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.

Update on the Review of the LLWR 2011 Environmental Safety Case

2013 ◽  
Author(s):  
Richard Cummings ◽  
Amy Huntington ◽  
John Shevelan ◽  
Andrew J. Baker ◽  
Trevor Sumerling ◽  
...  
Keyword(s):  
Environmental Safety ◽  
Acceptance Criteria ◽  
Low Level ◽  
Additional Work ◽  
Local Stakeholders ◽  
Safety Case ◽  
Waste Repository ◽  
Environment Agency ◽  
The Uk

The UK Low Level Waste Repository has submitted a fully revised Environmental Safety Case (ESC) to the Environment Agency for the continued operation of the site. The Environment Agency is reviewing the submission. As part of the review of the ESC, we have been engaging with the Environment Agency to answer questions and provide further clarification where required. Once the review is complete, LLWR will apply for a revised permit for the continued operation of the site. We are required by our current Permit to operate the site in accordance with the assumptions of the ESC. We have developed a process for the implementation and maintenance of the ESC as a ‘live’ safety case under formal change control, and the development of waste acceptance arrangements identified as necessary to ensure that the repository is operated in a safe and optimised way, consistent with the assumptions and results of the ESC. Engagement with waste consignors has been essential in the development of revised waste acceptance criteria. Additional work has also been carried out in the development of an Article 37 submission, presenting the ESC to local stakeholders and developing of waste emplacement strategies.

Characterization and Assessment of the Groundwater Pathway for the Low Level Waste Repository, UK

2011 ◽  
Author(s):  
Lee J. Hartley ◽  
Martin James ◽  
Peter Jackson ◽  
Matt Couch ◽  
John Shevelan
Keyword(s):  
Radioactive Waste ◽  
Groundwater Flow ◽  
Environmental Safety ◽  
Long Term Evolution ◽  
Low Level ◽  
Term Evolution ◽  
Groundwater Flow Modelling ◽  
Safety Case ◽  
Waste Repository

The Low Level Waste Repository (LLWR) is the UK’s principal facility for the disposal of solid low-level radioactive waste and is operated by LLW Repository Limited. Presently, LLWR Ltd is establishing the long-term environmental safety of disposals of solid radioactive waste at the LLWR, through the submission of the 2011 Environmental Safety Case for the LLWR. This Environmental Safety Case addresses the Environment Agency Guidance on Requirements for Authorisation. Aspects of the submission consider improved vault design, closure design, and quantitative assessments. Each of these issues requires an understanding of the movement of water through the facility and the surrounding geology during operations and following facility closure. Groundwater flow modelling has been used extensively in support of the interpretation of field investigations, the development of the engineering design, and an assessment of the groundwater pathway as one of the major pathways by which contaminants may reach the environment. This paper describes these important aspects of the Environmental Safety Case. The geological environment in the region of the LLWR consists of Quaternary age deposits overlying older bedrock. The facility involves shallow excavations into the Quaternary deposits, originally for trenches, with disposals to a vault system beginning in 1988. In the post-closure phase these disposals are covered by a cap and surrounded by a cut-off wall to minimise the water flow around or through the waste. An innovative modelling methodology has been developed to represent the range of scales that have to be considered from the regional groundwater flow patterns over several kilometres, the scale of tens of metres around the immediate site area, and down to about 1 metre for details of flows within the repository itself in three dimensions. Detailed finite-element models of the flow through geological media and the engineered features are used to interpret site data and assess a credible set of post-closure situations and model cases. In the radiological assessment, a more simplified compartment model is used to assess uncertainties in hydrogeological properties and the long-term evolution of the engineered barriers. Together the approach provides flexible tools for understanding and assessing a comprehensive range of aspects including details of flows within the repository, dilution and migration in the external geology, the long-term evolution of the hydrogeological system, the implications of spatial variability and alternative geological models, and effects of uncertainties.

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.

Characterisation of the Geology of the UK Low Level Waste Repository

2011 ◽  
Author(s):  
John Shevelan ◽  
Nicholas T. Smith
Keyword(s):  
Site Investigation ◽  
Environmental Safety ◽  
Geological Model ◽  
Hydrogeological Model ◽  
Geological Interpretation ◽  
Low Level ◽  
Geological Models ◽  
Waste Repository ◽  
Site Characterisation ◽  
The Uk

The UK Low Level Waste Repository Ltd (LLWR) submitted an Environmental Safety Case (ESC) for the disposal of low-level waste (LLW) to the UK Environment Agency on the 1st of May 2011. As part of the ESC, the LLWR have to demonstrate that a programme of site investigation and site characterisation has been carried out to provide the requisite information for the ESC and support facility design and construction. This paper explains the development of the site investigation programme and how the understanding of the geology of the site has developed. The geological environment in the region of the LLWR consists of Quaternary age deposits overlying older bedrock. The site has been subjected to a series of site investigation programmes from 1939 to the present day. The development of 3-D geological models was necessary to integrate data from boreholes, trial pits, geophysical investigations and beach exposures and data gained from site operations. The understanding of the geology has developed with each new set of data. Early simple interpretations from a few boreholes have been superseded by a series of more complex interpretations each incorporating the increasingly detailed observations. Initial attempts to develop a lithostratigraphic representation of the geology proved difficult. It was also difficult provide a clear link between the geology and the hydrogeology using a lithostratigraphic approach as required for the development of hydrogeological models. A lithofacies approach to characterising the geology was adopted in 2007, which has allowed the grouping of geological units with similar hydraulic properties and the development of a regional 3-D geological model. The 3-D geological model has been used as the framework for the development of a hydrogeological model for the site. The development of the 3-D geological models has been iterative. It was observed that there are differences between models developed using solely mathematical interpolation and those controlled by geological interpretation. The different representations of the geological information have been used to consider the effects of uncertainty in the geological interpretation in the hydrogeological modelling.

