Developing Hydrogeological Conceptual Models for a Nuclear Waste Disposal Site

Case Study

ESI has worked for many years on developing a hydrogeological conceptual model for a nuclear waste disposal site in Cumbria. An understanding of the site’s hydrogeology is required in order to support risk assessments which consider chemical and radiochemical contaminant transport within the groundwater system. The conceptual model was developed in conjunction with numerical groundwater flow and contaminant transport models and is regularly updated and refined. The conceptual model has been used to support two post- closure safety assessments and is currently being refined to support the next assessment.

 

ESI has been developing a hydrogeological conceptual model for a low-level waste disposal site in Cumbria, and has been carrying out this programme for many years. An understanding of the hydrogeology is required in order to support risk assessments which consider contaminant transport within the groundwater system.

 

The site has a large number of groundwater and surface water monitoring points and, prior to ESI’s involvement, many studies had been carried out at the site, both directly to support the hydrogeological understanding of the site and for research purposes. The first step in developing the conceptual model was to compile all this information. Data was entered into a custom-built database and reported through an electronic report management system. Following a review of this information, an initial conceptual model was developed which identified certain data gaps. A site investigation programme was then undertaken to acquire the necessary data and the conceptual model was refined.

 

The conceptual model was developed in conjunction with numerical groundwater flow and contaminant transport models. These models were built based on the conceptual model at the time and the results of the models have been used to help update and refine the conceptual model. In addition, further site investigations have been undertaken, often for geotechnical engineering purposes. The information from all of these studies, and from the site monitoring programme, have been fed into the conceptual model as a series of iterative updates.

 

The conceptual model has been used to support two post-closure safety assessments and is currently being refined to support the next assessment.