What Is a “Known and Established” Standard?

The NRC staff, and licensees will sometimes cite a Known and Established Standard, especially when there is evidence that the staff’s position, with respect to a Known and Established Standard, may have changed. Licensees will often flag such changes as backfits, and demand that they meet the requirements of the Backfit Rule in the Code of Federal Regulations (10 CFR §50.109). However, the term, Known and Established Standard, is not clearly defined. If the term is not defined by the NRC staff, then it’s possible that it will be defined by others, most notably by licensees with technical issues or license amendment requests (LARs) that are undergoing the staff’s review. What follows is a discussion of the origin and application of the NRC’s Known and Established Standard, and how it might be defined. The Known and Established Standard is first deconstructed into its two components, Known and Established, and then each is defined separately. When this is done, it becomes apparent that some Known and Established Standards can be more important than others. The two definitions can be used, together, to distinguish between unequal, even incompatible Known and Established Standards. This could help the NRC staff identify the most relevant Known and Established Standard to apply in its review or evaluation of a particular technical issue or license amendment request (LAR). Simply choosing the most recent of Known and Established Standards might not be adequate.