/%

U ATTACHMENT

& EGnG ,, L'

FOAM EO4G 3ee'"

INTERIM REPORT.

Accession No.

Report No. EGG-EA-5048RE-A-79-138

Contract Program or Project Title:

Electrical, Instrumentation and Control System Support

Subject of this Document:Electrical, Instrumentation and Control Aspects of the Override of ContainmentPurge Valve Isolation and other Safety Feature Signals, Salem Generating Station,Unit Nos. 1 and 2, Docket Nos. 50-272 and 50-311, TAC 08993

Type of Document:

Informal Report

Author (s):

A. C. Udy

Date of Document:

November 1979<

Responsible NRC Individual and NRC Office or Division:

Paul Shemanski, Division of Operating Reactors

This document was prepared primarily for preliminary or internal use. it has not receivedfull review and arc-' val. Since there may be substant|ve changes this document shouldnot be considerea smal.

EG&G Idaho, Inc.Idaho Falls, Idaho 83401

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Prepared for theU.S. Nuclear Regulatory Commissionand the U.S. Department of Energy.

Idaho Operations Office

! NRC FIN No..

|A6256

INTERIM REPORT

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TECHNICAL EVALUATION REPORT

ELECTRICAL, INSTRUMENTATION, AND CONTROL ASPECTS OFTHE OVERRIDE OF CONTAINMENT PURGE VALVE ISOLATION

AND 0"'HER SAFETY FEATURE CIGNALS

SALEM GENERATING STATION, UNIT NOS. 1 AND 2

Docket Nos. 50-272 and 50-311,

TAC 08993:

s November 1979

A. C. UdyEG6G Idaho, Inc.

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CONTENTS

1.0 INTRODUCTION . . . . . . . . ..............,.,, 1.

2.0 EVALUATION OF SALEM GENERATING STATION UNITS 1 AND 2 . . . . . . 2,

2.1 Review Criteria . 2. . . .......... ........2.2 Containment Ventilation Isolation Circuits Design

Description . . . . . . . . . . . . . . . . . . . . . . . . 32.3 Containment Ventilation Isolation System Design

Evaluation 4. . . . . . ............... ...

2.4 Other Engineered Safety Feature System Circuits . 6.....

3.0 CONCLUSIONS 6. . . . . . . . .............. ....

4.0 REFERENCES . . . . . . . . . . . . . . . . . . . . . , , 7,,,,

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TECHNICAL EVALUATION REPORT

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ELECTRICAL, INSTRUMENTATION, AND CONTROL ASPECTS OFTHE OVERRRIDE OF CONTAINMENT PURGE VALVE ISOLATION

AND OTHER SAFETY FEATURE SIGNALS

SALEM GENERATING STATION, UNIT NOS. 1 AND 2

1.0 INTRODUCTION

Based on the information supplied by Public Service Electric andGas Corporation (PSE&G), this report addresses the electrical, instru-mentation, and control systems design aspects of the Containment Venti-,

lation Isolation (CVI) system and other Engineered Safety Feature (ESF)system functions for the Salem 1 and Salem 2 plants. PSE&G has verified

1that these systems are identical in both plants .

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Several instances have been reported where the automatic closureof the containment ventilstion or purge isolation valves would not have,

occurred because the safety actuation signals were manually overriddenI

or blocked during normal plant operations. These events resulted froma lack of proper management controls, procedural inadequacies, andcircuit design deficiencies. PSE&G was one of the licensees who first '

reported a reportable occurrence of this type . It was found that,when the CVI system is reset without removing the isolation actuationsignal, additional Safety Injection (SI) signals are prevented from

| initiating containment isolation. Administrative controls were imposedi until a design change could be incorporated.|

These events also brought into question the mechanical operabilityof the valves themselves. These events were determined by the Nuclear

. Regulatory Commission (NRC) to be an Abnormal Occurrence (#78-05) and

accordingly, were reported to Congress.*

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| As a follow-up of this Abnormal Occurrence, the NRC is reviewing*

the electrical override aspects and the mechanical operability aspectsof containment purging for all operating reactors. On November 28,1978, the NRC issued a letter, " Containment Purging During Normal Plant

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Operation" to all Boiling Water Reactor (BWR) and Pressurized Water4Reactor (PWR) licensees. PSE&G responded to the letter saying

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that, " Manual override circuitry has been changed to prevent the by-passing of the safety signal." Howevar, Reference 5 reported anotherreportable occurrence where a radiation channel alarmed but did not

initiate containment isolation. This was attributed to failure toreset another radiation channel alarm prior to resetting the CVI system.

