Innovative Waste Packaging and Associated Venting/Hydrogen Management

The original strategy for managing intermediate level waste (ILW) was developed in the 1980s by the UK Nuclear Industry Radioactive Waste Executive (NIREX), which is now the Radioactive Waste Management Limited (RWM), a wholly owned subsidiary of the Nuclear Decommissioning Authority (NDA). The strategy involved retrieving ILW, sorting and encapsulating it in cement based grout within thin walled stainless steel containers. The containers would then be transferred to a large purpose built shielded ILW store, where they would be stored until the planned deep geological disposal facility becomes available.In recognition of the high up-front costs of such a strategy, which requires remote facilities for the encapsulation and storage, and coupled with the long programme duration for the design, construction and commissioning of these facilities, waste management organisations responsible for managing the clean-up of legacy facilities within the UK have, in recent years, sought innovative solutions which could potentially accelerate clean-up and hazard reduction on sites, and with a lower overall programme lifecycle cost.Many of the recent innovative solutions are focused around a new family of packaging designs known as Robust Shielded Containers (RSCs). These are self-shielded containers manufactured from materials such as ductile cast iron or fabricated steel.The paper provides a high level overview of the generic concepts of RSCs developed by Croft and focuses on the specific challenges of wasteform evolution on waste package integrity and performance. In particular, the integrity and performance of the filtered vent system required to manage internal pressurisation and to ensure sufficient venting capacity of hydrogen and other evolved gases.The paper summarises the analysis by ARUP undertaken to substantiate the RSC integrity under detonation/deflagration explosion loadings arising from hydrogen accumulation. Analyses of the structural response of the filter assembly were undertaken for both detonation and deflagration explosion scenarios, with the loadings applied to the filter housing rim and to the filter vent cover.The paper also presents evidence of the mechanical performance of the filter medium in terms of pressure transients during deflagration events and the degree to which filtration efficiency is maintained.