Categorization methods of nuclear materials used in advanced nuclear fuel cycles for physical protection systems

- Protection of nuclear materials needs categorization based on characteristics.
- Current categorizations are inconsistent for new types of materials.
- Influencing factors to material categorization methods are identified.
- Nuclear materials in pyroprocessing are tested for the current regulations.

The physical protection of nuclear materials is a significant regulatory requirement to prevent and impede the theft of materials suitable for nuclear explosives. These materials need to be systematically categorized based on their characteristics and risk. The categorization methods are evolving to reflect new issues. One of which is new types of materials from new technologies. We first reviews existing categorization methods for degrees of attractiveness, category levels, discount factor, physical barriers, chemical barriers, isotopic barriers, and radiological barriers. This paper tests the categorization methods for nuclear materials from pyroprocessing which converts spent oxide fuels to metallic forms and separates transuranic elements from fission products. TRU ingots from pyroprocessing are classified into Category I by all methods. However, several inconsistencies of categorization methods were found. The attractiveness level of TRU ingots can be differently interpreted as two different levels for some methods. For some materials, the application of radiological barriers results in different categories. Some approaches adopt multiple levels of radiological barriers for different capabilities of terrorists. Many methods evaluate materials as the current forms without considering the difficulty of separation, but a few methods consider chemical separation. Some methods exempt U ingots, but the others do not.