Document: NUREG-0800
Document ID: ddaa3c7d-ce79-4a3f-aaae-4e4436ab7bc1
Document Type: srp
Title: NUCLEAR DESIGN
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070740003.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4.3
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s and data for the design calculations; uncertainty analyses and experimental comparisons presented for the design calculations; the sufficiency of design cases calculated covering times in cycle, rod positions, load-follow transients, etc.; and special problems such as power spikes due to densification, possible asymmetries, and misaligned rods. 4.3-9 Revision 3 - March 2007 B. A reasonable probability exists that in normal operation the design limits will not be exceeded, based on consideration of information received from the power distribution monitoring instrumentation; the processing of that information, including calculations involved in the processing; the requirements for periodic check measurements; the accuracy of design calculations used in developing correlations when primary variables are not directly measured; the uncertainty analyses for the information and processing system; and the instrumentation alarms for the limits of normal operation (e.g., offset limits, control bank limits) and for abnormal situations (e.g., tilt alarms for control rod misalignment). Criteria for acceptable values and uses of uncertainties in operation, instrumentation numerical requirements, limit settings for alarms or scram frequency and extent of power distribution measurements, and use of ex-core and in-core instruments and related correlations and limits for offsets and tilts, all vary with reactor type. They can be found in staff safety evaluation reports and in appropriate sections of the technical specifications and accompanying bases for reactors similar to the reactor under review. The organization responsible for the review/assessment of nuclear design has enunciated Branch Technical Position 4-1 for Westinghouse reactors that employ constant axial offset control. Acceptance criteria for power spike models can be found in a NUREG report on fuel densification, and are discussed in Regulatory Guide (RG) 1.126. Generally, special or newly emphasized problems related