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PSE&G states in Reference 6 that "Our design is no longer subjectto override conditions which could prevent automatic valve closureduring a LOCA."

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2.0 EVALUATION OF SALEM CENERATING STATION UNITS 1 AND 2

2.1 Revicw Criteriona

The primary intent of this evaluation is to determine if the fol-.

loving requirements are met for the safety si nals to all purge andF

ventilation isolation valves:

(1) Criterion No. 1--The overriding of one type ofs-

safety actuation signal (e.g., radiation) must notcause the blocking of any other type of safetyactuation signal (e.g., pressure) to the isolationvalves.-

(2) Criterion No. 2--Sufficient physical features (e.g.,| key lock switches) are provided to facilitate ade-I quate administrative controls.

(3) Criterion No. 3--A system level annunciation of theoverridden status is provided for every safetysystem impacted when any override is active.

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Incidental to this review, the following additional NRC designcriteria were used in the evaluation:

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(a) The following definition is given for clarity of use in this"

evaluation:

Override: The signal is still present, and it is blocked in orderto perform a function contrary to the signal.

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(1) Criterion No. 4--Diverse signals should be provided |to initiate isolation of the containment ventila-i

tion system. Specifically, containment high radi-.

ation, safety injection actuation, and containmenthigh pressure should automatically initiate CVI.

(2) Criterion No. 5--The instrumentation and control| systems provided to initiate CVI should be designed

and qualified as safety grade equipment.

(3) Criterion No. 6--The overriding or resettinga ogthe isolation actuation signal should not cause theautomatic reopening of any isolation or purge valve.

2.2 Containment Ventilation Isolation Circuits Design Description

Each of the Salem units has two ESF trains which close indepen-dently and separately the inboard and outboard isolation valves. Thevalves are opened by manual control only. The initiating signals which

j override any opening signal are listed below:o

' Manual

1. Pressing either of two momentary pushbuttoa switcheswill actuate both trains of contaiment isolationphase A (all non-essential process lines) and CVI.

2. Simultaneous pressing a single pair (of two pairs)of momentary pushbutton switches will actuate bothtrains of containment spray and CVI.

Either of the above two signals, once initiated,will continue until manually reset by a separatemomentary pushbutton switch. (A single switch pertrain resets either signal.)

Automatic1

1. Any of the following containment radioactivitylevels exceeds its setpoint:

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(a) The following definition is given for clarity of use in thisevaluation:.

| Reset: The signal has come and gone, and circuit is being cleared'

in order to return it to the normal condition.

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a. Air particle monitor

b. Iodine monitor

c. Radioactive gas moc' tor

2. SI signal, which may be initiated by any of thefollowing

a. Pressuriser level and pressure low

b. Containment pressure high

c. Steam line differential preseure high

d. Steam line flow high coincident with eitherT low or steam line pressure low.ay,

The actuation signal resulting from the automaticinitiation signal can be reset from the ESF panelto allow manual opening of the CVI valves.

Manual control of the valves is by momentary contact pushbutton,

( switches. The control system is such that the automatic closure sig-nals will close the valves even if the "open" pushbutton is depressed.e

The control system also prevants valve opening except when the "open".

pushbutton is erercised, thus preventing reopening of the valves whenthe "close" signal is removed. Loss of power to the control system or

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loss of air to the solenoid valve closes the isolation valves. Valveposition lights, open and closed, are provided on the control console.

2.3 Containment Ventilation Isolation System Design Evaluation

Each train of CVI in the solid state ESF has a retentive memorywith " manual reset." Briefly, sM uld an actuation signal be present,

I and then a " manual reset" perfor d, the " manual reset" signal remainspresent as long as the actuation signal is present, thus functioning as

- a signal override, as defined in Section 2.0 of this report.

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Each CVI train is automatically actuated by either a high radiationsignal or a safety injection signal through an "0R" gate. If either

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| signal actuates the CVI and then is overridden, the other signal then|

| could not possibly actuate the CVI until after all actuation signals1

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are gone. The fact that an actuation signal is overridden is not

annunciated. Both the signal blocking and the non-annunciation is not |

in conformance with NRC criteria.

After the first reportable occurrence , a spare SI actuation:

relay contact was placed in series with the solenoid valve control l

power for Salen Unit 2, in addition to the connection through the "OR" )gate. This was also recently completed for Salem Unit 1 . Thispermits any SI actuation signal to additionally actuate the CVI regard-less of the condition of the radiation signal and override. Blockingof the SI signal to deenergize safety injection and to allow opening ofthe CVI valves will not prevent the radiation channels from initiating |

isolation nor will this action open the CVI valves as these can be !1

opened only by pushbutton switch. These features are now in conform- |

ance with NRC criteria.b

bovever,usingthemanualresettooverrideoneradiationsignal'

overrides the other five signals also. Since the same type signal isinvolved, this is in conformance with the NRC criteria. Each radiationsignal is annunciated separately, as is the operational bypass. Thiswill alert the operator of potential problems.

