Event Timeslots (1)

Day 2 – June 21
In 2012 the Nuclear Decommissioning Authority took the decision to cease the reprocessing of spent advanced gas-cooled reactor fuel with any remaining fuel and future arisings to be stored pending the final decision on whether to classify it as waste for disposal. Should the spent fuel be classified as waste it will be stored until the high heat generating portion of the UK’s geological disposal facility (GDF) is ready – this is expected to be in 2075.

Currently the strategy employed is long term wet storage with work being undertaken to support the alternative of dry storage with the work also being applicable for preparing for disposal. The aim of drying the spent fuel is to prevent the radiolysis of any water left in or on the pin which could lead to hydrogen and/or hydrogen peroxide being produced. These two radiolysis products are of particular concern due to hydrogen being explosive and hydrogen peroxide being corrosive. As the primary concern with extended wet storage is that water could seep through the cladding if it has failed. Stress corrosion cracking is being investigated as the likely cause of these failures which are often highly tortuous and branched cracks making characterisation difficult.

The work being carried out as part of this PhD aims to inform the drying process by producing a process model with this being split into two aspects. The experimental side is aiming to produce representative cracks in stainless steel in order to conduct drying trials which, in turn, can be used to validate the computational side of the work. On the computational side, a code has been written to determine the length and width of a crack which is required in order to produce an accurate model of the drying process. The current progress towards these goals will be discussed here.