Costing | Radwaste

Modelling the cost of the UK geological repository

1 November 2011

A software model designed to estimate the cost of building and operating a geological repository for high-activity radwaste allows creation of multiple scenarios through manipulation of key variables of location, geology, volume of waste, type of waste, engineering layout and schedule.

The Nuclear Decommissioning Authority is responsible for planning and implementing geological disposal of radioactive waste in the UK. The work is being undertaken within NDA’s Radioactive Waste Management Directorate (RWMD).

RWMD need to evaluate the potential cost of the programme. The cost is affected by many factors, but the most significant are the inventory of waste, the timing of waste arisings, the timing and duration of each phase of implementation, the geology at the site in question and the design of the geological disposal facility itself. At this early stage of the programme, there are inevitable uncertainties about all of these factors; RWMD needed a tool to identify the cost impact of various options.

Engineering firm MWH worked with the RWMD to provide this. MWH gathered expert cost estimators, engineers, geologists and nuclear waste specialists for participation in several workshops, from both MWH offices and the RWMD.

A parametric cost model was developed to provide high-level estimates of the cost of a geological disposal facility in the UK mainland based on selecting certain parameters. It could also be used to identify the impact of changing parameters in the development of the base cost.

The fundamental assumption inherent in the cost model was that it would be possible to build whatever combinations of parameters were selected and that any subsequent solution could be safely operated and closed. The team developed the model on the understanding that the ability to select a combination of parameters should not be taken as proof that such a combination exists in practise.

Each scenario cost was produced by working through a series of screens inputting data, answering questions or selecting from various drop-down options.

Although there were many variables that could potentially impact on GDF costs, the parametric cost model included only those judged to be the most cost-significant: location, geology, volume of waste, type of waste, engineering layout and schedule. MWH recognised that particular parameters interact with each other. For example, the selection of a certain type of rock and the depth of the geological disposal facility has an impact on the engineering layout. This is because of the type of emplacement design that could be constructed. Alternatively the amount of waste assumed to be disposed of in the GDF would impact on the number of operational years required.

MWH tested, validated and benchmarked both its methodology and source data during development and after handover to RWMD. The calculations also have been verified by changing the parameters to mimic some of the global disposal facilities currently under consideration elsewhere in the world.

The model estimates that the cost of geological disposal of the UK’s radioactive waste is circa £12 billion (undiscounted) over 100 years. If separated uranium and plutonium were to be included the costs rise by £2 billion. The estimated cost to first waste emplacement is circa £4 billion. These costs do not include any waste from any new nuclear power stations.

Author Info:

Simon Bimpson, MWH director of programmes

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