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l Additionally, should the SI signal be overridden at the CVI reten-tive memory instead of the normal "SI blocked function," the radiationsignals would be bypassed. Administrative controls are required here.

The four signals for SI actuation (as listed in Section 3) agreeI with the NRC position that inputs to safety actuation circuits should

be diverse.

Additionally, the CVI circuit monitors the status of two channelsor a.ontainment radiation level adding further diversity to CVI actua-,

1tion . Each radiation channel monitors (a) particulate level, (b)iodine level, and (c) radioactive gas level. One channel monitors the.

containment, while the other channel monitors the plant stack, both via

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sample lines which are blocked in the event of high pressure (the pres-surs signals are independent of those for the SI actuation). Shouldany one of the six radiation levels (two locations, three variablesjach) be high, CVI is initiated on both trains. These radiation moni-tors are not located inside of containment, and are not relied on tomonitor containment radiation in a post-accident condition (since thesample lines are isolated from containment on a high pressure signal).Isolation status lights for the radiation monitoring system are adja-cent to the radiation readouts to indicate if the monitor sample streamsare functional. The monitors are seismically qualified and testable,and are powered by vital AC power buses.

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The criteria that sufficient physical features be present to pro- |

vide for adequate administrative controls is not met as the pushbutton !switches for actuating resets, overrides, and valve opening are not

' protected from accidental actuation.

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2.4 Other Engineered Safety Feature System Circuits

The CVI is the only portion of the ESF where two signals were"0R"ed together to a common retentive memory with manual reset. This .

reset affects no other portion of the ESF system. Other ESF circuitsare not prone to the same failure mechanism.

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3.0 CONCLUSIONS

The electrical, instrumentation, and control design aspects of thecontainment ventilation isolation valves and other ESF signals for theSalem plants were evaluated using tne design criteria stated in Sec-tion 2.0 of this report. We determined that (a) the ESF system is.not

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now prone to overriding actuation signals should another signal beoverridden to establish manual control (per criteria 1), (b) suffici-,

. ently diverse actuation signals are present to actuate CVI, and (c) theoverriding of or the release from an isolation actuation signal willnot cause automatic reopening of the isolation valves.

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Provided that (a) spring loaded transparent covers are installedon the pushbutton control and override switches, (b) provisions forsystem level annunciation of overridden actuation signals are made, and(c) the radiation channels be qualified as safety grade equipment, theSalem 1 and Salen 2 plants would be in full compliance with the NRCcriteria and guidelines. These items have been discussed with thelicensee . PSE&G has not voluntarily agreed to these changes; how-ever, the licensee has expressed willingness to make the changes ifthey are required by the NRC.

We recommend that PSE&G be required to submit plans to bringSalem Unit Nos. I and 2 into conformance with Criterions 2, 3, and 5 asstated in Section 2.0 of this report.

4.0 REFERENCES,

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l1. Telecon, J. T. Beard, NRC-DOR, J. Gagliardi, PSE&G, A. C. Udy,'

EG&G Idaho, September 9, 1979.

2. PSE&G 1etter, F. P. Labrizzi, to B. H. Utier, NRC licenseNo. DPR-70, Docket No. 50-272, Reportable Occurance 78-61/01T,September 19, 1978.

3. NRC/ DOR letter (A. Schwencer) to all BWR and PWR licensees," Containment Purging During Normal Plant Operation," datedNovember 28, 1978.

4. PSE&G 1etter, F. P. Librizzi to A. Schwencer, NRC, " ContainmentPurging During Normal Plant Operation," Salem Generating Station,Unit No. 1, Docket No. 50-171, December 21, 1978.

5. PSE&G letter, F. P. Librizzi to B. H. Grier, NRC, License I

N3. DPR-70, Docket No. 50-272, Reportable Occurrence 79-11/01T,January 30, 1979.

6. PSE&G 1etter, F. P. Librizzi to A. Schwencer, NRC, " ContainmentPurging During Normal Plant Operating, Salem Generating Station,.

Unit No. 1, Docket No. 50-272, Jrnuary 30, 1979.*

7. Telecon, J. T. Beard, NRC-DOR to J. Gagliardi, PSE&G, September 13,1979.

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