Managing Voidage in a GDF: Towards a Methodology for Evaluating Voidage in Waste Packaging Proposals

Radioactive Waste Management Limited (RWM) is undertaking a multi-year programme of work to consider the implications of voidage for the post-closure safety of a geological disposal facility (GDF) for higher activity waste.

Wastes are being packaged for disposal in the UK now, and RWM provides advice to waste packagers regarding how waste can be packaged such that it is in a form that is compatible with a range of UK-relevant geologies that could in due course be selected to host a GDF. The disposability assessment process currently seeks to minimise voidage in waste packages, with the associated intent to minimise any potential impacts for GDF performance. Voidage in a waste package is defined as the macroscopic open space present in the package at the time of emplacement in a GDF, plus macroscopic open space that may develop as the package evolves during the post closure period.

The latest programme report, ‘Managing Voidage in a GDF: Towards a Methodology for Evaluating Voidage in Waste Packaging Proposals’ has just been completed. The associated work has involved improving understanding of the implications of voidage for the long-term mechanical evolution and performance of a GDF, developing a methodology for evaluating the extent of in-package voidage and its significance for post-closure safety, and applying the methodology to two worked examples. It has also involved reviewing and updating the voidage screening levels previously proposed.

In light of the work, RWM will be reviewing its approach to assessing voidage in the disposability assessment process, and the need to update guidance for waste producers.