ML20247K021

Responds to Generic Ltr 88-14, Instrument Air Supply Sys Problems Affecting Safety-Related Equipment, Clarifying Info in .Use of Unqualified Components in Vent Paths for Valves Acceptable Based on Secondary Side Cooling

ML20247K021
Person / Time
Site:	Oconee
Issue date:	07/21/1989
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-88-14, NUDOCS 8907310419
Download: ML20247K021 (6)

Text

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4 DmCE POWER GOMPANY P.O. DOX 33189 CHARLOTTE. N.O. 28242 IIAL B. TUCKER Teternown voor eme. amen (704) 373-4531-poos.can ruonsernow July 21, 1989 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Subject:

Oconee Nuclear. Station Docket hos. 50-265, -270, -287 Instrument Air Supply System Problems Affecting Safety Related Equipment Generic Letter 88-14 Gentlemen:

By letter dated May 8,1989 I submitted a response to Generic Letter 88-14 concerning Instrument Air (IA) System problems affecting safety related equipment. Attachment 1 to that letter provided the requested verifications and program discussion for the Oconee Nuclear Station. The purpose of this letter is to provide further clarification and correction of certain information provided in my letter of May 8, 1989 and to advise the NRC of the results of our continuing review of the IA System.

Item 3 of GL 88-14 requested a design verification of the entire IA System including verification by test that the air-operated safety-related  ;

components will perform in accordance with their intended function. Our response to this Item consisted of 5 parts. ]

Part 5, detailed in Attachment l'to my letter of May 8, 1989, concerned a verification that backup accumulators for certain valves are properly designed to perform 3 their intended function. Four valves in each Oconee unit'were identified I to have accumulators as a redundant source of air. These valves included 1, 2, 3 LPSW-516, -525 and 1, 2, 3 HP-5, -21. A design verification indicated that the accumulators were properly sized to perform their intended function. Furthermore, our response indicated that functional verification tests for these valves were scheduled to be performed by June 1, 1989. ,

Please be advised that the functional verification tests for these valves and accumulators were not performed as scheduled by June 1, 1989. Instead the overall approach for these valves described in my letter of May 8, '

1989 has been revised to include these valves and accumulators in the verification testing program. As such, these valves have been included in a list (Attachment A) of safety-related air-operated valves to be tested as required by GL 18-14. The list of safety-related air-operated valer, Attachment A, is intended to supersede in its entirety the list of 0conee air-operated active valves submitted as Supplement A to my letter of May 8, 1989.

0907310419 890721 PDR ADOCK 05000269 1 P PDC

Document Control Desk July 21, 1989 Page 2 The verification testing program will define the testing requirements to.

adequately simulate a loss of instrument air; review current testing proceduras for the identified valves to determine if current methods can .

adequately simulate a loss of instrument air, and if not, develop and schedule a test that does for that valve. The results of the verification.

testing program will be reported to the NRC when the program has been completed.

Part 4 of our response to Item 3 of the generic letter indicated that non-qualified components were discovered in the vent paths for-certain air-operated valves and that additional time is needed to fully assess the situation. A resolution to this item was expected by June 1, 1989. The following paragraphs provido a summary of our findings concerning this item.

The valves with non-qualified components (pneumatic positioners) in the vent paths include 1, 2, 3 HP-120; 1, 2, LPSW-251, -252'and 3 LPSW-404,

-405; and 1, 2, 3 F0W-315, -316. The pneumatic positioners used on control valves are subject to two types of failures. First, internal failure of bellows, diaphrams, or 0-rings would cause the positioner to take the valve fully open. Second, an external failure of the positioner linkage would result-in a loss of feedback and could cause the'7aive to go fully open or fully closed. This is a very unlikely mode of positioner-failure.

A review of the design basis for valves 1, 2, 3 HP-120 concluded that their operation is not required to prevent or mitigate the consequences of a design basis accident since no credit is taken for valve opening or closing. Therefore, none of the components in these valves are safety-related. These valves have.been removed from the list of air-operated valves requiring verification testing.

2 The positioner for valves 1, 2'LPSW-251, -252 and 3 LPSW-404, -405 is t'ne only component capable of closing these fail open valves given a loss of instrument air. A review of our maintenance data base did not indicate any positioner failures. More importantly, most of the failures noted were in the open position. In this case, backup EMO valves 1, 2, 3 LPSW-4, -5 are used to control for failure of the normal pneumatic valves.

