05000423/LER-2007-003, Re Reactor Head Vent Valve Circuits Not Isolated from Control Room During Fire Scenario
| ML073381218 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/21/2007 |
| From: | Price J Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 07-0737 LER 07-003-00 | |
| Download: ML073381218 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 4232007003R00 - NRC Website | |
text
Dominion Nudear Connecticut, Inc.
D Millstone Power Station om inion Rope Ferry Road, Waterford, CT 06385 NOV 2 12007 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555
§Serial No.
MPS Lic/BAK Docket No.
License No.
07-0737 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2007-003-00. REACTOR HEAD VENT VALVE CIRCUITS NOT ISOLATED FROM CONTROL ROOM DURING FIRE SCENARIO This letter forwards Licensee Event Report (LER) 2007-003-00, documenting a condition identified at Millstone Power Station Unit 3, on September 27, 2007. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 50.73(a)(2)(ii)(B).
If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.
Sincerely, Si e/ice President - Millstone iI2Z~x&
Aim2
Serial No. 07-0737 Licensee Event Report 2007-003-00 Page 2 of 2 Attachments:
I Commitments made in this letter: None.
cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders - Project Manager U.S. Nuclear Regulatory Commission, Mail Stop 08 B3 One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No. 07-0737 Attachment I Licensee Event Report 2007-003-00 REACTOR HEAD VENT VALVES CIRCUITS NOT ISOLATED FROM CONTROL ROOM DURING FIRE SCENARIO MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)
Abstract
On September 27, 2007 at 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br /> while operating at 100% power, Millstone Power Station Unit 3 (MPS3) entered a Technical Specification (TS) Action Statement 3.3.3.5 for Remote Shutdown Instrumentation when a vulnerability in the fire safe shutdown strategy was identified affecting reactor vessel head vent valve transfer switches covered by TS 3.3.3.5. During an engineering review, it was discovered the control circuits for two reactor vessel head vent valves (3RCS*SV8095A, 3RCS*SV8096A) would not be properly isolated from the control room during certain fire scenarios.
Specifically, for catastrophic fires in the control room, cable spreading area or instrument rack room, operators evacuate the control room and control the plant from the Auxiliary Shutdown Panel (ASP) located in the east switchgear room.
During the review, it was discovered control circuit relays for 3RCS*SV8095A and 3RCS*SV8096A are located in the main control board. After the transfer switches on the Fire Transfer Switch Panel (FTSP),are repositioned to "Local,"
these control circuit relays, which are within the fire area, remain in the control circuit. Since these relays are located within the fire area, it must be assumed the fire can affect their function and thus could affect the transfer of control from the main control room to the ASP for 3RCS*SV8095A and 3RCS*SV8096A. Therefore, the transfer switches associated with these valves were declared inoperable.
This condition is being reported under 10CFR50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications," and under 10CFR50.73(a)(2)(ii)(B), "Any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety."
(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17) boration. Equipment required to maintain the plant in a stable long-term condition in Mode 3 would be unaffected under the postulated fire scenario. Additionally, there are multiple feed sources of water for long-term cooling. Given these multiple feed sources of water for cool down, the unit can remain in hot-standby for an extended period of time until the repairs can be made to restore letdown and commence emergency boration. Because the plant could safely achieve and maintain hot-standby until necessary repairs could be made to allow cool down to continue under this postulated condition, the control circuit routing had low safety consequences.
- 4.
Corrective Actions
Remote shutdown instrumentation transfer switch relays associated with the two reactor head vent valves (3RCS*SV8095A, 3RCS*SV8096A) were relocated from inside the Control Room to outside the postulated fire area.
The extent of condition was reviewed and no other similar conditions were found.
- 5.
Previous Occurrences
No previous similar events/conditions were identified.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].