Session: 08-02: New Facility Planning/ Environmental Management (EM)/ Health & Safety

Paper Number: 110265

110265 - Development of the Monitoring Programme for Capping the United Kingdom Low Level Waste Repository. 

The United Kingdom Low Level Waste Repository has been in operation since 1959 and is operated by Nuclear Waste Services (NWS) on behalf of the Nuclear Decommissioning Authority. The original series of low level waste (LLW) disposal trenches have been superseded by vault disposals of containerised waste. Interim capping of the trenches was undertaken in 1986 and extended in 1997. Work on the construction of the final cap of the northern part of the trenches and Vault 8 is planned to commence in 2024.

NWS defines the objectives of its monitoring programme for the LLWR site to be:

·         to confirm that the repository system is not giving rise to unacceptable environmental hazards by direct measurement of the impacts and to ensure compliance with the relevant environmental standards;

·         to develop and build confidence in the models of the repository system by collecting data that may be used to refine conceptual models or in model parameterisation, calibration or validation;

·         to provide reassurance to stakeholders that the system is safe and is evolving in a manner consistent with the models and assumptions in the ESC;

·         to record baseline conditions before specific engineering developments or activities, such as the construction of a new repository component (for example, a vault) or the disposal of wastes at a particular location.

These form high-level monitoring objectives applicable throughout the period of authorisation of the site.

Capping of the repository is a significant development at the site and the environmental monitoring programme is being adapted to reflect the changes in engineering. Mapping of the required changes to the current groundwater, surface water and gas monitoring programme against the phased construction of the cap has been a significant undertaking. New monitoring points will be required in some areas where others will needed to be protected, extended or decommissioned at different stages of the construction work.

In addition, in order to minimise the long-term settlement of the cap the capping process is designed to surcharge the waste prior to construction of the final cap layers. New monitoring is required to:

·         Record leachate levels in the trenches underneath the surcharged material.

·         measure settlement of the existing trench cap during the placement of profiling fill and surcharge material.

·         record the behaviour of the containers during and post placement of material to form the final cap landform.

·         to enable the behaviour of the final cap during and following construction to be assessed.

Monitoring at the repository will continue to be adapted throughout the lifetime of the site to account for changes in the repository infrastructure (construction of the final cap, extension of the cut-off wall, future vaults etc). 

Presenting Author: James Champion Nuclear Waste Services

Presenting Author Biography: James is the Environmental Monitoring Manger at the UK LLW Repository having worked their since 2009.
He has worked on a number of nuclear licensed site and has been involved in environmental remediation programmes both in the UK and overseas.