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:
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 scramming the reactor before SAFDLs are violated. An approved D&S stability LTS should be implemented. SAFDL requirements are specified in SRP Section 4.2, “Fuel System Design,” and SRP Section 4.4, “Thermal and Hydraulic Design.” 7. Detect and Suppress stability LTSs rely on calculations of the reduction in critical power ratio margin for oscillations of a given amplitude. The response to these D&S LTS hardware oscillations should be modeled by a series of likely oscillation-amplitude contours and randomly failed local power range monitor (LPRM) instruments. Delta CPR over Initial MCPR Versus Oscillation Magnitude (DIVOM) is a staff-reviewed and approved methodology documented in NEDO-32465A. 8. All stability LTS implementations should have backup options in case the licensing solution is declared inoperable. Technical specifications should require that the primary licensing solution be restored in a relatively short period (no longer than 120 days). Backup options in effect for short periods may rely on administrative controls and manual operator actions only if operator actions required to prevent SAFDL exceedences can be accomplished within the two minutes allowed for operator action in the demonstration calculations. Backup solution exclusion regions should be confirmed for specific cycles and specified in the core operating limits report (COLR). 9. A number of stability LTSs has been reviewed and approved by the staff. As reactor and fuel designs evolve, the industry may propose new stability LTSs. The following criteria judge the acceptability of new stability LTSs and facilitates meeting the requirements of GDC 20: A. The LTS should protect against SAFDL violations automatically. B. The LTS should demonstrate by analysis that either (i) the probability