Some existing radioactive materials not currently designated as wastes due to their potential economic value may be declared as waste in the future and thus may need to be managed through geological disposal.[36] Such items include spent fuel from UK nuclear reactors that is not already contracted for reprocessing; uranium and plutonium stocks from spent fuel reprocessing; uranium from fuel manufacturing; and non standard or ‘‘exotic’’ fuels from experimental and research reactors. These other potential wastes represent a significant increase in the activity for disposal. For example, as a result of past and currently planned reprocessing operations at Sellafield, the UK will have amassed approximately 100 tonnes of separated plutonium. Regardless of their eventual management route, these materials, in combination with the HLW discussed in section 2.1, represent exceptionally challenging wasteforms. For example, plutonium stocks potentially present major challenges for disposal due to both nuclear security and criticality issues. In addition, wastes from any new nuclear build and Ministry of Defence sources are also likely to be managed via geodisposal.1