ML18139A129
| ML18139A129 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 03/07/1980 |
| From: | Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-79-27, NUDOCS 8004080270 | |
| Download: ML18139A129 (4) | |
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VIRGINIA ELEcTR1c AND PowER OoMPA'.NY*-_.,,: - :,..
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"RICHHOND,VIB.GIN.lA 23261 March 7, 1980 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II Serial No. 185 PO/RGS:smv 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
IE BULLETIN 79-27 NORTH ANNA POWER STATION UNITS 1 AND 2 SURRY POWER STATION UNITS 1 AND 2 This is in response to IE Bulletin 79-27; Loss of Non-Class IE Instrumentation and Control Power System Bus During Operation".
We have not completed our review of the subject bulletin, but the following interim response to IE Bulletin 79-27 provides the status of our review to date.
NRC Request "Cl) Review the class IE and non-class IE buses supplying power to safety and non-safety-related instrumentation and control sys-tems which could affect the ability to achieve a cold shutdown..,/"'\\
condition using existing procedures or procedures develop.,ed'
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r under item 2 below.
For each bus:
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a)
Identify and review the alarm and/or indication provided.
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in the control room to alert the operator to the loss of power to the bus.
b)
Identify the instrument and control system loads connected to the bus and evaluate the effects of loss of power to these loads including the ability to achieve a cold shut-down condition.
c)
Describe any proposed design modifications resulting from these reviews and evaluations, and your proposed schedule for implementing those modifications."
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VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. James P. O'Reilly, Director Response NRC Request l.a The results of our review indicates that the operator has available in the control room alarm and/or direct indica-tion for the loss of power to the vital and D.C. distribu-tion systems for the North Anna and Surry stations. There are no alarms and/or direct indications for the loss of semi-vital buses in the control room.
However, the opera-tor can be alerted by a combination of alarms and/or indication from individual instruments or equipment and determine that a loss of power has occurred.
- 1. b All. instrument and control system loads connected to the vital, semi-vital and D.C. buses have been identified for North Anna Units 1 & 2 and Surry Unit 1.
The reyiew of each bus for Surry Unit 2 will be completed in the near future.
It is anticipated that the evaluation of the effects of loss of power to these loads including the ability to achieve hot and cold shutdown conditions will be completed by June 1, 1Q80.
1.c If any design modifications resulting from our review and evaluation are required, we will provide a schedule for the implementation of those modifications.
"(2)
Prepare emergehcy procedures or review existing ones that will be used by control. room operators, including procedures required to achieve a cold shutdown condition, upon loss of power to each class IE and non-class IE bus supplying power to safety and non-safety-related instrument and control systems.
The emergency procedures should include:
a)
The diagnostics/ alarms/ indicators/ symptoms resulting from the review and evaluation conducted per item 1 above.
b)
The use of alternate indication and/or control circuits which may be powered from other non-class IE or class IE instrumentation and control buses.
c)
Methods for restoring power to the bus.
Describe any proposed design modification of administrative con-trols to be implemented resulting from these procedures, and your proposed schedule for implementing the changes."
Response
- 2.
In an effort to provide the comprehensive review and evalu-ation of the emergency procedures that has been requested, it is our intent to complete the review and evaluation of
e VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. James P. O'Reilly, Director NRC Request item 1 prior to addressing all the concerns set forth in item 2.
We are continuing our review of existing proce-dures, but based on the above approach, we intend to respond with the results of our review and actions to be taken on or before June 1, 1980.
"(3)
Re-review IE Circular No. 79-02, Failure of 120 Volt Vital AC Power Supplies, dated January 11, 1979, to include both class IE and non-class IE safety-related power supply inverters.
Based on a review of operating experience and your re-review of IE Circular No. 79-02, describe any proposed design modifica-tions or administrative controls to be implemented as a,, result of the re-review."
Response
- 3.
We have rereviewed IE Cir~ular 79-02 to include non-class IE power supply invert~rs.
The following describes the results of our review for both class IE and non-class IE inverters.
a)
For North Anna Units 1 and 2 class IE inverters, there is no time delay circuitry or direct alternate 120VAC current input.
The alternate DC power supply is from batteries. There is an alternate 120VAC power source whicli is manually actuated through an external trans-fer switch.
This is used only as a maintenance by-pass device.
Based on this arrangement, items 1, 2 and 3 to the referenced Circular are not applicable.
With regard to item 4, maintenance procedures include reset of the manual transfer switch after maintenance is complete and ensures operability of the safety system.
For North Anna Units 1 and 2 non-class IE inverters, there are two inverters which supply power to each of the two units computers.
Unlike vital bus inverters, each computer inverter has a static transfer switch which switches automatically to an alternate AC source upon loss of inverter output.
This transfer also may be done manually.
There is no time delay between loss of inverter output and automatic transfer, therefore, item 1 of the Circular does not apply.
There is no AC input to the computer inverter, therefore, item 2 does not apply.
The station operating history indi-cates the maximum availability of the computer inverter to continuously supply the load and requires no modi-fication of the transfer circuitry or setpoints per item 3.
Administrative controls, item 4, exist to ensure operability of safety systems after subcom-ponents have been subjected to maintenance or testing.
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- e VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. James P. O'Reilly, Director RGS/smv:5F6 b)
The rereview of IE Circular 79-02 for Surry Units 1 and 2 has not been completed.
We expect to have this review complete by April 15, 1980.
c)
In general, the administrative controls employed at North Anna and Surry ensures the operability of safety systems after maintenance by the performance of asso-ciated periodic tests, which directly check the in-strumentation and control logic without the initiation of the safety function.
Very truly yours,
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'~- "l C. M. Stallings Vice President - Power Supply and Production Operations cc: Mr. Victor Stello, Director Office of Inspection and*.Enforcement