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.

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.

scholarly journals Biosphere studies supporting the disposal system safety case in the UK

2012 ◽  
Vol 76 (8) ◽  
pp. 3225-3232 ◽  
Author(s):  
R. C. Walke ◽  
M. C. Thorne ◽  
S. Norris
Keyword(s):  
Global Climate ◽  
Radioactive Wastes ◽  
Catchment Scale ◽  
System Safety ◽  
Near Surface ◽  
Geological Disposal ◽  
Safety Case ◽  
The Uk ◽  
Long Timescales ◽  
Surface Environment

AbstractHigher activity radioactive wastes remain hazardous for extremely long timescales, of up to hundreds of thousands of years. Disposing of such wastes deep underground presents the internationally accepted best solution for isolating them from the surface environment on associated timescales. Geological disposal programmes need to assess potential releases from such facilities on long timescales to inform siting and design decisions and to help build confidence that they will provide an adequate degree of safety. Assessments of geological disposal include consideration of the wastes, the engineered facility, the host geology and the surface and near-surface environment including the biosphere. This paper presents an overview of recent post-closure biosphere assessment studies undertaken in support of the Nuclear Decommissioning Authority Radioactive Waste Management Directorate disposal system safety case for geological disposal of the United Kingdom's higher activity radioactive wastes. Recent biosphere studies have included: (1) ensuring that the United Kingdom's approach to consideration of the biosphere in safety case studies continues to be fit for purpose, irrespective of which site or sites are considered in the United Kingdom's geological disposal programme; (2) updating projections of global climate and sea level, together with consideration of the potential importance of transitions between climate states; (3) considering geosphere–biosphere interface issues and their representation, including redox modelling and catchment-scale hydrological modelling; and (4) identifying key radionuclides and developing a series of reports describing their behaviour in the biosphere together with an evaluation of associated implications for post-closure assessment calculations.

Durability of potential plutonium wasteforms under repository conditions

2012 ◽  
Vol 76 (8) ◽  
pp. 2911-2918 ◽  
Author(s):  
G. Deissmann ◽  
S. Neumeier ◽  
G. Modolo ◽  
D. Bosbach
Keyword(s):  
Chemical Reactivity ◽  
Final Decision ◽  
Geological Disposal ◽  
Aqueous Environments ◽  
Safety Case ◽  
Key Issues ◽  
The Uk ◽  
High Level ◽  
Radionuclide Release

AbstractSeparated stocks of UK civil plutonium are currently held as a zero value asset in storage, as there is no final decision about whether they should be treated as a resource for future use as nuclear fuel or as waste. Irrespective of future UK government strategies regarding plutonium, at least a portion of the UK civil plutonium inventory will be designated for geological disposal. In this context, we performed a high-level review of the performance of potential wasteforms for the disposal of separated civil plutonium. The key issues considered were the durability and chemical reactivity of the wasteforms in aqueous environments and the long-term radionuclide release under conditions relevant to geological disposal. The major findings of the review, relevant not only to the situation in the UK but to plutonium disposal in general, are summarized in this paper. The review showed that, in the event of a decision being taken to declare plutonium as a waste for disposal, more systematic studies would be required to constrain the wasteform performance under repository conditions in order to derive realistic source terms for a safety case.

An Assessment of the Radiological Impact of Human Intrusion at the UK Low Level Waste Repository (LLWR)

2011 ◽  
Author(s):  
Tim. Hicks ◽  
Tamara Baldwin ◽  
Richard Cummings ◽  
Trevor Sumerling
Keyword(s):  
Environmental Safety ◽  
Assessment Model ◽  
Disposal Site ◽  
Barrier Materials ◽  
Low Level ◽  
Geotechnical Investigations ◽  
Safety Case ◽  
Waste Repository ◽  
The Uk

