ML19305D181

Electrical,Instrumentation & Control Aspects of Override of Containment Purge Valve Isolation & Other Safety Feature Signals, Informal Rept

ML19305D181
Person / Time
Site:	Cook
Issue date:	02/29/1980
From:	Udy A EG&G, INC.
To:	Shemanski P Office of Nuclear Reactor Regulation
References
EGG-EA-5098, NUDOCS 8004140138
Download: ML19305D181 (13)

Text

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FOXM EG4G 398 INTERIM REPORT Accession No.

EGG-EA-5098 Report No.

Contract Program or Project

Title:

Electrical, Instrumentation and Control System Support Subject of this Document:

" Electrical, Instrumentation & Control Aspects of the Override of Containment Purge Valve Isolation & Other Safety Feature Signals, Donald C. Cook Nuclear Plant, Unit Nos. 1

& 2. Docket Nos. 50-315 and 50-316, TAC Nos. 10170/10169" Type of Document:

Informal Report Author (s):

A. C. Udy D:te of Document:

February 1980 R:sponsible 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 received full review and approval. Since there may be sut,3tantive changes, this document should not be considered final.

EG&G Idaho, Inc.

Idaho Falls, Idaho 83401

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H.1P.'Pearson, Supervisor Information Processing Prepared for the U.S. Nuclear Regulatory Commission and the U.S. Department of Energy Idaho Operations Office Under contract No. EY-76-C-07-1570 NRC FIN No.

A6256 INTERIM REPORT VRC lesearci anc ~echnical Assistance Report 8004140 38

EGG-EA-5098 February 1980 ELECTRICAL, INSTRUMENTATION AND CONTROL ASPECTS OF THE OVERRIDE OF CONTAINMENT PURGE VALVE ISOLATION AND o

OTHFR SAFETY FEATURE SIGNALS, DONALD C. COOK NUCLEAR f

i PLANT, UNIT NOS. 1 AND 2, DOCKET NOS. 50-315 AND l

50-316, TAC NOS. 10170/10169 A. C. Udy f

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FORM EO&G 3te (Rev.117%

INTERIM REPORT Accession No.

Report No.

EGC-EA-5098 Contract Program or Project

Title:

Electrical, Instrumentation and Control System Support Subject of this Document:

Electrical, Instrumentation and Control Aspects of the Override of Containment Purge Valve Isolation and Other Safety Feature Signals, Donald C. Cook Nuclear Plant, Unit Nos. 1 and 2, Docket Nos. 50-315 and 50-316, TAC Nos. 10170/10169 Type of Document:

Informal Report Author (s):

A. C. Udy D:t) of Document:

February 1980 R:sponsible 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 received full review and approval. Since there may be substantive changes, this document should not be considered final.

EG&G Idaho, Inc.

Idaho Falls, Idaho 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.

Under DOE Contract No. DE-AC07-76f D01570 NRC FIN No. A6256 INTERIM REPORT MG Research and Technic Assistanco gepag

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TECHNICAL EVALUATION REPORT ELECTRICAL, INSTRUMENTATION, AND CONTROL ASPECTS OF THE OVERRIDE OF CONTAINMENT PURGE VALVE ISOLATION AND OTHER SAFETY FEATURE SIGNALS DONALD C. COOK NUCLEAR PLANT UNIT NOS.1 AND 2 Docket Nos. 50-315 and 50-316 TAC Nos. 10170/10169 February 1980 A. C. Udy l

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ABSTRACT Several instances have been reported where the automatic closure of the containment ventilation or purge isolation valves would not have occurred because the safety actuation signals were manually overridden or blocked during normal plant operations. This report addresses elec-trical, instrumentation, and control design aspects for these valves, and the ability of the unit containment ventilation system to isolate on several diverse parameters. Other related systems were audited to the same guidelines.

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CONTENTS

1.0 INTRODUCTION

1 2.0 EVALUATION OF COOK NUCLEAR PLANT UNITS 1 AND 2.

2 2.1 Review Guidelines..

2 2.2 Containment Ventilation Isolation Circuits Design Description..

3 2.3 Containment Ventilation Isolation System Design Evaluation 4

2.4 Other Related Engineered Safety Feature System Circuits.

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3.0 CONCLUSION

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4.0 REFERENCES

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TECHNICAL EVALUATION REPORT ELECTRICAL, INSIRUMENTATION, AND CONTROL ASPECTS OF THE OVERRRIDE OF CONTAINMENT PURGE VALVE ISOLATION AND OTHER SAFETY FEATURE SICNALS DONALD C. COOK NUCLEAR PLANT UNIT NOS. 1 AND 2

1.0 INTRODUCTION

Based on the information supplied by Indiana & Michigan Power Company (I&MP), this report addresses the electrical, instrumentation, and control systems design aspects of the Containment Ventilation Iso-lation (CVI) subsystem of the Primary Containment Isolation (PCI) sys-t r

tem and other related Engineered Safety Feature (ESF) system functions for the Cook 1 and Cook 2 plants. The Final Safety Analysis Reports (FSARs) verify that these systema are identical in both plants.

