scholarly journals Understanding the likelihood and consequences of post-closure criticality in a geological disposal facility

2015 ◽  
Vol 79 (6) ◽  
pp. 1551-1561 ◽  
Author(s):  
R. J. Winsley ◽  
T. D. Baldwin ◽  
T. W. Hicks ◽  
R. M. Mason ◽  
P. N. Smith
Keyword(s):  
Spent Fuel ◽  
Geological Disposal ◽  
Safe Disposal ◽  
Waste Package ◽  
Disposal Facility ◽  
Safety Case ◽  
Operational Phase ◽  
Strength Rock ◽  
Criticality Safety

AbstractA geological disposal facility (GDF) will include fissile materials that could, under certain conditions, lead to criticality. Demonstration of criticality safety therefore forms an important part of a GDF's safety case.Containment provided by the waste package will contribute to criticality safety during package transport and the GDF operational phase. The GDF multiple-barrier system will ensure that criticality is prevented for some time after facility closure. However, on longer post-closure timescales, conditions in the GDF will evolve and it is necessary to demonstrate: an understanding of the conditions under which criticality could occur; the likelihood of such conditions occurring; and the consequences of criticality should it occur.Work has addressed disposal of all of the UK's higher-activity wastes in three illustrative geologies. This paper, however, focuses on presenting results to support safe disposal of spent fuel, plutonium and highlyenriched uranium in higher-strength rock.The results support a safety case assertion that post-closure criticality is of low likelihood and, if it was to occur, the consequences would be tolerable.

scholarly journals Consequence modelling of hypothetical post-closure criticality events for spent fuel disposal

2015 ◽  
Vol 79 (6) ◽  
pp. 1505-1513 ◽  
Author(s):  
R. M. Mason ◽  
J. K. Martin ◽  
P. N. Smith ◽  
R. J. Winsley
Keyword(s):  
International Studies ◽  
Quasi Steady State ◽  
Spent Fuel ◽  
Regulatory Requirement ◽  
Geological Disposal ◽  
Waste Package ◽  
Decay Heat ◽  
Disposal Facility ◽  
Safety Case ◽  
The Uk

AbstractIn support of the Radioactive Waste Management (RWM) safety case for a geological disposal facility (GDF) in the UK, there is a regulatory requirement to consider the likelihood and consequences of nuclear criticality. Waste packages are designed to ensure that criticality is not possible during the transport and operational phases of a GDF and for a significant period post-closure. However, over longer post-closure timescales, conditions in the GDF will evolve.For waste packages containing spent fuel, it can be shown that, under certain conditions, package flooding could result in a type of criticality event referred to as 'quasi-steady-state' (QSS). Although unlikely, this defines a 'what-if' scenario for understanding the potential consequences of post-closure criticality. This paper provides an overview of a methodology to understand QSS criticality and its application to a spent fuel waste package.The power of such a hypothetical criticality event is typically estimated to be a few kilowatts: comparable with international studies of similar systems and the decay heat for which waste packages are designed. This work has built confidence in the methodology and supports RWM's demonstration that post-closure criticality is not a significant concern.

scholarly journals Thermal dimensioning to determine acceptable waste package loading and spatial configurations of heat-generating waste packages

2015 ◽  
Vol 79 (6) ◽  
pp. 1625-1632 ◽  
Author(s):  
Simon Myers ◽  
David Holton ◽  
Andrew Hoch
Keyword(s):  
Radioactive Waste ◽  
Waste Management ◽  
High Heat ◽  
Spent Fuel ◽  
Geological Disposal ◽  
Waste Package ◽  
Thermal Limits ◽  
Disposal Facility ◽  
Wide Range ◽  
Spatial Configurations

AbstractHeat-generating waste provides a number of additional technical challenges over and above those associated with the disposal of ILW. A priority area of work for Radioactive Waste Management (RWM) concerns the effect of heat on the engineered barrier system, and how this may be mitigated through the management of heat (thermal dimensioning) in a UK Geological Disposal Facility (GDF). The objective of thermal dimensioning is to provide a strategy to enable acceptable waste package loading and spatial configurations of the packages to be determined in order to enable high-heat generating waste to be successfully disposed in a GDF. An early focus of the work has been to develop a thermal modelling tool to support analyses of different combinations of package assumptions and other GDF factors, such as spacing of those packages, to assess the compliance with thermal limits. The approach has a capability to investigate quickly and efficiently the implications of a wide range of disposal concepts for the storage of spent fuel/HLW and the dimensions of a GDF. This study describes the approach taken to undertaking this work, which has included a robust appraisal of the key data (and the associated uncertainty); recent thermal dimensioning analysis has been performed to identify constraints on those disposal concepts.

