ML20006A136
| ML20006A136 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/11/1990 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 1744, NUDOCS 9001250264 | |
| Download: ML20006A136 (4) | |
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TOLEDO L
EDISDN-A Centenor Ener0Y company DONALD C. SHELTON
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Docket Number ~50-346 License Number NPF-3 Serial Number 1744 January 11, 1990 United States Nuclear Regulatory Commission Document Control Desk Vashington, D. C. 20555
Subject:
Summary of November 21, 1989 Meeting Concerning Removal'of Power =from Containment Emergency Sump Recirculation Valves DH-9A and DH-9B-Gentlemen:
On November 21, 1989, Toledo Edison (TE) and Nuclear Regulatory Commission-(NRC) Staff personnel met in NRC's White Flint offices in Rockville;_ Maryland-to discuss the removal of power from valves _DH-9A and DH-9B at the Davis-Besse Nuclear Power Station. These valves are the Containment Emergency Sump recirculation valves. Removal of power would_be accomplished by opening the valve operators' breakers at their respective motor control centers-(MCCs)
-prior to entering Mode 4 (Hot Shutdown) during plant startup and power ascension. Meeting attendees are listed in Attachment 1.to'this: letter.
Valves DH-9A and DR-9B are only utilized during a Loss of Coolant Accident (LOCA) and are closed during normal plant operation. The valves are interlocked with the Borated Vater Storage Tank (BVST)-outlet valves DH-7A and~
DH-7B (open during normal plant operation),.respectively,'to. preclude the simultaneous opening of one or both sets of valves which could cause-the draining of the BVST to the Containment Emergency Sump._ Valves'DH-9A and DH-9B receive a Safety Feature Actuation System (SFAS) signal to ensure-closure (for Containment isolation) on lov Reactor Coolant System pressure or high Containment pressure following a LOCA-and, at the same time, DH-7A and DH-7B receive the SFAS' signal to ensure opening and BVST alignment for safety injection. When the BVST reaches the low-low level (8 feet), a permissive signal is generated to allow blocking the-SFAS signal to DH-7A, DH-7B, Dil-9A and DH-9B, so that a manual opening of DH-9A and/or DH-9B can be accomplished in conjunction with the simultaneous closing of DH-7A and/or DH-7B to effect the recirculation mode of' safety injection.
During review of Control Room fire scenarios in accordance with 10CFR50,.
Appendix R, it was determined that a single isolated fire in the Control Room THF Tnt EDO EDIGON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652 J\\
9001250264 900111 PDR ADOCK 05000346 P
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D:ckot Nu2bar 50-346 License Number NPF-3 Serial Number 1744 Page 2 panels could cause spurious opening of DH-9A or DH-9B and result in draining i
the BWST to the Containment Emergency Sump. With the contents of the BVST in the Containment Emergency Sump, the BVST vater vould not be available to proceed with a normal shutdown of the plant.
(It is not necessary to postulate a LOCA in conjunction with a fire, therefore the safety systems necessary for mitigation of a LOCA but not necessary for normal shutdown of the plant are not required to be protected from a fire.) Four alternatives in lieu of removing power from DH-9A and DH-9B, vere investigated by TE to eliminate this coacern and are itemizcd as follows:
1)
Install a switch for.each valve in Control Room to effect power removal.
(This option is subject to the same fire induced failure and vill not alleviate the spurious opening of DH-9A or DH-9B in the event of a Control Room fire or a fire at the respective valve's HCC.)
2)
Install dual starters for the valve operators.
(This option, while providing adequate circuit separation in some plant areas, may still result in the postulated spurious opening of DH-9A or DH-9B due to a fire in the Control Room.).
3)
Install check valves in the Containment Emergency Sump recirculation lines to prevent draining of the. BUST to the Containment Emergency Sump.
(This option was rejected in that installation of a check valve vould adversely affect Low Pressure Injection Pump net positive suction head (NPSH) requirements, and very limited space is available for installation.)
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4)
Obtain an exemption to 10CFR50, Appendix R separation requirements for fires in the Control Room.
(This option would not be acceptable j
to the NRC Staff, as indicated by the NRC Fire Protection' Staff reviewer, and is inconsistent with the overall approach used to analyze Appendix R separation at the Davis-Besse Nuclear Power Station.)
Based on the above, removing power from DH-9A and DH-9B during normal operation was chosen as the logical alternative and would be accomplished by opening the valve operators' breakers at their respective MCCs. This requires manual action outside of the Control' Room during LOCA to close the valve operator's breaker at their respective.MCC's.
The acceptability of this approach is based on the following:
1)
The need to open DH-9A and/or DH-9B during a LOCA does not occur for at least 30 minutes post-LOCA.
2)
Upon completion of a modification, the MCC locations for the valve operators vill be in areas which can be accessed within the necessary l.
time.following the accident, and would not be prohibited by
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radiological conditions which may be produced during LOCA.
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Dockat Nu;ber 50-346-License Number NPF-3 Serial' Number 1744 Page 3 3)
Minimal operator action outside-of the Control Room is required during the first hour post-LOCA and sufficient personnel are
'available on shift to accomplish these tasks.
Emergency procedures-
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will specify that prior to transferring pump suction from the BVST to the Containment Emergency Sump, the valve operator circuit breakers must be closed locally at the McCs.
n During the meeting, the removal of power from DH-9A and DH-9B was appraised by
- NRC Staff to be acceptable based on the presented justification.
It.vas
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recommended that the requirement for power being removed from DH-9A and DH-9B during Modes 1, 2.-3 and 4 be noted in the Davis-Besse Nuclear Power Station Technical Specifications. Toledo Edison agreed'to provide a proposed Technical Specification change incorporating this recommendation, but that the proposed change was not required.to be submitted prior to effecting removal.of power from DH-9A and DH-9B.
If you have any questions concerning the above, please contact Mr. R. V. Schrauder, Manager - Nuclear Licensing, (419) 249-2366.
Very truly yours,
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RMC/ssg Attachment cc P. M. Byron, DB-1 NRC~ Senior Resident Inspector A. B. Davis, Regional Administrator, NRC Region III D. J. Kubicki, NRR Fire Protection Staff Reviewer T. V. Vambach, DB-1 NRC Senior Project Manager t
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Dockst Nu2bar 50-346 License Number NPF-3
. Serial Number 1744 Page.4 l
-Attachment 1 Removal of Power from DH-9A and DH-9B l
November 21, 1989 Meeting Attendees l
Nuclear Regulatory Commission T. V. Vambach - Senior Project Manager, DB-1 R. C. Jones - Branch Chief, Reactor Systems Branch
-Y. Gene Hsil - Reactor Systems Branch D. J. Kubicki - Fire Protection Staff Reviewer Toledo Edison D. R. Vuokko - Regulatory Affairs Supervisor K. C. Prasad - Nuclear Engineering Manager C. A. Hengge - Fire Protection Compliance Supervisor L. D. Young - Fire Protection-Engineer R. M. Cook - Licensing Engineer a.
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