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.

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.

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.

The Biogeochemical Transport Code Drink: a Mechanistic Description.

1994 ◽  
Vol 353 ◽  
Author(s):  
P. Humphreys ◽  
T. Johnstone ◽  
D. Trivedi ◽  
A. Hoffmann
Keyword(s):  
Finite Difference ◽  
Groundwater Flow ◽  
Transport Model ◽  
Long Term Evolution ◽  
Mineral Precipitation ◽  
Transport Code ◽  
Term Evolution ◽  
Uranium Migration ◽  
Geochemical Transport

AbstractDrinkis a 2D research code, which simulates the long term evolution of shallow, trenched, LLW disposal sites with significant groundwater flow. It employs a finite difference solver and is built around a geochemical transport model into which various functional units are interfaced. These units describe sorption, corrosion, microbiology, radionuclide decay, colloids, mineral precipitation and dissolution and gaseous release. Each of these units is described here, along with a 1 D simulation of uranium migration.

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.

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