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Padovani C.,Radioactive Waste Management Ltd
Corrosion Engineering Science and Technology | Year: 2014

Radioactive Waste Management Limited (RWM), formerly the Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority (NDA RWMD), has a continuing programme of research and development to support the safe disposal of radioactive wastes in a geological disposal facility (GDF). This paper describes the part of RWM's research programme aimed at developing a robust understanding of the durability of container materials for a variety of potential wastes. It includes background information, a summary of relevant past and continuing R&D projects and, to a more limited extent, links to relevant scientific literature produced elsewhere. The paper considers separately the case of intermediate level waste (ILW), for which container materials are better defined, durability requirements are less stringent and the development of the disposal system in the UK is more mature, and that of high level waste (HLW) and spent fuel, for which a broader range of disposal options is being considered, durability requirements are more stringent and information available in the UK is currently largely based on international developments. © 2014 Institute of Materials, Minerals and Mining. Source

McEvoy F.M.,British Geological Survey | Schofield D.I.,British Geological Survey | Shaw R.P.,British Geological Survey | Norris S.,Radioactive Waste Management Ltd
Science of the Total Environment | Year: 2016

Identifying and evaluating the factors that might impact on the long-term integrity of a deep Geological Disposal Facility (GDF) and its surrounding geological and surface environment is central to developing a safety case for underground disposal of radioactive waste. The geological environment should be relatively stable and its behaviour adequately predictable so that scientifically sound evaluations of the long-term radiological safety of a GDF can be made. In considering this, it is necessary to take into account natural processes that could affect a GDF or modify its geological environment up to 1. million. years into the future. Key processes considered in this paper include those which result from plate tectonics, such as seismicity and volcanism, as well as climate-related processes, such as erosion, uplift and the effects of glaciation. Understanding the inherent variability of process rates, critical thresholds and likely potential influence of unpredictable perturbations represent significant challenges to predicting the natural environment. From a plate-tectonic perspective, a one million year time frame represents a very short segment of geological time and is largely below the current resolution of observation of past processes. Similarly, predicting climate system evolution on such time-scales, particularly beyond 200. ka AP is highly uncertain, relying on estimating the extremes within which climate and related processes may vary with reasonable confidence. The paper highlights some of the challenges facing a deep geological disposal program in the UK to review understanding of the natural changes that may affect siting and design of a GDF. © 2016. Source

Busby J.P.,British Geological Survey | Lee J.R.,British Geological Survey | Kender S.,British Geological Survey | Williamson P.,British Geological Survey | Norris S.,Radioactive Waste Management Ltd
Boreas | Year: 2016

The greatest thicknesses of permafrost in Great Britain most likely occurred during the last glacial-interglacial cycle, as this is when some of the coldest conditions occurred during the last 1 000 000 years. The regional development of permafrost across Great Britain during the last glacial-interglacial cycle was modelled from a ground surface temperature history based on mean annual temperatures and the presence of glacier ice. To quantify the growth and decay of permafrost, modelling was undertaken at six locations across Great Britain that represent upland glaciated, lowland glaciated, upland unglaciated and lowland unglaciated conditions. Maximum predicted permafrost depths derived in this academic study range between several tens of metres to over 100 m depending upon various factors including elevation, glacier ice cover, geothermal heat flux and air temperature. In general, the greatest maximum permafrost thicknesses occur at upland glaciated locations, with minimum thickness at lowland sites. Current direct geological evidence for permafrost is from surface or shallow processes, mainly associated with the active layer. Further research is recommended to identify the imprint of freeze/thaw conditions in permanently frozen porous rocks from beneath the active layer. © 2016 Collegium Boreas. Source

Purcell P.C.,International Nuclear Services | Carr N.,Radioactive Waste Management Ltd
Packaging, Transport, Storage and Security of Radioactive Material | Year: 2014

Radioactive Waste Management Limited (RWM) of the Nuclear Decommissioning Authority (NDA) is developing concepts to demonstrate the viability of using a standardised range of disposal canister (DC) designs for geological disposal of high level waste and spent fuel in the UK. The standardised DC are designed for disposal in a geological disposal facility with integrity requirements in the range 10 000 to 100 000 years. International Nuclear Services (INS) is also a subsidiary of the NDA and working with RWM to develop a design of packaging for transporting these DC, which is called the disposal canister transport container (DCTC). Initial studies undertaken by INS focused on optimising payload and geometry for the canister designs. Subsequent studies focused on achieving criticality safety requirements for transport, which established the use of multiple water barriers, were required for higher enriched spent fuels. The results of this initial work were presented at the International Nuclear Engineering society conference at London in 2012. Subsequently, RWM commissioned INS to develop the design of DCTC to a level where it would be viable for licensing as a transport package with appropriate level of technical understanding. A specific requirement of RWM was that the loaded DCTC should be capable of transportation on an existing design of four axle rail wagon, within a gross mass of 90 t, this giving considerable logistic and overall cost benefits. Recent development work has focused on detailed impact, thermal and shielding analysis and how these influence the DCTC transport mass and the position of that mass in relation to the four axle rail wagon, both of which influence its capability for the required transport. In terms of meeting mass limits, achieving the specified radiation shielding performance (neutron and gamma) for the spent fuel was found to be a major challenge. However, of equal challenge was to accommodate the high forces generated under impact accident conditions due to the high mass ratio of contents to container. In order to mitigate these forces, the shock absorber designs needed to be carefully judged because their dimensions were restricted by the rail wagon design. This paper describes the DCTC development work, how the design challenges were addressed and the conclusions reached. © W. S. Maney & Son Ltd 2014. Source

Lever D.,Amec Foster Wheeler | Vines S.,Radioactive Waste Management Ltd
Mineralogical Magazine | Year: 2015

Carbon-14 is a key radionuclide in the assessment of the safety of a geological disposal facility because of the calculated assessment of the radiological consequences of gaseous carbon-14-bearing species. Radioactive Waste Management Limited has established an Integrated Project Team (IPT) in which partners are working together to develop an holistic approach to carbon-14 management in the disposal system. We have used an 'AND' approach to structure and prioritize our technical work. For a waste stream to be of concern, there has to be a significant inventory, AND carbon-14-bearing gas has to be generated, AND this gas has to be entrained by bulk gas, AND it has to migrate through the engineered barriers, AND it has to migrate through the overlying geological environment (either as gas or in solution), AND there have to be consequences in the biosphere. We are also using this approach to consider alternative treatment, packaging and design options. © 2016 by Walter de Gruyter Berlin/Boston. Source

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