ML13317B172

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Responds to Generic Ltr 88-14, Instrument Air Supply Sys Problems Affecting Safety-Related Equipment. Instrument Air Quality Assessed & Concluded to Be Acceptable
ML13317B172
Person / Time
Site: San Onofre Southern California Edison icon.png
Issue date: 08/30/1990
From: Nandy F
SOUTHERN CALIFORNIA EDISON CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-88-14, NUDOCS 9009070094
Download: ML13317B172 (5)


Text

Southern Caifornia Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 August 30, 1990 F. R. NANDY TELEPHONE MANAGER. NUCLEAR LICENSING (714) 587-5400 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

Docket No. 50-206 Response to Generic Letter 88-14, "Instrument Air Supply System Problems Affecting Safety-Related Equipment" San Onofre Nuclear Generating Station, Unit 1 INTRODUCTION The purpose of this letter is to provide our response to Generic Letter 88-14. All verification activities required by the generic letter have been completed with the exception of the valve failsafe position testing and the resolution of five items which require further review.

Listed below are the specific generic letter requirements followed by a discussion of our verification activities for each requirement.

1.

VERIFICATION BY TEST THAT ACTUAL INSTRUMENT AIR QUALITY IS CONSISTENT WITH THE MANUFACTURER'S RECOMMENDATIONS FOR INDIVIDUAL COMPONENTS SERVED.

1.1 Verification Activities Complete Instrument air quality was assessed and concluded to be acceptable. This conclusion was based on the following:

  • Equipment performance,
  • History of operation and maintenance,
  • Dewpoint measurements, and
  • Blowdowns of the Instrument Air System.

1.2 Verification Activities Outstanding 1.2a In order to reconfirm our conclusion, we will perform laboratory tests of the air quality. To ensure that the air quality testing is performed during normal system operating loads and configuration, the air quality testing will be performed after startup from the Cycle 11 refueling outage. We will provide you with the results of the air quality tests within sj y nths after return to service from the Cycle 11 refueling outage.

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Document Control Desk August 30, 1990 1.2b Verification of desiccant in the Instrument Air System remains outstanding. The instrument air filter is located downstream of the desiccant dryer and prevents desiccant or other detrimental particulate from entering the Instrument Air System. There was a desiccant breakdown incident at SONGS-1 in March 1980. The desiccant contaminated the internals of various components. The problem was successfully resolved by replacing the affected components and by cleaning the instrument air lines. In addition, a new filtration system that prevents air from bypassing the filter media was installed.

In September 1989, desiccant was identified as contributing to the failure of a solenoid valve that had air supplied from the Instrument Air System. The root cause investigation, which included inspecting similar solenoid valves located throughout the plant with air supplied from the Instrument Air System, indicates the failure of the solenoid valve was an isolated occurrence caused by residual desiccant from the 1980 incident. A follow-up Cycle 12 refueling outage inspection will be performed to confirm this conclusion. We will inform you of the results of the inspection at the end of the Cycle 12 refueling outage.

1.2c As a result of the 1980 desiccant breakdown incident, we instituted an Instrument Air System blowdown and inspection program. The supply lines and inlet filters to various components were inspected for evidence of desiccant and moisture. In response to the generic letter, we will review our inspection program and provide the results of our review to you by November 30, 1990.

2.

VERIFICATION THAT MAINTENANCE PRACTICES, EMERGENCY PROCEDURES, AND TRAINING ARE ADEQUATE TO ENSURE THAT SAFETY-RELATED EQUIPMENT WILL FUNCTION AS INTENDED ON LOSS OF INSTRUMENT AIR.

2.1 Verification Activities Complete The maintenance practices, operating procedures, and training program were reviewed for adequacy. As a result of this review, the operating procedures were revised to clarify the instructions for coping with design basis accidents. No changes were required for the maintenance practices or the training program. All verification activities are complete.

3.

VERIFICATION THAT THE DESIGN OF THE ENTIRE INSTRUMENT AIR SYSTEM INCLUDING AIR OR OTHER PNEUMATIC ACCUMULATORS IS IN ACCORDANCE WITH ITS INTENDED FUNCTION, INCLUDING VERIFICATION BY TEST THAT AIR-OPERATED SAFETY-RELATED COMPONENTS WILL PERFORM AS EXPECTED IN ACCORDANCE WITH ALL DESIGN-BASIS EVENTS, INCLUDING A LOSS OF THE NORMAL INSTRUMENT AIR SYSTEM. THIS DESIGN VERIFICATION SHOULD INCLUDE AN ANALYSIS OF CURRENT AIR-OPERATED COMPONENT FAILURE POSITIONS TO VERIFY THAT THEY ARE CORRECT FOR ASSURING REQUIRED SAFETY FUNCTIONS.

