Quintessa

Decommissioning and Site Closure

AMBER has been used as an integrated site-wide performance assessment tool supporting strategic decisions about the decommissioning and closure of nuclear sites.

Models of initial contamination, subsequent contaminant migration and potential exposures help decision makers to understand the long-term implications of contamination and explore associated remediation options and strategies.

AMBER has been applied to long-term modelling of small rural communities after the Fukushima Daiichi nuclear power station accident, on behalf of JAEA. An AMBER model has been developed that enables a range of remediation options to be assessed for individual sites, based on measured levels of contamination, its distribution and patterns of land-use.

For Dounreay Site Restoration Limited (DSRL), AMBER was used to model the full range of potential sources of residual contamination that might remain at the site at closure, including authorised waste disposal facilities, contaminated land and sub-structures. A range of decommissioning and remediation options was assessed for each. The long-term modelling accounts for environmental change, including climate change, sea-level change and coastal erosion. The resulting tool enabled a range of different decommissioning scenarios to be assessed on an integrated, site-wide basis in support of site management plans.

Previously, DSRL have undertaken a project to isolate the D1225 Shaft, which contains intermediate level radioactive waste, from the surrounding groundwater by grouting fissures in the surrounding rock to form an impermeable curtain. DSRL is now working towards retrieving the 800 m3 of waste. As part of its support to this project, Quintessa produced a series of post-closure environmental safety cases, including supporting performance assessments for the shaft. The aim was to establish potential impacts from residual contamination to humans and the environment, as well as investigate the key features of the performance of the system, and explore the possible consequences of unlikely events.

Image copyright Dounreay Site Restoration Ltd and NDA.