Bob Vaughan, managing director at Croft Associates explains how a new generation of packaging for radioactive waste can save the industry billions of pounds...

Decommissioning is currently the key challenge for the nuclear industry, not least the high cost of retrieving, processing and packaging Intermediate Level Waste (ILW) waste.

There has been much debate about the long-term storage and transport of radioactive waste. Traditionally, nuclear sites have utilised unshielded containers for ILW with grouting of contents in complex encapsulation plants and storage in heavily shielded buildings. 

At the end of 2011 a significant change occurred with the issuing of the Nuclear Decommissioning Authority's (NDA) draft Integrated Waste Management Strategy Development Programme. This articulates the work required to develop an appropriate strategy, and for the first time it condoned the use of disposable robust self-shielding containers for the transport and final disposal of ILW.

This is a cautious, but important step forward. The industry has increasingly accepted that robust self-shielded containers manufactured in ductile cast iron (DCI) will help to accelerate site decommissioning and reduce costs by billions of pounds.

Why? Because the cost of constructing  shielded storage buildings and waste conditioning and grouting plant integral to waste packaging, is, by comparison with using  DCIs, very high and the approval process is very time consuming. The mechanical robustness offered by DCI obviates the need for waste conditioning and grouting to meet mechanical performance requirements.

DCI robust containers represent a new generation of designs that provide substantive technical benefits over earlier generation solutions that were heavily reliant on concrete for containment and shielding of radioactive waste.

Package manufacturers plan for ILW containers being stored for up to 150 years, and still being proven safe for handling and transport at the end of this period.

Designs that have been developed ensure that these requirements are met. Elastomeric-based sealing systems and DCI seal faces will degrade over time.  Seal systems which are testable, and if required can be replaced and retested without presenting the operators with a significant radiation hazard (the shielding is maintained in this operation), after extended storage, have been developed. 

The size of the container is also important.  ILW can be stored in any container as long as it meets safety, and, if relevant transport requirements, and if disposability is the end objective, the NDA RWMD disposability requirements.

The greater the capacity a container can provide, the more cost effective it is for the large quantities of waste that have to be managed.  It is simple economies of scale. DCI containers offer capacities of up to 40% more space for waste than equivalent concrete shielded containers.

The larger the capacity for waste the lower the cost per cubic metre of waste per container, which saves costs and operator dose through reduced waste conditioning, and reduces the effort in fitting large items into small volume containers,  providing for fewer handling and transport operations.

In our industry, where safety is paramount, change takes time. But  this new generation of packages will speed up  decommissioning , allowing for more rapid progress in hazard reduction, and reduce costs, plus the use of the new generation DCI robust packages  will ensure that  stringent safety requirements can be adhered to, not just now, but for centuries to come.

Bob Vaughan is managing director of Abingdon based radioactive waste packaging specialists, Croft Associates.

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