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.

An Assessment of the Radiological Impact of Coastal Erosion of the UK Low-Level Waste Repository

2011 ◽  
Author(s):  
Trevor Sumerling ◽  
Paul Fish ◽  
George Towler ◽  
James Penfold ◽  
John Shevelan ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Erosion ◽  
Assessment Model ◽  
Coastal System ◽  
Future Evolution ◽  
Low Level ◽  
Waste Repository ◽  
The Uk ◽  
The Impact

The UK Low Level Waste Repository Ltd submitted an Environmental Safety Case for the disposal of low-level waste to our regulator, the Environment Agency, on the 1st of May 2011. This includes assessments of the long-term radiological safety of past and future disposals. A particular feature of the Low Level Waste Repository (LLWR) is that, because of its proximity to the coast, the site is vulnerable to coastal erosion. Our present understanding is that the site will be eroded on a timescale of a few hundred to a few thousand years, with consequent disruption of the repository, and dispersal of the wastes. We have undertaken a programme of scientific research and monitoring to characterise the evolution and function of the current coastal system that provides a basis for forecasting its future evolution. This has included modelling of contemporary hydrodynamics, geomorphological mapping, repeat LiDAR and aerial photographic surveys to detect patterns and rates of change, coastal inspections and reconstructions of post-glacial (i.e. last 15,000 years) sea levels and sediment budgets. Estimates of future sea-level rise have been derived from international sources and consideration given to the impact of such on the local coastline. Two alternative models of coastal recession have then been applied, one empirical and one physical-process based, taking account of the composition of Quaternary-age sediments between the coast and the site and uncertainties in future local sea level change. Comparison of the ranges of calculated times to site contact with sea-level rise indicate that the repository is most likely to be disrupted by undercutting of the engineered vaults and of the trenches. A novel and flexible radiological assessment model has been developed to analyse the impacts of the erosion of the repository and subsequent dispersal of wastes. The model represents the spatial layout of the site and distribution of radionuclides within the repository and is able to take account of a range of uncertainties. These include uncertainties related to the rate of erosion through the facility, amounts of co-erosion of geological and cap materials, alternative assumptions for residence of waste materials on the beach, alternative waste form associations, the wider dispersion of the eroded materials and marine sorption/desorption processes. Results indicate assessed annual doses and risks that are consistent with regulatory guidance levels.

Reuse of Low Specific Activity Material as Part of LLWR Design Optimisation

2013 ◽  
Author(s):  
Amy Huntington ◽  
Richard Cummings ◽  
John Shevelan ◽  
Trevor Sumerling ◽  
Andrew J. Baker
Keyword(s):  
Specific Activity ◽  
Environmental Safety ◽  
Management Approach ◽  
Low Level ◽  
Safety Case ◽  
Evaluation Stage ◽  
Potential Impact ◽  
And Control ◽  
Term Management

A final cap will be emplaced over the disposed waste as part of the closure engineering for the UK’s Low Level Waste Repository (LLWR). Additional profiling material will be required above the waste to obtain the required landform. Consideration has been given to the potential opportunity to reuse Low Specific Activity Material (LSAM, defined as up to 200 Bq g−1) imported from other sites as a component of the necessary profiling material for the final repository cap. Justification of such a strategy would ultimately require a demonstration that the solution is optimal with respect to other options for the long-term management of such materials. The proposal is currently at the initial evaluation stage and seeks to establish how LSAM reuse within the cap could be achieved within the framework of an optimised safety case for the LLWR, should such a management approach be pursued. The key considerations include the following: The LSAM must provide the same engineering function as the remainder of the profiling material. The cap design must ensure efficient leachate collection, drainage and control for Low Level Waste (LLW) (and, by extension, LSAM) during the Period of Authorisation. In the longer term the engineering design must passively direct any accumulating waters preferentially away from surface water systems. An initial design has been developed that would allow the placement of around 220,000m3 of LSAM. The potential impact of the proposal has been assessed against the current Environmental Safety Case.

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.

Research in support of the 2011 environmental safety case for the Low Level Waste Repository

2012 ◽  
Vol 76 (8) ◽  
pp. 3465-3474 ◽  
Author(s):  
A. Baker ◽  
R. Cummings
Keyword(s):  
Peer Review ◽  
Research Priorities ◽  
Research Programme ◽  
Environmental Safety ◽  
Group Key ◽  
Review Group ◽  
Safety Issues ◽  
Low Level ◽  
Safety Case ◽  
Waste Repository

AbstractThis paper provides a summary of the research programme undertaken in support of the Low Level Waste Repository's 2011 environmental safety case (ESC). The programme has been developed, based on an understanding of safety issues and the requirements of the ESC. The research requirements to underpin the safety case have been identified by means of an auditable process, and subjected to scrutiny by both the regulators and a peer review group. Key research priorities for the future are identified.

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.

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