scholarly journals Development of a Generic Safety Narrative for a UK Geological Disposal Facility

2015 ◽  
Vol 79 (6) ◽  
pp. 1633-1640 ◽  
Author(s):  
L. Bailey
Keyword(s):  
Environmental Safety ◽  
System Safety ◽  
Geological Disposal ◽  
Disposal Facility ◽  
Safety Barriers ◽  
Safety Case ◽  
The Uk ◽  
Surface Environment

AbstractThe UK has published a generic Disposal System Safety Case for a geological disposal facility (NDA, 2010) and is planning to update this in 2016. However, it is a challenge to present a meaningful safety case when the location and hence the design of a geological disposal facility are not known. Consequently, this paper describes our aim to present a narrative, explaining how we can have confidence in the long-term safety of a geological disposal facility. This narrative is based on an understanding of the environmental safety functions of a geological disposal facility and the features, events and processes (FEPs) that support them. The highest level environmental safety functions required for a geological disposal facility are isolation and containment. By isolation we mean removal of the wastes from people and the surface environment. By containment we mean retaining the radioactivity from the wastes within various parts of the disposal facility for as long as required to achieve safety. Beneath these top-level environmental safety functions we have identified generic environmental safety functions associated with each of the key safety barriers within a geological disposal facility, namely: the wasteform, the container, the local buffer or backfill, the mass backfill (in the access tunnels and service ways), the plugs and seals and the geosphere. This paper discusses the application of environmental safety functions and FEPs to building a safety narrative and explains how it is proposed to use such an approach to develop a generic environmental safety case for the UK to provide confidence in the longterm safety of a geological disposal facility after it has been sealed and closed.

scholarly journals Preliminary modelling of radionuclide migration in the argillaceous sediments of the Sumer Formation (Northwestern Bulgaria)

2020 ◽  
Vol 49 (3) ◽  
pp. 13-18
Author(s):  
Dimitar Antonov ◽  
Madlena Tsvetkova ◽  
Doncho Karastanev
Keyword(s):  
Radioactive Waste Disposal ◽  
High Level Waste ◽  
Spent Fuel ◽  
Radionuclide Migration ◽  
Geological Disposal ◽  
Disposal Facility ◽  
Deep Geological Disposal ◽  
High Level ◽  
Host Rocks ◽  
Selection Of

In Bulgaria, from the preliminary analyses performed for site selection of deep geological disposal of high-level waste (HLW) and spent fuel (SF), it was concluded that the most promising host rocks are the argillaceous sediments of the Sumer Formation (Lower Cretaceous), situated in the Western Fore-Balkan Mts. The present paper aims to compare the transport of three major radionuclides from a hypothetical radioactive waste disposal facility, which incorporates an engineering barrier of bentonite into the argillaceous (marl) medium. The simulations were performed by using HYDRUS-1D computer programme. The results are used for a preliminary estimation of argillaceous sediments as a host rock for geological disposal of HLW.

Uranium-Series Studies in Bedrock for the Safety Case of Deep Geological Disposal of Spent Fuel

2008 ◽  
Author(s):  
Kari Rasilainen ◽  
Juhani Suksi ◽  
Petteri Pitkänen ◽  
Nuria Marcos ◽  
Torbjorn Carlsson
Keyword(s):  
Spent Fuel ◽  
Geological Disposal ◽  
Uranium Series ◽  
Deep Geological Disposal ◽  
Safety Case

Research and development for geological disposal of higher activity wastes: the role and expectations of the Environment Agency

2011 ◽  
Vol 75 (4) ◽  
pp. 2431-2437
Author(s):  
C. R. Cailes ◽  
I. Barraclough ◽  
R. E. Smith ◽  
G. Thomson
Keyword(s):  
Research And Development ◽  
Research Programme ◽  
Environmental Safety ◽  
Nuclear Industry ◽  
Geological Disposal ◽  
England And Wales ◽  
Disposal Facility ◽  
Safety Case ◽  
Environment Agency ◽  
Regulatory Decisions

AbstractThe Environment Agency is the environmental regulator for the nuclear industry in England and Wales. We aim to ensure that any future Geological Disposal Facility (GDF) will meet our standards for protecting people and the environment during development, operation and following closure. We shall only grant an environmental permit for such a facility if the GDF developer submits an Environmental Safety Case (ESC) to the Environment Agency demonstrating that the proposed GDF will meet our standards. The ESC should be based on sound science and supported by appropriate research and development. The Environment Agency undertakes its own research programme to inform its regulatory decisions.