The UK Low Level Waste Repository Ltd submitted an Environmental Safety Case for the disposal of low-level waste (LLW) to the Environment Agency on the 1st of May 2011. The Environmental Safety Case (ESC) presents a complete case for the environmental safety of the Low Level Waste Repository (LLWR) both during operations and in the long term (Cummings et al, in these proceedings). This includes an assessment of the long-term radiological safety of the facility, including an assessment of the potential consequences of human intrusion at the site. The human intrusion assessment is based on a cautiously realistic approach in defining intrusion cases and parameter values. A range of possible human intrusion events was considered based on present-day technologies and credible future uses of the site. This process resulted in the identification of geotechnical investigations, a housing development and a smallholding as requiring quantitative assessment. A particular feature of the site is that, because of its proximity to the coast and in view of expected global sea-level rise, it is vulnerable to coastal erosion. During such erosion, wastes and engineered barrier materials will be exposed, and could become targets for investigation or recovery. Therefore, human intrusion events have been included that are associated with such activities. A radiological assessment model has been developed to analyse the impacts of potential human intrusion at the site. A key feature of the model is the representation of the spatial layout of the disposal site, including the engineered cap design and the large-scale spatial heterogeneity of radionuclide concentrations within the repository. The model has been used to calculate the radiation dose to intruders and to others following intrusion at different times and at different locations across the site, for the each of the selected intrusion events, considering all relevant exposure modes. Potential doses due to radon and its daughters in buildings constructed on excavated spoil from the repository are a particular concern. Options for managing the emplacement of the radium-bearing waste packages with regard to human intrusion have been assessed. These calculations show that a managed waste emplacement strategy can ensure that calculated doses are consistent with regulatory guidance levels.

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.

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.

An overview of near-field evolution research in support of the UK geological disposal programme

2012 ◽  
Vol 76 (8) ◽  
pp. 2995-3001 ◽  
Author(s):  
T. M. Beattie ◽  
S. J. Williams
Keyword(s):  
Radioactive Waste ◽  
Host Rock ◽  
Near Field ◽  
Radioactive Decay ◽  
Geological Disposal ◽  
Nuclear Decommissioning ◽  
Disposal Facility ◽  
Engineered Barriers ◽  
The Uk

AbstractThe near field, together with the containment and isolation provided by the geosphere, contributes to the long-term safety provided by a geological disposal facility (GDF) after closure. The different engineered barriers can prevent or limit the release of radionuclides and their migration to the undisturbed host rock or geosphere and are expected to fulfil their post-closure safety functions for many thousands to hundreds of thousands of years. They will continue to contribute to containment after their eventual degradation when there would no longer be confidence that they would continue to fulfil all of their safety functions in their totality. By that time, significant radioactive decay will have occurred, substantially reducing the hazard associated with the wastes. Therefore, demonstration of long-term safety requires an understanding of the evolution of the engineered barriers and the consequences for the generic safety functions that the different barriers provide. This paper provides an overview of the research of the Nuclear Decommissioning Authority Radioactive Waste Management Directorate into the evolution of the near field of a GDF.

Developments in UK Regulation of Nuclear Wastes

2003 ◽  
Author(s):  
Stuart Newstead ◽  
Mick Bacon ◽  
Jim Cochrane
Keyword(s):  
Waste Management ◽  
Environmental Safety ◽  
Management Options ◽  
Regulatory Oversight ◽  
Nuclear Site ◽  
Management Plans ◽  
Safety Case ◽  
Environment Agency ◽  
The Uk

The UK has a significant nuclear legacy arising from Government funded work going back to the 1940s. Government is proposing radical changes to current arrangements to tackle this legacy, clean-up nuclear sites and develop its policy for managing solid radioactive waste. As part of these developments the Nuclear Installations Inspectorate of the Health & Safety Executive, the Scottish Environment Protection Agency and the Environment Agency are putting in place joint working arrangements to improve the regulation of intermediate level radioactive wastes (ILW). The aim is to ensure that ILW is managed in a sustainable way taking into account long-term environmental considerations. These arrangements provide for improved regulatory oversight of (i) proposals from nuclear site licensees to condition ILW, and (ii) the work by Nirex to develop further its phased disposal concept (PDC). The regulators will scrutinise: • ILW conditioning proposals: This involves assessing site waste management plans, waste management options (e.g. BPEO assessments), conceptual designs and functional specifications for waste conditioning plants, detailed designs, construction, commissioning and operation of the plants, and the state of waste packages. • Nirex’s on-going work: This involves examining Nirex’s PDC, its application to ILW conditioning proposals and associated Letters of Comfort/Letters of Advice (LoC/LoA) and the possible future development of an environmental safety case for an eventual repository. A description is given of the regulators’ process associated with these new arrangements.

