ML18039A661

Fpra FAQ 18-0014 - the Time to Detection Is Zero for Manual Non-Suppression Probability Calculations - Draft

ML18039A661
Person / Time
Issue date:	11/15/2017
From:	Office of Nuclear Reactor Regulation
To:	Cavedo R, Lindeman A, Pringle P Electric Power Research Institute, Exelon Corp
Wu A
Shared Package
ML18039A549	List: ML18039A624 ML18039A653 ML18039A661 ML18039A856 NUREG-2180, Data Collection in Support of Integrating Operating Experience Into NUREG-2180
References
FAQ 18-0014
Download: ML18039A661 (2)

Text

FAQ Number 18-0014 FAQ Revision 0 (Draft A)

FAQ Title The time to Detection is Zero for Manual Non-Suppression Probability (NSP) Calculations Plant: Various Date: November 15, 2017

Contact:

Robert Cavedo Phone: (301) 938-0397 Ashley Lindeman (704) 595-2538 Patricia Pringle (410) 495-4496 Email: Robert.cavedo@exeloncorp.com alindeman@epri.com patricia.pringle@exeloncorp.com Distribution: (NEI Internal Use)

FPRA TF BWROG PWROG Purpose of FAQ:

This FAQ provides an interpretation of when to begin crediting the empirically based manual Non-Suppression Probability (NSP) curves to align with the data used to develop the curves.

Relevant NRC document(s):

NUREG/CR-6850 NUREG/CR-6850 Supplement 1 (FAQ 08-0050)

NUREG 2169 Details:

NRC document needing interpretation (include document number and title, section, paragraph, and line numbers as applicable):

See list of relevant NRC documents Circumstances requiring interpretation or new guidance:

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.

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FAQ Number 18-0014 FAQ Revision 0 (Draft A)

FAQ Title The time to Detection is Zero for Manual Non-Suppression Probability (NSP) Calculations Detail contentious points if licensee and NRC have not reached consensus on the facts and circumstances:

None.

Potentially relevant existing FAQ numbers:

FAQ 08-0050, Manual Non-Suppression Probability Response Section:

Proposed resolution of FAQ and the basis for the proposal:

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.

If appropriate, provide proposed rewording of guidance for inclusion in the next Revision:

The following are proposed revisions to NUREG 2169:

The time of detection for manual NSP curves, Tdet, is considered zero (Tdet=0). The time of detection, Tdet , for other automatic suppression systems must still be calculated. Tdet=0 is only applicable to the empirically based manual NSP curves which already include the detection time in the data.

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