Several instances have been reported where the automatic closure i

of the containment ventilation or purge isolation valves would not have occurred because the safety actuation signals were manually overridden or blocked during normal plant operations. These events resulted from procedural inadequacies, design deficiencies, and a lack of proper management controls. These events also brought into question the mech-anical operability of the valves themselves. These events were deter-mined by the Nuclear Regulatory Commission (NRC) to be an Abnormal Occurrence (#78-05) and accordingly, were reported to Congress.

f As a follow-up of this Abnormal Occurrence, the NRC is reviewing the electrical override aspects and the mechanical operability aspects of containment purging for all operating reactors.

On November 28, 1978, the NRC issued a letter, " Containment Purging During Normal Plant Operation" to all Boiling Water Reactor (BWR) and Pressurized Water Reactor (PWR) licensees.

I&MP responded to the letter in letters 2

3 4

dated January 4, 1979 and June 8,1979. A meeting was held on May 31, 1979 with I&MP and the NRC to clarify the design and character-istics of the Cook CVI and ESF systems.

I&MP declared that their interim modifications (see Reference 3) were permanent in a letter of I

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5 November 8, 1979.

Further discussion between I&MP and the NRC by 0

telephone conference occurred on November 16, 1979, resulting in a letter to the NRC on December 5, 1979.

2.0 EVALUATION OF COOK NUCLEAR PLANT UNITS 1 AND 2 2.1 Review Guidelines The intent of this evaluation is to determine if the following NRC requirements are met for the safety signals to all ESF equipment:

1.

Guideline No. 1--In keeping with the requirements of General Design Criteria 55 and 56. the over-ridinga of one type of safety actuation signal (e.g., radiation) should not cause the blocking of any other type of safety actuation signal (e.g.,

pressure) for those valves that have no function besides containment isolation.

2.

Guideline No. 2--Sufficient physical features (e.g.,

key lock switches) are to be provided to facilitate adequate administrative controls.

3.

Guideline No. 3--A system level annunciation of the overridden status should be provided for every safety system impacted when any override is active.

(See R.G. 1.47.)

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

1.

Guideline No. 4--Diverse signals should be provi/.ed to initiate isolation of the containment ventilation system.

Specifically, containment high radiation, safety injection actuation, and containment high l

pressure (where containment high pressure is not a l

pcrtion of safety injection actuation) should auto-matica11y initiate CVI.

The following definition is given for clarity of use in this a.

l evaluation:

Override:

the signal is still present, and it is blocked in order to perform a function contrary to the signal.

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2.

Guideline No. 5--The instrumentation and control systems provided to initiate the ESF should be designed and qualified as: safety grade equipment.

3.

Guideline No. 6--the overriding or resettinga og the ESF actuation signal should not cause any valve or damper to change position.

Guideline 6 in this review applies primarily to other related ESF systems because unplementation of this criterion for containment isola-tion will be reviewed by the Lessons Learned Task Force, based on the recommendations in NUREG-0578, Section 2.1.4.

When containment isola-tion is not involved, consideration on a case-by-case basis on automatic valve repositioning upon reset may be considered acceptable. Accept-ability would be dependent upon system function, design intent, and suitable operating procedures.

2.2 Containment Ventilation Isolation Circuits Design Description e

i Each of the Cook units has two ESF trains which close indepen-dently and separately the inboard and outboard PCI valves.

The valves can only be opened by manual control. Each valve has a three position, spring return to neutral center control switch. The control circuit requires manual operation of the switch to the "open" position for the valves to open. The automatic initiating signals which override any opening signal are listed below:

1.

Containment particulate activity, containment gaseous activity, or containment area monitor 3 radiation levels exceeding their setpoint will result in valve closure.

2.

A safety injection signal caused by either high containment pressure or low pressurizer pressure.

There are other safety injection actuation signals which will result in CVI, as well as Phase A of 7

Containment Isolation Signa 1.

The following definition is given for clarity of use in this a.

evaluation:

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Resets The signal has come and gone, and the circuit is being cleared in order to return it to the nonnal condition.

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e The CVI actuation signal resulting from the ESF initiation signal can be overridden f rom the ESF panel to allow manual opening of the CVI valves with the initiating signal still present.

