UK's First Licensed MWB Package - M4/12 UFC MK-III

The NDA's programme of managing the UK's historic nuclear legacy includes the re-disposition and/or consolidation of fissile materials. The paper is based on a real project. This paper discusses aspects of legacy fuels which can be important to the transport criticality safety case and how they differ from fuels from thermal reactors. The legacy fuels are predominantly from experimental and/or fast reactors. The issues addressed include inventory determination and uncertainty, fuel damage from impact and corrosion and validation of the criticality calculations. Use of an existing previously licensed ‘conventional’ Single Water Barrier (SWB) package with modifications to enable a Multiple Water Barrier (MWB) design has been employed to transport the materials. This has involved extensive collaborative work from various organisations and disciplines to gain the UKs first MWB approved package. The criticality aspects of the MWB design are discussed.