Document Control Desk August 30, 1990 3.1 Verification Activities Complete The verification of design of the entire Instrument Air System was performed at San Onofre Unit 1 as requested by the generic letter. The results indicate that the San Onofre Unit 1 Instrument Air System design is adequate to ensure that air operated safety-related components perform their intended safety function.

The analysis of the design basis valve failure positions for all safety-related air-operated valves has been completed. As a result of the design basis review effort, we identified deficiencies in the Component Cooling Water System, Containment Spray System, and the Hot Leg Recirculation System. The corrective actions for these deficiencies were addressed in LER 89-003, "Nonconservative Failure Mode of Component Cooling Water Valves Due To Inadequate Single Failure Analysis," LER 89-024, "CV-517 and CV-518 Failure Mode on Loss of Instrument Air," and LER 89-025, "CV-305 and FCV-1112 Single Failure Deficiency with Hot Leg Recirculation."

3.2 Verification Activities Outstanding 3.2a The testing of the loss of normal instrument air valve failure position is nearly complete. As a result of the testing, we identified a deficiency in a Chemical and Volume Control System valve. The corrective action for this deficiency was addressed in LER 90-006, "Nonconservative Failure Mode of Chemical and Volume Control Valve CV 406B."

The testing is scheduled for completion by November 1990. We will provide you with the final test results by November 30, 1990.

3.2b Verification of the functional testing for valves which are served by the Instrument Air System and have a Safety-Related Nitrogen Backup System remains outstanding. Functional testing of these valves was performed following installation of the Nitrogen Backup System. We intend to take credit for the post-installation testing to meet the design verification requirements of the generic letter. A review of the post-installation test records will be conducted to verify that all testing meets current post-installation standards. We will provide you with the results of the review by November 30, 1990.

3.2c Verification of the Instrument Air System flowrate remains outstanding.

The FSAR design flowrate of the system is 100 SCFM. During the verification program, it was estimated that the air system flowrate is at least 300 SCFM. This estimate was based on the cycling of the air compressors. A flow meter will be installed during the Cycle 11 refueling outage. Instrument Air System flow data will be collected during the first three months of Cycle 11.

Based on this data an appropriate system flowrate will be determined and the FSAR will be updated as appropriate. We will provide you with the results within six months after return to service from the Cycle 11 refueling outage.

Document Control Desk August 30, 1990

4.

IN ADDITION TO THE ABOVE, PROVIDE A DISCUSSION OF THE PROGRAM FOR MAINTAINING PROPER INSTRUMENT AIR QUALITY.

As requested in the generic letter, a discussion of our program for maintaining proper instrument air quality is provided below.

The Instrument Air System is subjected to a periodic inspection and maintenance program. Once per shift, an operational surveillance verifies the correct cycling of the Instrument Air System Dryer desiccant towers, monitors the dew point, and verifies that the regenerative temperature is within the correct range. The differential pressure across the Instrument Air System filter is checked at least once per shift. Blowdowns of major components such as the air receivers, the aftercooler drain connections, and the unloader filter and wye strainer, are performed at least once per shift.

In addition, maintenance orders are used to ensure that the filters are inspected and replaced, as necessary, every three months and that the desiccant is sampled and examined every six months, and replaced at least every three years. The compressors are inspected and the oil sampled and changed quarterly. The compressor inlet and discharge valves are inspected annually. The compressor motors are overhauled every five years. Also included in the maintenance program are miscellaneous components such as gages, relays, switches, and pressure transmitters.

Document Control Desk August 30, 1990

5.

CONCLUSION We intend to provide the results from the loss of normal instrument air testing (3.2a), the review of the blowdown inspection program (1.2c), and the review of valve post-installation testing (3.2b) by November 30, 1990. The results from the air quality laboratory tests (1.2a) and the Instrument Air System flowrate measurements (3.2c) will be provided to you within six months of return to service from the Cycle 11 refueling outage. Finally, the resolution of the verification of an isolated incident of residual desiccant (1.2b) will be provided to you by the end of the Cycle 12 refueling outage.

If you have any questions regarding this matter, please let me know.

Respectfully submitted, By F.7R.

an dy_

Manager, Nuclear Licen g

Subscribgd and sworn to before mel this day of L2 Notary Public) in-the State of California cc:

J. B. Martin, Regional Administrator, NRC Region V C. W. Caldwell, NRC Senior Resident Inspector, San Onofre