Document: NUREG-0800
Document ID: a7fafe76-5570-446b-96dd-3e53ec9bccb3
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340663.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4
CFR Part: 
CFR Title: 

Content:
ower maneuvers the total peaking factor, F , will not exceed the value consistent with the LOCA or other limiting acci~ent analysis. This operating 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 Fn (for LOCA) was 2.5 or greater. Later (late 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 spec- trum 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., 2200'F peak clad temperature) if F F 2 32. Also, Westinghouse showed that CAOC procedures employing a ± 5% targeq Eand would limit peak FQ for each of these reactors to less than 2.32. We recognized at that time, however, that not all plants needed to maintain F below 2.32 to meet FAC, or needed to operate within a i 5% band to achieve F F 2.32. In fact, Point Beach was allowed to operate with a wider band because the Wisconsin 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 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 i 5% band width we were approving, but the CAOC methodology. ThisQis 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