ML20149L387
| ML20149L387 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 02/19/1988 |
| From: | Cockfield D PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-64533, NUDOCS 8802240210 | |
| Download: ML20149L387 (4) | |
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g HE blNV David W. Cockfield Vice President, Nuclear February 19, 1988 Trojan Nuclear Plant Docket. 50-344 License NPF-1 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555
Dear Sir:
Response to Request for Additional Information License Change Application 150 By your letter dated January 12, 1988, Portland General Electric Company received a request for additional information on License Change Application 150.
This proposed license change would revise Trojan Technical Specification surveillance requirements for safety injection accumulator isolation valves. Attached is our response to your request.
Sincerely, VJ b
Attachment c:
Mr. John B. M/;rtin Regional Administrator, Region V U.S. Nuclear Regulatory Commission Mr. R. C. Bare j
Residerit Inspector Trojan Nuclear Plant Mr. William Dixon State of Oregon Departstrent of Energy Mr. Michael J. Sykes Chairman of County Commissioners 8002240210 880219 PDR ADOCN 05000344
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a Trojan Nuclear Plant Document Control Desk Docket 50-344 February 19, 1988 License NPF-1 Attachment Page 1 of 3 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION LICENSE CHANGE APPLICATION 150 Information Request 1 Verify that correct operation of the lockout switch contact will be tested at least once every 12 months during the shutdown. The Trojan Technical Specification should be revised to include this action.
Response
Correct operation of the lockout switch contact will be verified every year during the annual refueling outage.
For that reason, the surveil-lance frequency of "R",
at least once per 18 months is the proposed periodicity. This periedicity is consistent with other survelliance requirements performed during the annual refueling outage period. License Change Application 150 is being revised to include this commitment.
Information Request 2 Provide a discussion of the independence of the slider contacts which provide the lockout function on the accumulator isolation valve control i
switch to the rotating contacts which provide the operating function.
Describe any single electrical or mechanical failure that could simul-taneously cause the lockout contacts and operating contacts (in the valve close circuit) to close or remain closed when the switch is placed in the lockout position.
Response
The configuration of the proposed switch incorporates two physically separate switch actions into a single switch. Rotary contacts provide j
normal control of valve motion, while lateral (slider) contacts provide lockout of the entire valve control circuit. The two types of contacts are located in different contact stages and are electrically and mechanically isolated from one another via a glass / polyester barrier.
A common actuating shaf t causes the various contacts to change state according to the predetermined switch contact configuration. Rotary contact actuators (cams) are designed and fitted to the shaft in such a manner that they may only change states when the handle is rotated clock-wjJe or counterclockwise.
Similarly, the lateral (slider) contact cams are designed and fitted to the shaft in such a manner that they may only change states when the handle is pulled out or pushed in.
Two mechanical detent mechanisms on the rear of the switch prevents rotary action while the switch is pulled out and conversely prevents lateral action when the switch is rotated while pushed in.
Trojan Nuclear Plant Document Control Desk Docke: 50-344 rebriv y 19, 1988 License NPF-1 Attachment Page 2 of 3 Mechanical f ailure of the switch cams can result in misoperation of either the rotary or the lateral contacts; however, simultaneous failures of both types of switch actuators (cams and detents) constitute two independent failures. Therefore, no single mechanical failure, with the exception of gross mechanical deformation, can cause both valve circuit lockout con-tacts and operating contacts to close or remain closed when circuit lock-out is initiated. Gross mechanical failure is not considered a credible event for this installation.
No single electrical failure can simultaneously cause the lockout contacts and operating contacts to close or remain closed when th2 swite.h is in the lockout position.
Simultaneous electrical failure of both types of con-tacts could only occur with the switch in the non-lockout position.
If an uncleared fault were to exist on the control circuit as a result of failure of two Class IE devices (control circuit fuse and 480 V motor feeder circuit breaker) and the switch was rotated counterclockwise to the "close" position, then high current flow due to the fault could weld the close initiation contact and the two lockout contacts shut. However, this scenario involves multiple, independent failures and would require manual initiation of valve motion while in the non-lockout position.
The design of the proposed lockout switch is considered adequate to prevent spurious misoperation of the accumulator isolation valves. No single credible failure can cause an undetectable sequence of events which could result in undesired isolation of an aceveulator.
Furthermore, the manufacturer's operating experience and failure history with similar switches does not indicate any common-mode failure mechanism which could cause simultaneous failure of both lateral and rotary contacts. Manu-facturer's failure history does not indicate significant potential for any ringle mechanical failure as described above.
Infot. ition Request 3 Reference an operating procedure which controls the removal of the block-ing collar f rom the accumulator isolation control switch when it is in the lockout position.
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Response
Administrative Order (AO) 3-13. "Control of Locked Valves and ESF (Engineered Safety Features] Equipment", outlines the procedure for the control of this type of switch. This order specifically requires the permission of the Shif t Supervisor or Assistant Shif t Supervisor prior to changing the position of any administratively controlled switch when the reactor is in Modes 1, 2, 3, and 4.
This order would be apprupriate to specifically control the accumulator isolation valve control switches upon installation of the pull-to-lockout feature.
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Trojan Nuclear Plant Document Control Desk Docket 50-344 February 19, 1988 License NPF-1 Attachment Page 3 of 3 Information Request 4 Provide a discussion of the alarms available in the control room that alert the operator to an accumulator isolation valve that is not in the fully open position. Are the power supplies and limit switches to these alarms independent of those which provide valve position indication at the accumulator isolation valve control switch?
Response
Each of the four accumulator isolation valves, MO 8808A, B, C, and D, have individual annunciator windows in the control room.
An alarm will i
occur when a valve is not fully open and the system is under pressure.
This condition is independently sensed by a cam switch in the motor operator and an externally mounted stem-operated switch.
These switches are connected in parallel to provide redundant alarm initiation. Valve position indication is provided by separate cam switches in the motor l
operator. The power sources for the alarm circuits and valve position indication circuits are separately derived for additional independence.
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DLN/kal 6037k.288