Comparison of a post-closure transient criticality model with the Oklo natural reactors

2012 ◽  
Vol 76 (8) ◽  
pp. 3145-3153 ◽  
Author(s):  
R. M. Mason ◽  
J. K. Martin ◽  
P. N. Smith ◽  
B. D. Turland
Keyword(s):  
Steady State ◽  
Observational Evidence ◽  
Fissile Material ◽  
Quasi Steady State ◽  
Natural Analogue ◽  
System Safety ◽  
Geological Disposal ◽  
Disposal Facility ◽  
Safety Case ◽  
Modelling Approach

AbstractIn support of the disposal system safety case for a geological disposal facility (GDF) there is a requirement to consider 'what-if' hypothetical scenarios for post-closure nuclear criticality. Although all such scenarios are considered very unlikely, one 'what-if' scenario is the mobilization of fissile material from a number of waste packages and its slow accumulation within the GDF or the immediate surroundings. Should sufficient fissile material accumulate a quasi-steady-state (QSS) transient criticality event could result. A computer model has been developed to understand the evolution and consequences of such an event.Since a postulated QSS criticality could persist for many millennia, building confidence in the modelling approach is difficult. However, the Oklo natural reactors in Africa operated for similar durations around two billion years ago, providing a natural analogue for comparison. This paper describes the modelling approach, its application to hypothetical criticality events for a GDF, and how the model can be compared to Oklo. The model results are found to be in agreement with the observational evidence from Oklo, building confidence in the use of the QSS model to simulate postulated post-closure criticality events in GDFs.

scholarly journals Representation of estuarine, coastal and marine biosphere systems within post-closure performance assessments supporting geological disposal of higher activity radioactive wastes in the UK

2015 ◽  
Vol 79 (6) ◽  
pp. 1467-1474 ◽  
Author(s):  
R. C. Walke ◽  
M. C. Thorne ◽  
J. T. Smith ◽  
R. Kowe
Keyword(s):  
Sediment Accumulation ◽  
Radioactive Wastes ◽  
Performance Assessments ◽  
Geological Disposal ◽  
Marine Systems ◽  
Quantitative Evidence ◽  
Potential Contaminant ◽  
Estuarine Coastal ◽  
The Uk

AbstractRadioactive Waste Management Limited (RWM) is tasked with implementing geological disposal of the United Kingdom's (UK) higher activity radioactive wastes. This paper describes how RWM's biosphere modelling capability has been extended from a solely terrestrial model to allow potential contaminant releases to estuarine, coastal and marine systems around the UK to be represented. The new models aim to strike a balance between being as simple as can be justified, erring on the side of conservative estimates of potential doses, while also representing the features and processes required to reflect and distinguish UK coastal systems. Sediment dynamics (including meandering of estuaries and sediment accumulation) are explicitly represented in a simplified form that captures the accumulation and remobilization of radionuclides. Long-term transitions between biosphere systems (such as from a salt marsh to a terrestrial system) are outside the scope of the study. The models and supporting data draw on information about the UK that is representative of present-day conditions and represent potential exposures arising from both occupational and recreational habits.?Generic calculations demonstrate that potential doses to humans arising from releases to estuarine, coastal and marine systems are typically more than two orders of magnitude lower than those for equivalent releases to terrestrial systems via well water and groundwater discharge to soil. The extended capability (i) ensures that RWM is able to undertake assessments for potential coastal site contexts, if and when required, and (ii) provides RWM with quantitative evidence to support the principal focus on terrestrial releases ( particularly for more generic assessments).

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