Should either of the air-operated valves fail to operate, its. respective  ?

motor-operated valve can also be used. For the extramely rare case of a i failure in the closed position, reliability is casured via redundancy.

The system design calls for two independent trai.2, either of which can adequately perform its safety function. Therefore, the system as designed fulfills its design function for preventing or mitigating the consequences of a design basis accident.

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i Document Control Desk j July'21, 1989  !

Page 3 i Control-grade instrumentation is common in the Oconee Fr.argency Feedwater (EFW) System. 'The use of non-qualified instrumentation components for i valves 1, 2, 3.FDW-315, -316 is not considered to compromise plant safety .{

and is consistent with the design basis of the system. Taus, use of .

i non-qualified instrumentation from a design basis standpoint is considered acceptable.

Non qualified components themselves are not necessarily less reliable than i a system that is fully qualified. Even with the failure of a component, the redundancy of.EFW paths to the steam generators provides assurance-

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that the EFW function is not threatened. Additionally,-EFW is only one of'  !

many ways to provide secondary-side cooling to the steatr generators. j Other means include the use of: normal feedwater via the Main Feedwater ']

System, the Condensate System pumps, the Auxiliary Service Water System,  !

and the' Safe Shutdown Facility Auxiliary Service Water System. Safe plant i operation regarding secondary-side cooling is considered assured.

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i Thus, we conclude that use of non-qualified components in the vent paths i for these valves is acceptable and does not degrade capability to provide mitigation of design-basis events.

Very truly yours,

. b. .axf

(- y

. B. Tucker MAH/5/td

d Document Control Desk July 21, 1989 Page 4 cc: Mr. S. D. Ebneter Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta St., NW Suite 2900 Atlanta, GA 30323 Mr. P. H. Skinner NRC Resident Inspector Oconee Nuclear Station Mr. L. A. Wiens Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, DC 20555 I

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Document Control Desk July 21, 1989 Page 5 bec: R. L. Gill, Jr.

P. F. Guill P. J. North R. R. Eller N. A. Rutherford .

R. C. Futrell {

R. F. Cole i P. 3. Nardoci i G. W. Hallman j T. D. Curtis - ONS S. L. Nader S. Benesole - ONS ,

K. Chea -'ONS I D. P. Garland - ONS I D. Hubbard - ONS l L. A. Hentz j J. F. Norris i P. T. Farish i L. A. Reed J P. L. Stiles R. L. Sweigart - ONS T. N. Glenn - ONS J. D. Wylie T. S. Barr - ONS l E. M. Geddie Group File: 0S-815.07 i

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ATTACHMENT A..'

OCONEE AIR-0PERATED SAFETY-RELATED VALVES REQUIRING A LOSS OF AIR TEST (WITH OPERATOR FAILURE POSITIONS) l Vr.lve Tag Failure Position .]

-1, 2, 3 C-192- Closed 'i 1, 2,.3 CC-8 -C1 osed 1, 2, 3 CS-6 Closed-1, 2, 3'FDW-35 As Is*

1, 2, 3 FDW-44 As Is*

1, 2, 3 FDW-106 Closed 1,'2, 3 FDW-108 Closed 1, 2, 3 FDW-315 'Open 1, 2, 3 FDW-316 Open 1, 2, 3 HP.-5 Closed 1, 2, 3 HP-21 Closed 1, 2, 3 HPSW-184 Open 1, 2, 3 LPSW-138 Open 1, 2 LPSW-516 Open 1, 2 LPSW-525 Open 1, 2, 3 LWD-2 Closed 1, 2, 3 MS-87 .Open 1, 2, 3 MS-93 Open ,

1, 2, 3 PR-2 -Closed  :)

1, 2, 3 PR-5 Closed .]

1, 2, 3 PR-8 Closed '

1, 2, 3 PR-10 Closed 1, 2, 3 RC-7 Closed .)

• - Actuator is double-acting. On loss of air, valve will fail in the .

position it is in at that time.

System Key C - Condensate System CC - Component Cooling System CS - Coolant Storage System  ;

FDW - Main Feedwater System I HP High Pressure Injection System.(valves only) q HPSW - High Pressure Service Water System LPSW - Low Pressure Service Water System ,

LWD - Liquid Waste Disposal System MS - Main Steam System .

j PR - Penetration Room Ventilation System. j RC - Reactor Coolant System l

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