Low Level Waste Repository at
Drigg, Cumbria, UK
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Halcrow has significant long-term experience of the design and safety issues associated with radio-active waste repositories. This experience is based on:
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A continuous involvement since 1993 with the Low Level Waste Repository (LLWR) for BNFL at Drigg |
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Design of nirex compliant, 3m3, stainless steel ILW drums capable of sustaining the stacking, seismic and impact loadcases that could be generated during the long term storage at various UK reactor sites and finally at the planned future national waste repository |
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Optimisation, outline design and public inquiry support for nirex, for the Sellafield deep waste repository |
Halcrow has all of the requisite skills to assist clients in the development, planning and design of existing and future repositories.
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An indication of the scope of our services is given in the case studies below:
case study
Low Level Waste Repository
at Drigg, Cumbria, UK
Halcrow has been continuously involved with Low Level Waste Repository (LLWR) at Drigg since 1993. The work has comprised numerous studies intended to support BNFL’s Operational Environmental Safety Case and Post-Closure Safety Case. These include:
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risk assessment |
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engineering performance studies |
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reviews and costings of design options |
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materials resources studies |
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geotechnical interpretation |
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development of a conceptual coastal change model |
Elements of the work which are ongoing or have been completed since 2002 are summarised below.
Support for the preparation of the LLWR Post-Closure Safety Case (1996 - 2003)
Halcrow assisted BNFL in several aspects of the development and documentation of the September 2002 LLWR Post-Closure Safety Case (PCSC). This involved preparing two of the PCSC reports that were issued to the Environment Agency in September 2002 and preparation of over 20 supporting documents. The work included:
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Preparing reviews of international practice in the design of radioactive waste disposal facilities, covering the approaches adopted worldwide for the disposal of intermediate and low-level waste and specifically dealing with international design practice for capping systems, cut-off walls and drainage systems. |
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Outline design of several of the proposed barrier and drainage components including the capping system, cut-off walls and leachate drainage. Modifications were also proposed to the design of the vaults and the trench disposal areas to improve the long-term performance of the closure system. |
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Design optimisation studies including evaluation of different types of bentonite enhanced soils for use in barrier components, and variants on cap geometry and cap construction. This work covered the very wide range of component performance and climatic conditions that could be anticipated during the life of the capping system (up to 10,000 years). |
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Estimation of construction costs for closure system components, including cut-off walls, deep drainage systems, capping systems, slope protection and coastal defences. |
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Reporting on the impact on the closure system of a wide range of possible future activities on the site, covering the potential radiological releases from the site resulting from future human actions, and other potentially disruptive events. |
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Assisting in developing a detailed FEP (Features, Events and Processes) list identifying the processes that could influence the long-term performance of the closure system. The system will include many components designed to work together to minimise radiological impact. These components are likely to respond differently to changes in the external environment and to the FEPs that will affect the repository over time. |
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Developing a methodology to look at the impact of the FEPs on the various components of the closure system. A risk-based approach used fault and event trees to identify and document fault sequences and other interactions that could affect closure system performance. |
Future Vaults (2002 – 2006)
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Halcrow has had a number of roles in the design development of the future vaults. This has included:
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Drigg and Sellafield - Conceptual coastal change projection model (1999 - 2006)
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| Drigg and Sellafield - Conceptual coastal change projection model |
Based on a review undertaken by Halcrow in 1999, it was concluded that the response of the coastline to past changes in sea level was complex and that a more detailed analysis of the historical evolution of the coastline was necessary. Halcrow was subsequently commissioned to develop a coastal database to include all historical topographic map data for the coastline, bathymetric surveys, selected aerial photograph coverage and other available spatial data. As part of this work, Halcrow undertook a detailed topographic and bathymetric survey of the coastline to establish an accurate baseline survey from which to assess past and future changes in coastline position, morphology and elevation. The survey of the coastal strip was undertaken using high-resolution digital aerial photography with integrated GPS and LiDAR.
Using the latest GIS technology these data were all spatially corrected to the Ordnance Survey grid projection to enable direct comparison of data sources. These data, together with information from the baseline survey of the area, have enabled a detailed assessment of changes in the coastline over the last 150 years.
Halcrow has been developing a conceptual coastal change projection model that will provide information on the coastline up to the next 10,000 years. The conceptual model uses a variety of quantitative and qualitative models to investigate the possible impact of different climate change scenarios on the open coast, barrier beaches and estuaries over a variety of timescales.
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