Framework for an environmental safety case for geological disposal in the UK

2012 ◽  
Vol 76 (8) ◽  
pp. 3457-3464 ◽  
Author(s):  
M. J. Poole ◽  
R. Kowe
Keyword(s):  
Environmental Safety ◽  
Approval Process ◽  
Site Specific ◽  
Geological Disposal ◽  
Disposal Facility ◽  
Safety Case ◽  
The Uk ◽  
A Site

AbstractThe implementation of a geological disposal facility requires the demonstration of confidence that such a facility would be safe during both the operational period and in the long-term after the closure of such a facility. The generic environmental safety case described in this paper is the vehicle used to demonstrate an understanding of environmental safety. It will be used to prepare a site-specific environmental safety case in due course. The approach taken will be consistent with a staged development and approval process, as advocated by the environmental regulators.

Design Options for the UK’s ILW Geological Disposal Facility

2009 ◽  
Author(s):  
Tim Hicks ◽  
Matt White ◽  
Tamara Baldwin ◽  
Neil Chapman ◽  
Fiona Neall ◽  
...  
Keyword(s):  
Public Consultation ◽  
High Level Waste ◽  
Geological Environment ◽  
Spent Fuel ◽  
Geological Disposal ◽  
Disposal Facility ◽  
Wide Range ◽  
The Uk ◽  
High Level ◽  
Design Options

Over the last few years, a major national programme of public consultation has been under way in the UK resulting, in 2006, in the announcement by government of geological disposal as the most appropriate solution for the long-term management of the UK’s long-lived and higher-activity radioactive waste and the launch, in 2008, of an implementation programme. The approach being pursued is to solicit volunteer communities to host a geological disposal facility, which may contain not only intermediate-level waste (ILW) and some low-level waste (LLW), but also high-level waste (HLW), any spent fuel (SF) declared as waste, and potentially other materials that may be declared as waste. These wastes have different physical, chemical, thermal and radiological characteristics, and different concepts will be required to accommodate their disposal, potentially in a single facility. The volunteer approach means that the geological environment that might eventually emerge as the preferred location is not known at the outset. Indeed, the siting process may require evaluation of several different geological environments because the UK has rich geological variability for such a small landmass. Consequently, the Nuclear Decommissioning Authority (NDA), which is charged with designing, developing and implementing a geological disposal facility, has investigated facility designs that could be appropriate for a wide range of host rocks and geological environments. This paper presents the results of a project carried out on behalf of the NDA to collate and report information on concepts for the geological disposal of ILW/LLW; a separate project carried out a parallel evaluation of options for disposing of HLW and SF. Initially, the range of geological disposal facility design options available worldwide for the disposal of ILW/LLW was evaluated. Nine disposal concepts were identified and reviewed that would cater for any geological environment likely to arise in the UK. These concepts have different engineering and operational aspects. The appropriateness of each option for implementation in five different generic geological environments was assessed using expert judgement, with input from the NDA, consultants and the UK regulatory agencies. The paper presents a set of generic designs derived from the study and discusses the key issues that would need to be addressed should any of these designs be considered for implementation in specific geological environments in the UK. The findings of this work are intended to provide a resource to support comparisons of alternative disposal concepts and the identification of designs suitable for the disposal of UK ILW/LLW in different geological environments.

Building the Safety Case for a Disposal Facility for Spent Fuel, HLW and Long-lived ILW in Switzerland

2002 ◽  
Vol 713 ◽  
Author(s):  
Paul A. Smith ◽  
Piet Zuidema ◽  
Lawrence H. Johnson ◽  
Jürg W. Schneider ◽  
Peter Gribi
Keyword(s):  
Development Strategy ◽  
Current Understanding ◽  
Opalinus Clay ◽  
Safety Concept ◽  
Spent Fuel ◽  
Northern Switzerland ◽  
Disposal Facility ◽  
Wide Range ◽  
Geological Repository ◽  
Safety Case

ABSTRACTThis paper describes a generic methodology for building the safety case for a geological repository, which is currently being applied to a possible facility for spent fuel, vitrified highlevel waste and long-lived intermediate-level waste in the Opalinus Clay of Northern Switzerland. The methodology involves:1. the identification of certain basic disposal principles,2. the choice of a disposal system, via a flexible repository development strategy,3. the derivation of the system concept, based on current understanding of the phenomena that characterise, and may influence, the disposal system and its evolution,4. the derivation of a safety concept, based on reliable, well understood and effective pillars of safety,5. the illustration of the radiological consequences of the disposal system through the definition and analysis of a wide range of assessment cases, and6. the compilation of the arguments and analyses that constitute the safety case, as well as guidance for future stages of the repository programme. A range of measures, including audits, are used to promote completeness of the phenomena considered in the safety case, and to avoid inadvertent bias.

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