The control system is such that the automatic closure signals will close the valves when the control switch is in the "open" position.

Loss of power to the control system or loss of air to the solenoid valve closes the isolation valves.

Valve position lights, open and closed, are provided on the control console.

Changes to the valve control circuitry were discussed with I&MP 3

and they responded with the following:

1.

Mechanical interference covers were provided for the reset switches, with " box car" type lead seals for the cover 2.

" Reset (Blocked)" annunciators were provided for the reset of each of the following ESF functions:

a.

Containment isolation--Phase A b.

Containment isolation--Phase B c.

"ontainment ventilation isolation (CVI) d.

Containment spray e.

Safety injection f.

Feedwater isolation 3.

A signal from the containment isolation--Phase A would initiate CVI valve closure regardless of the status of the CVI override.

2.3 Containment Ventilation Isolation System Design Evaluation i

Guideline 1 requires that no signal override can prevent another safety actuation signal from functioning.

The interim modification to provide a containment isolation Phase A signal to override any CVI signal override satisifies this guideline".

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Guideline 2 requires that reset and override switches have physi-cal provisions to aid in administrative control of the. switches. The momentary contact reset switches now have interference covers with " box car" type seals, thus complying with this guideline.

Guideline 3 requires that system level annunciation be provided for wherever an override affects the performance of a safety system.

The Cook units conform to this guideline, as a result of their interim modification".

Guideline 4 requires that isolation of the CVI system be actuated by several diverse signals. The CVI is actuated by diverse signals as reqired by this guideline, including an actuation signal from the safety inj ection sequencer. ~ Guideline 4 is satisfied.

Guideline 5 requires that isolation actuation signals be derived f rom safety grade equipment. The radiation signals to the CVI system are the only actuation signals that are not derived from safety grade equipment and, therefore, do not satisfy this guideline.

Guideline 6 requires that no resetting of isolation logic will, of itself, automatically open the isolation valves.

The Cook units con-form to this guideline in that the valve control switches require manual operation to open the valves after the isolation logic is reset.

2.4 Other Related Engineered Safety Feature System Circuits The CVI is the only portion of containment isolation where two signals were "0R"ed together to a common retentive memory with manual i

reset. This reset affects no other portions of containment isolation.

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i Reference 5 declares this modification to be permanent, and as such, a.

this guideline is satisfir.d.

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However, the Control Room Intake Duct Isolation Damper logic, while not a part of containment isolation, is of identical design to the CVI and is subject to the same failure mechanism that existed in the CVI.

It is recommended that this circuit be modified in a manner similar to what has been done for the CVI system.

No other manual overrides have been identified in the review of the material submitted for this audit.

3.0 CONCLUSION

S The electrical, instrumentation, and control design aspects of the containment ventilation isolation valves and other related ESF signals for the D. C. Cook station were evaluated using the design guidelines stated in Section 2.1 of this report. The D. C. Cook CVI complies with r

the review guidelines except for the radiation channels used to provide one of the diverse actuation signals. These radiation channels are not class 1E qualified equipment.

It is recommended that the NRC require

• i class 1E qualified radiation channels be used at the D. C. Cook station to actuate closure of the CVI valves.

It is also recommended that I&MP modify the logic for the Control Room Intake Duct Damper so that is is also in conformance with the review guidelines (see Section 2.1 of this report) as concluded in Section 2.4 of this report.

4.0 REFERENCES

1.

NRC/ DOR letter (A. Schwencer) to all BWR and PWR licensees, " Con-tainment Purging During Normal Plant Operation," dated November 28, 1978.

2.

I&MP letter (John Tillighast) to NRC (Harold R. Denton) Docket Nos. 50-315 and 50-316, " Containment Purging During Normal Plant Operation," January 4, 1979, AEP: NRC: 00114.

i I&MP letter (John E. Dolan) to NRC (Harold R. Denton) Docket Nos. 50-315 and 50-316, June 8, 1979, AEC: NRC: 00114A.

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4.

Meeting, NRC, IM&P, in Bethesda, MD, May 31, 1979, minutes issued June 12,1979 by Dave Wigginton, NRC.

5.

I&MP letter (John E. Dolen) to NRC (Harold R. Denton) Docket Nos. 50-315 and 50-316, November 8,1979, AEP: NRC: 00295.

6.

Telecon, Ray F. Scholl, Jr, NRC, Jude DelPercio and Tom King, I&MP, November 16, 1979, 2:30 p.m. EST.

7.

I&MP letter (John E. Dolen) to NRC (Harold R. Denton) Docket Nos. 50-315 and 50-316, December 5,1979, AEP: NRC: 00295A.

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