaline water reaction to be studied as an analogy of the potential reaction between low alkali cement leachates and the bentonite buffer in the repository. Here, the results indicate that a cation diffusion front has moved some metres into the bentonite whereas the bentonite reaction front is restricted to a few millimetres into the clay. This reaction front shows minimal reaction of the bentonite (volumetrically, less than 1% of the bentonite), with production of a palygorskite secondary phase following reaction of the primary smectites over time periods of 105-106 years. © 2015 Elsevier Ltd.


McKinley I.G.,McKinley Consulting | Alexander W.R.,Bedrock Geosciences | Kawamura H.,Obayashi Corporation
Nuclear Engineering International | Year: 2011

Tsunami has the ability to impact a variety of nuclear facilities in different geographical settings and the risk is wider in the nuclear reactors in coastal areas. The impact of a tsunami of particular size is influenced by the source of the water displacement, particularly if it is a major earthquake and/or volcanic eruption relatively nearby. Major nuclear facilities may generally be sufficiently strong to withstand the initial impact of even large waves, but it has to be ensured that they are strong enough to resist also the high drag forces, which are rarely considered during design, but can greatly exceed the surge force for larger waves. It is also important that access hatches, ventilation intakes and so on are protected from flooding. It is essential to ensure that all critical infrastructure providing control, communication, monitoring, power, cooling, ventilation, drainage, transportation, etc. is protected from both mechanical damage and inundation. For protection of an entire site, tsunami walls are a common approach.


Arcilla C.A.,University of the Philippines at Diliman | Pascua C.S.,University of the Philippines at Diliman | Alexander W.R.,Bedrock Geosciences
Energy Procedia | Year: 2011

The potential of using ophiolites for CCS has been pointed out before, but no case study has been conducted for the Philippines. Here, the potential for CCS in both ophiolites in general and ophiolites in the Philippines in particular is examined and discussed. Specific drawbacks of using ophiolites as a CO 2 sink are presented for the first time, using information from natural analogue studies in the Philippines and Jordan. © 2010 Elsevier Ltd. © 2011 Published by Elsevier Ltd.

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