ML18153C715
| ML18153C715 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 08/28/1991 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-376, NUDOCS 9109030262 | |
| Download: ML18153C715 (4) | |
Text
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 August 28, l99l United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION TECHNICAL SPECIFICATION CHANGE REQUEST SURVEILLANCE REQUIREMENTS IN THE EVENT OF INOPERABLE FIRE DETECTORS IN CONTAINMENT Serial No.
NO/ETS R2 Docket Nos.
License Nos.91-376 50-280 50-281 DPR-32 DPR-37 In accordance with your request of June 21, 1991, for additional information, we are submitting the following responses in support of your review of our proposed change request to Technical Specification 3.21.B.1 on surveillance requirements in the event of inoperable fire detectors in containment. Attachment 1 contains the requested information.
If you have any additional questions, please contact us.
Very truly yours, qv.~
\\in-W. L. Stewart Senior Vice President - Nuclear Attachments cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station
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e ATTACHMENT 1 SURRY POWER STATION UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION TECHNICAL SPECIFICATION CHANGE REQUEST INOPERABLE FIRE DETECTION INSTRUMENTS
e p 1 of 2 QUESTION Provide the location of the resistance temperature detectors (RTDs) in relation to the fire detectors.
RESPONSE
Existing smoke and heat detectors are installed on each reactor coolant pump, in the containment air system ducts, and in the cable penetration area. The locations listed below have RTDs to provide temperature monitoring for the same general area within containment as the existing fire detectors. These RTDs would be available as as alternate means of fire detection if the smoke and/or heat detectors in the affected area were to become inoperable. At a minimum, one RTD will be monitored in the affected area when the associated fire detection equipment is inoperable.
Containment dome Annulus area, approximate elevation 72' Annulus, approximate elevation 21 ', cable penetration area Pump cubicles, approximate elevation 18' QUESTION The response of the RTDs to a fire in containment is different from the response of fire detectors. We are concerned that the RTDs will not respond to smoke,ind provide early warning of a fire in these areas. This could affect a timely response to the detection of an actual fire inside containment. In order to properly evaluate your request, please justify how the containment RTDs will provide an equivalent level of detection to that provided by the normal fire detection system.
RESPONSE
Under normal operating conditions, the RTDs are used to monitor containment temperature. The average containment temperature is derived from a weighted average of the RTDs in the plant computer. A deviation alarm is initiated if the RTD temperature goes outside a predetermined range. At that time the RTDs can be individually read out from the computer for an assessment of local temperature.
For fire detection purposes, the RTDs will be monitored individually for temperature rise. It is necessary to monitor the RTDs individually since a fire inside containment would probably be small due to the limited amount of combustible material. Also, due to the large open nature of the containment, heat from the fire would rise toward the dome and be diluted by the large volume of cooler air. Therefore, if any one of the individually monitored RTDs shows a significant temperature rise above ambient conditions, a fire watch patrol will be dispatched for further assessment.
p 2 of 2 Using RTDs as an alternate means of fire detection in the containment is reasonable since there are several administrative and design features which limit the the risk of a fire in containment.
Fixed combustibles inside containment are limited per our Appendix R Program. Administrative controls require that transient combustibles be removed from the containment during operation. Also, limited welding and construction activities are allowed inside containment during power operations.
Finally, the Surry containment is operated at subatmospheric conditions during operation which reduces the risk and severity of fires by limiting the oxygen available for combustion.
QUESTION A determination on RTD operability is not addressed in the Technical Specification action statement.
RESPONSE
As noted above, the RTDs are used to monitor containment temperature. The average containment temperature is derived from a weighted average of the RTDs in the plant computer. A deviation alarm is initiated if the RTDs temperature goes outside a predetermined range. At that time the RTDs can be individually read out from the computer and a determination of operability can be made. The RTDs would be used as an alternate method in place of the existing fire detection instruments. If the RTD for the affected area was inoperable/unavailable as a backup instrument, a fire watch patrol would be established for the affected area and containment entries made on an eight hour basis as required by the Technical Specifications.