Document: NUREG-0800
Document ID: f813a982-efc9-4295-a0ff-eb6a289f39ba
Document Type: srp
Title: BOILING WATER REACTOR STABILITY
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550017.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.9
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Content:
onditions are proposed) and for anticipated operational occurrences (AOOs). 2. If potential oscillations cannot be eliminated, design proposals should detect and suppress them reliably and readily. 3. Methodologies for resolving BWR density-wave stability issues are presented in the BWR Owners’ Group topical report NEDO-31960 along with Supplement 1 and were approved by the NRC in Reference 2. These reports provide LTSs to BWR stability issues as well as methodologies developed to support the design of systems needed for plants to comply with GDCs 10 and 12. 4. A reactor is considered stable if it satisfies one of the following criteria: A. The calculated decay ratio (DR) for all three common stability modes (core-wide, regional, and channel) satisfies the relationship DR < (1 - σ) where σ is the uncertainty of the calculation. Staff review and approve both the calculation methodology and its uncertainty. The value of σ is typically 0.2 but is methodology-dependent. This value includes the code uncertainty and some degree of variability of the input parameters. 15.9-4 March 2007 B. Use of an approved correlation to estimate the stability of the regional stability mode based on calculated core-wide and channel DRs is permitted. One example is the FABLE/BYPSS Stability Criteria reviewed and approved by staff and documented in NEDO-31960. 5. An acceptable LTS methodology to satisfy GDC 12 reduces the operating domain by defining an exclusion region where the reactor is not allowed to operate. The exclusion region, defined by the area in the operating map where stability criteria are not met, should be enforced automatically with an approved stability LTS. In addition to the exclusion region, the LTS defines a larger buffer region enforced with administrative controls. The buffer region minimizes challenges to the reactor protection system. 6. An alternative acceptable LTS methodology to satisfy GDC 12 will readily detect and suppress unstable power oscillations by