Often a design will require updating something in the UFSAR. It might be a drawing or some text. There’s a process for that . . . .
The UFSAR can be modified by following the process outlined in 10 CFR 50.59, but the Tech Specs cannot. The 50.59 process provides a graded approach to how much of a plant’s licensing basis can be changed by modifications before the NRC must grant permission to do so. Changes are allowed, for example, as long as they don’t result in more than a minimal increase in how frequently or how likely it is that an accident might occur, or as long as the modification doesn’t worsen the consequences of an accident. A change is prohibited from introducing the possibility of a new kind of accident that hasn’t yet been analyzed. There are other criteria, but these summarize the high points.
A plant will usually have two or three steps to follow when analyzing impacts to the licensing basis. There will usually be a 50.59 screening that’s performed to determine if the modification has any adverse impact to an SSC described in the LBDs. If the screening determines there isn’t, then the process ends there. If the modification “screens in,” then a full 50.59 evaluation is performed which examines the criteria discussed above (does the modification result in more than a minimal increase in frequency, likelihood, consequences, etc).