ML17340B104
| ML17340B104 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute |
| Issue date: | 12/13/2017 |
| From: | Cavedo R Exelon Generation Co, Nuclear Energy Institute |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17340B096 | List: |
| References | |
| Download: ML17340B104 (8) | |
Text
Time of Detection Should be Zero for Manual Non-Suppression Likelihoods Rob Cavedo
Potential Realism Improvement Time of Detection should be Zero for Manual Non-Suppression Likelihoods 1
The guidance in NUREG/CR-6850 Appendix P implicitly and through example directs that the detection time be subtracted from the overall time until target damage when developing the manual non-suppression probability.
Although NUREG/CR-6850 Supplement 1 (FAQ 08-0050) and NUREG 2169 remove the brigade response time from the NUREG/CR-6850 approach, the subtraction term for the detection time remains.
As a result, the risk associated with the manual non-suppression probability is artificially high.
Identification of Relevant Guidance Time of Detection should be Zero for Manual Non-Suppression Likelihoods 2
NUREG/CR-6850 Appendix P (pg. 8-10)
Proposed Approach to Enhance Realism Time of Detection should be Zero for Manual Non-Suppression Likelihoods 3
The manual non-suppression probability (NSP) curves by nature of the data collection process already include the detection time in addition to the brigade response time.
Once a fire event is logged in a Nuclear power plant, it is detected.
NUREG-2169 used the Updated Fire Events Database (EPRI 1025284) in the development of the NSP curves. Whether the fire is detected by a detector, plant equipment failure, or personnel, the T=0 from which the fire is detected is inherently included in the manual response time curves.
Proposed Approach to Enhance Realism - Limitation Time of Detection should be Zero for Manual Non-Suppression Likelihoods 4
The Tdet=0 is ONLY applicable to manual NSP evaluations.
The time of detection must still be developed for automatic systems.
Example Time of Detection should be Zero for Manual Non-Suppression Likelihoods 5
When crediting the manual suppression likelihood Tdet=0.
Industry Benefit Moving towards more Realistic Cabinet Damage 6
This was not calculated during the October 2017 Workshop.
But considering an improvement to the NSP for electrical cabinets, this may result in a 5% reduction in CDF/LERF risk.
Questions Moving towards more Realistic Cabinet Damage 7