ML18153C834
| ML18153C834 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 12/02/1991 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-676, GL-88-14, NUDOCS 9112090272 | |
| Download: ML18153C834 (3) | |
Text
______ -__ -_ ------~------- ----
e e
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 December 2, 1991 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 Serial No.
NO/ETS Docket Nos.
License Nos.
SUPPLEMENTAL RESPONSE TO GENERIC LETTER 88-14 INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED SYSTEMS91-676 R2 50-280 50-281 DPR-32 DPR-37 By letter dated February 15, 1991, (Serial No. 88-578A) Virginia Electric and Power Company provided supplemental information regarding our actions pursuant to Generic Letter 88-14, Instrument Air Supply System Problems Affecting Safety-Related Equipment. In that letter we identified two issues for which we were experiencing difficulty in meeting the Instrument Society of America (ISA) Standard 7.3, Quality Standards for Instrument Air, 1981 revision. Specifically, reducing the particulate size to three microns in the Turbine Building and _Containment Instrument Air Systems and maintaining dew point at or below 35°F for the Containment Instrument Air System has not yet been accomplished.
As stated in our previous correspondence, the three micron particulate size will remain a long term goal for the Turbine Instrument Air System, although five microns will be used as the performance standard in the near term. As expected, the particulate
- content of the Turbine Building Instrument Air System continues to decrease at a gradual rate. Particulate counts at the five micron level are now near zero. Based on the results of performance testing conducted to date, it is expected that particulate cleanup in the Turbine Building Instrument Air System will extend over several operating cycles before the three micron standard is achieved.
The second issue of concern is the safety-related air-operated components inside containment that are supplied by the Containment Instrument Air System. The existing Containment Instrument Air System does not meet either the particulate standard or the dew point requirements of the ISA standard. However, the safety-related air-operated components remain operable. The Containment Instrument Air System is operated independently of the Turbine Building Instrument Air System and normally takes its suction directly from the containment atmosphere. The system can also take suction from outside the containment or be cross-connected to the Turbine Building
\\
Instrument Air System. However, when containment instrument air is supplied by the Turbine Building Instrument Air System or with the Containment Instrument Air l D
~i f
e compressors taking a suction from outside the containment, additional air mass will be added to the containment.
This additional air mass must be removed from containment, by the containment vacuum system, to maintain subatmospheric conditions.
A special test has been performed on each unit to evaluate the capability of the existing containment vacuum system to maintain the containment subatmospheric, using an instrument air source outside containment. The results of this special test were evaluated and it was determined that using outside Instrument Air Systems to supply containment air-operated components will require modification of the Containment Vacuum System and has the potential to significantly increase the offsite radiological gas releases (e.g., approximately 2 to 1 O times dependent on the modifications). Therefore, the appropriate course of action is to continue using the existing Containment Instrument Air System to supply the safety-related air-operated components in containment.
At present the existing Containment Instrument Air System uses refrigerant dryers that cannot meet the ISA Standard for dew point of 35°F. The minimum temperature in containment during operation is approximately 100°F and the dew point established by the dryers is approximately 50°F. However, due to the elevated containment temperatures during operation, the Instrument Air dew point temperature is maintained more than 18°F below containment ambient temperature, as required by the ISA Standard. Thus, with the elevated containment temperature during operation, dew point does not pose a component operability issue.
During Cold Shutdowns the safety-related air-operated components in containment will be supplied via the existing Turbine Building cross-connect, which meets the ISA Standard for a 35°F dew point.
Therefore, we are modifying our original response and will be taking an exception to the dew point and the particulate requirements of ISA-7.3, Quality Standards for the Containment Instrument Air System. Safety-related air-operated components have been maintained operable with the existing dew point and particulate size.
The Containment Instrument Air System is scheduled to be reviewed as part of the Reliability Centered Maintenance Program. Any additional maintenance, modification, or air quality requirements developed as part of this review will be evaluated and implemented as appropriate.
The Containment Instrument Air System and the safety-related air operated components will continue to be monitored and maintained in accordance with the preventive maintenance and testing programs implemented for the Generic Letter.
Please contact us if you have any questions.
Very truly yours,
!?Id~~
W. L. Stewart Senior Vice President - Nuclear
r *.
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