The D1225 intermediate-level radioactive waste (ILW) Shaft at Dounreay (“the Shaft”) was excavated in the 1950s. It is a vertical Shaft, located within a few tens of metres of the foreshore, having an average diameter of 4.6 metres (15 feet) and a total depth of 65.4 metres (215 feet). The Shaft received authorisation as a waste disposal facility in 1959. The majority of the waste in the Shaft was deposited between 1960 and 1971. A boot-shaped ring of grout (the hydraulic isolation barrier) was placed around the Shaft to control inflow of groundwater in 2007. NRS Dounreay are currently undertaking complex preparatory works to facilitate retrieval of the waste from the Shaft.

The conceptual site model (CSM) for the D1225 Shaft had last been updated by Quintessa in 2008 in parallel with the installation of the hydraulic isolation barrier. In 2022, Quintessa conducted a review of the geological, hydrogeological and hydrogeochemistry information that had become available since 2008. The review was used to underpin an updated CSM for presentation to the Scottish Environment Protection Agency (SEPA) to provide confidence that the hydraulic isolation barrier is performing well and in line with expectations.

Our specialists are now continuing to work with NRS Dounreay to develop a robust and optimised groundwater monitoring strategy which will provide long term and reliable data which are required to assess the impacts of waste retrievals and future closure of the Shaft. The strategy has been derived using a framework of strategic and technical objectives to ensure that future investment in the Shaft monitoring network is optimised and the value of existing groundwater monitoring facilities is maximised.

Image courtesy of Paul Wordingham, used (rescaled only) under the terms of a CC BY 2.0 licence.