Document: NUREG-0800
Document ID: a2d035da-992b-42e8-894f-787a019b437d
Document Type: srp
Title: NUCLEAR DESIGN
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070410.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4.3
CFR Part: 
CFR Title: 

Content:
rating scheme, called constant axial offset control (CAOC), involves maintaining the axial flux difference within a narrow tolerance band around a burnup-dependent target in an attempt to minimize the variation of the axial distribution of xenon during plant maneuvers. Originally (early 1974), the maximum allowable F (for LOCA) was 2.5 or greater. Later (late Q 1974), when needed changes were made to the ECCS evaluation model, Westinghouse, in order to meet physics analysis commitments to all its customers at virtually the same time, did a generic analysis (one designed to suit a spectrum of operating and soon-to-be-operating reactors) and showed that most plants could meet the requirements of Appendix K and 10 CFR 50.46 (i.e., 1204 C (2200 F) peak clad temperature) if F F< 2.32. Also, Westinghouse showed that 45 46 Q CAOC procedures employing a ± 5% target band would limit peak F for each of these reactors Q to less than 2.32. We recognized at that time, however, that not all plants needed to maintain F below 2.32 to Q meet fuel acceptance criteria (FAC) , or needed to operate within a ± 5% band to achieve F 47 Q F< 2.32. In fact, Point Beach was allowed to operate with a wider band because the Wisconsin 48 Electric Power Company demonstrated to our satisfaction that the reactors could be maneuvered within a wider band (+6,-9%) and still hold F below 2.32. We fully expected that in time most Q plants would have individual CAOC analyses and procedures tailored to the requirements of their plant-specific ECCS analyses. Therefore, when we accepted CAOC it was not just F = 2.32 and a ± 5% band width we were Q approving, but the CAOC methodology. This is analogous to our review and approval of ECCS and fuel performance evaluation models. The CAOC methodology, which is described in Reference 1, entails (1) establishing an envelope of allowed power shapes and power densities, (2) devising an operating strategy for the cycle which maximizes plant flexibility