ML19323G524

Responds to IE Bulletin 79-27, Loss of Non-Class IE Instrumentation & Control Power Sys Bus During Operation. Review Identified Need to Increase Reliability of Ac Power Supplied to non-nuclear Instrumentation Sys

ML19323G524
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/23/1980
From:	Trimble D ARKANSAS POWER & LIGHT CO.
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
IEB-79-27, NUDOCS 8006040051
Download: ML19323G524 (5)

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j NSIC ARKANSAS POWER & LIGHT COMPANY POST OFRCE BOX 551 UTTLE ROCK. ARKANSAS 72203 (5011371-4000. -

April 23, 1980 1-040-15 Mr. K. V. Seyfrit, Director Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011

Subject:

Arkansas Nuclear One-Unit 1 Docket No. 50-313 License No. DPR 51 IE Bulletin 79-27 (File:

1510.1)

Gentlemen:

In accordance with our letter of April 1,1980, the following is our response to the subject bulletin for ANO-1.

By letter dated Feb-ruary 28, 1980, a response for ANO-2 was provided.

Item 1:

l Review the class 1-E and non-class 1-E buses supplying power to safety and non-safety related instrumentation and control systems which could affect the ability to achieve a cold shutdown condition using existing procedures or procedures developed under item 2 below. For each bus:

f a) identify and review the alarm and/or indication provided 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 in-cluding the ability to achieve a cold shutdown condition.

c) describe'any proposed design modifications resulting from these reviews and evaluations, and your proposed schedule for implement-ing those modifications.

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Response

Our review of the class 1-E and non-class 1-E buses supplying power to safety and non-safety related instrumentation and control systems which could affect the ability to achieve a cold shutdown condition identified the need to increase the reliability of A.C. power supplied to the Non-Nuclear Instrumentation System. Attachment 1 is a listing of the parameters which we feel are necessary to achieve a safe shutdown con-dition. The attachment gives the effect of various power loss events on each of the parameters. We feel that the addition of a transfer switch which will provide an alternate, diesel generator-backed source of A.C.

power to the NNI system upon loss of vital 120 V.A.C. inverter power will significantly enhance the reliability of the NNI system.

This modifi-cation will prevent the loss of A.C. power to the NNI system due to any single failure of a 120 V.A.C. power supply.

This modification will be completed prior to power operation after June 21, 1980.

In response to the Item 1.(a), the ANO-1 design provides for annunciation of vital bus status.

Also, the status of the back-up power source which will be prdvided via the automatic transfer switch is annunciated.

Item 2:

Prepare emergency 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 1-E and non-class 1-E bus supplying power to safety and non-safety related instru-meat and control systems. The emergency procedures should include:

a)

The diagnostics / alarms / indicators / symptom 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 1-E or class 1-E instrumentation and control buses.

c)

Methods for restoring power to the bus.

Describe any proposed design modification or administrative controls to be implemented resulting from these procedures, and your proposed sched-ule for implementing the changes.

Response

As a result of our review of the NNI/ICS system, emergency procedures have been amplified to provide additional guidance to operators during transients.

This additional guidance includes (1) which instruments to monitor in the event of various power supply failures and (2) corrective action that can be taken. The procedure revisions are complete. Any procedural modifications we deem necessary as a result of the modifica-tion described in response to Item 1 alone will be completed prior to power operation after June 21, 1980.

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I Item 3:

Re-review IE Circular No. 79-02, Failure of 120 Volt Vital AC Power Supplies, dated January 11, 1979, to include both class 1-E and non-class 1-E safety related power supply inverters.

Based on a review of operating experience and your re-review of IE Circular No. 79-02, de-scribe any proposed design modifications or administrative controls to be implemented as a result of the re-review.

Response

As the incident described in IE Circular No. 79-02 occurred at the Arkansas Nuclear One site, review of the incident has been completed.

IE Inspection Report No. 50-313/79-02 identified the ANO-1 invertors as an area of concern, and stated the inverters (i.e., class 1-E and non-class 1-E) should be checked in a manner similar to that for the ANO-2 inverters.

Subsequent to our review, no design modifications or ad-ministrative controls were necessary or implemented as a result of our review.

Very truly yours, 0Y$f David C. Trimble Manager, Licensing DCT: MAS:nak

ATTACHMENT 1 Power Loss Power Loss Power Loss Power Loss Parameter 24VDC-X 24VDC-Y 118VAC-X 118VAC-Y Pressurizer Level C

C C

C Pressurizer Level Temp Comp SRX SRX i

Pressurizer Water g

g 3

Temp SIY C,SIX SCY C,SIX RC Outlet Temp (T )

h Loop A WR C

C C

C RC Outlet Temp (T }

h Loop B WR C

C C

C RC Inlet Temp (T )

c g

1 g

Loop A WR SIY C,SIX SCY C,SIX RC Inlet Temp (T )

g 1

Loop B WR SIY C,SIX SCY C,SIX I

OTSG A Startup Level C,SIX '

SCY C,SIX 3

I OTSG B Startup Level SCY SIX SCY SIX OTSG A Operating Level SRY C,SRX SCY C,SRX 2

OTSG B Operating Level C,SRY SRX SCY SRX OTSG A Pressure SIY C,SIX SCY C,SIX 1

OTSG B Pressure C,SIY SIX SCY SIX DH Removal Flow A I

I DH Removal Flow B I

I Makeup Tank Level C,SRX SCY C SRX BWST Level I

I I

RCS Wide Range Press.

R R

R l

DH Cooler Temp

{

Lop A DSCHG I,C I,C DH Cooler Temp l

Loop B DSCHG I,C I,C Saturation Meters Ch 2 R Ch 1 R Ch 2 R Ch 1 R

ATTACHMENT 1 (Continued)

Symbols:

(-) - Indicates none available C

- Computer J

I

- Indicator R

- Recorder Prefix S - Selectable between X or Y Suffix X or Y

- Denotes signal origin or dependency Notes:

1.

Either indication to operator and input to other function or computer input, but not both.

2.

Either recorded and input to other functions or computer input, but not both.

3.

Either X or Y transmitter can be selected for indication.

4.

Transmitter is from Engineered Safeguards.

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