International Nuclear Safety Categories (INSC) for LWRs

The paper presents safety categories for international light water reactors (LWRs) including Gen II, Gen III, Gen III.5, SMR, and SMP. They can be categorized up to 9 safety categories. Reactors in the same generation do not necessarily fall on the same safety category. For example, Gen III.5 reactors fall on safety categories 4, 5, 6 and 7 depending on their safety design characteristics. There is no single standard safety level for Gen III.5 reactors that is often called such as 'Gen III.5 safety'. Their safety levels differ from reactor to reactor. Moreover, there can be safety levels that excel existing Gen III.5 reactors. Gen IV excludes LWRs by the definition of GIF. Therefore, it is impossible to use 'Gen IV safety' to express safety level of LWRs. It is also unknown whether Gen IV reactors are truly safer than Gen III.5 reactors, yet. Therefore, generations are not precise enough to rank safety levels of different reactors correctly. It is necessary to discuss safety levels of different reactors with much higher resolution than generation. Safety categories 0 to 9 are developed mainly based on PSA insights and safety design characteristics. Some examples of reactors that fall on each safety category are provided. The paper also presents a new plant concept that applies to mid to 1600 MWe ABWR and is rated as safety category 5. (author)