Radiological Protection in Transporting Fissile Material within Refrigerated ISOs

The UK government has a strategic objective to consolidate fissile materials onto a single site. Our customer’s site inventory included unused, spent Fast Reactor fuel and an assortment of fissile material from other mainly UK/USA nuclear establishments originally received for reprocessing, and stranded by the closure of specialist facility in the 1990s.To enable the transport of significant quantities of material with a high risk of thermal degradation to packing materials, the material was transported in a temperature controlled environment to prevent material from degrading. The impact of degradation of an internal polyvinyl chloride (PVC) bag would not compromise safety or product quality during transport; however should the material degrade there would be a significant human impact due to additional reprocessing work requirements before final storage. The material was transported in a temperature controlled environment, maintaining a set temperature off -23ºC from packing at the consignor’s site until unpacking at the consignee’s site. To ensure the temperature controls were met during transport, strict controls were put in place, such that if PVC degradation was suspected, the consignee could plan mitigating actions. This was the first time International Nuclear Services (INS) had transported radioactive material within temperature controlled ISO containers, with this came new challenges and requirements to be met. Studies were undertaken proving that the increased requirements of the temperature controlled container systems resulted in the potential for employee dose limits to be breached. Ultimately, a hierarchy of controls were implemented to mitigate the risk of increased dose uptake during different stages of multimodal transport. This paper will detail the challenges faced with this novel method of transporting fissile material and how INS worked closely with stakeholders to complete the transport whilst ensuring dose uptake for employees was kept as low as reasonable practicable (ALARP) and compliant with regulations.