ML18046A628

Safety Evaluation Re Override of Containment Purge Isolation & Other Engineered Safety Feature Actuation Signals

ML18046A628
Person / Time
Site:	Palisades
Issue date:	05/06/1981
From:	Office of Nuclear Reactor Regulation
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ML18046A627	List: ML18046A626 ML18046A628
References
TASK-06-04, TASK-6-4, TASK-RR NUDOCS 8105130107
Download: ML18046A628 (7)

Text

Introduction SAFETY EVALUATION REPORT PALISADES PLANT OVtRRIDE OF CONTAINMENT PURGE ISOLATION ANO OTHER ENGINEERED SAFETY FEATURE ACTUATION SIGNALS ENCLOSURE As a result of Abnormal Occurrence #78-5, the NRC issued a generic letter requesting each licensee to take certain actions.

Evaluation The enclosed report was prepared for us by EG&G, Idaho, as part of our technical assistance program for SEP.

This report provides a technical evaluation of the electrical instrumentation and control design aspects of the override of containment purge valves isolation and other engineered safety feature actuation signals and is based upon review of these design aspects against the six NRC criteria provided for the review.

The technical evaluation concludes that with one exception, the modifications made by the licensee at the plant have brought the designs into conformance with our review criteria. The one exception is that a safety injection actuation signal does not initiate containment purge and ventilation system isolation.

At Palisades, all of the containment atmcsphere lines are blanked off during plant power operations except for.the 12 inch air rooms purge supply.

lhe licensee, in response to NUREG-0737, has committed to make the following changes in the circuitry for this 12. inch line.

Valves CV-1813 and 1814 on the air supply line to t.he air room are normally closed; however, there is no mechanical device to administratively seal the valves closed.

Procurement of key lock switches to seal these valves closed is now in process.

Once these key lock switches become avaflable, they will be installed at the first subsequent cold shutdown of the plant.

In the interim, links will be opened and tagged to de-energize the power to the hand switches so that these valves cannot be opened.

Valves CV-1813 and 1814 are not now included but will be added to M0-29.

{The containment purge valves are verified to be closed at least every 31 days by Technical Specifications Surveillance Program P,rocedure M0-29.)

Conclusion Based upon our review of the consultant's technical evaluation, we conclude that the electrical, instrumentation and control design aspects of the override of containment purge valves isolation and other engineered safety feature actuation signals are acceptable.

s 1 os-1sot01

SEP TECHNICAL EVALUATION

. TOPIC VI-4

• e ELECTRICAL, INSTRUMENTATION, AND CONTROL ASPECTS OF THE OVERRIDE OF CONTAINMENT PURGE VALVE ISOLATION FINAL DRAFT PALI SAD ES PLANT Docket No. 50-255 April 1981 A. C. Udy Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.

0286J 4-29-81

CONTENTS 1

• 0 I :HR OD UC TION * * * * * * * * * * *

• 2.0 EVALUATION OF THE PALISADES PLANT

2. 1 Review Guidelines...

2.2 Containment Ven ti 1 a ti on Isolation Circuits ~esi gn Description...................

2.3 Containment Vent i 1 a tion !sol ation System Design Evaluation...................

2.4 Other Related Engineered Safety Feature System Circuits 3.0

SUMMARY

4. 0 RE FERENC ES

• i i 1

• 1

.. 2 3

.. 3 4

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SEP TECHNICAL EVALUATION TOPIC VI -4 ELECTRICAL, INSTRUMENTATION, AND CONTROL ASPECTS OF

• THE OVERRRIDE OF COIHAINMElH PURGE VALVE ISOLATION PALISADES PLANT 1.0 INTRODLCTIOtJ Based on the infonnation supplied by the Consumer.s Power Company {CP) this report addresses the electrical, instrumentation, and control systems design aspects of the Containment Ventilation Isolation (CV!) system.

Several instances have been reported where the automatic closure of

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~~e containment ventilation or purge isolation valves would not have occur-red because the safety actuation signals were manually overridden or blocked during nonna 1 pl ant operations.

Lack of proper management contra 1 s, pro-cedural inadequacies, and circuit design deficiencies contributed to these instances.

These events also brought into question the mechanical oper-ability of the valv&S themselves.

These events were detennined by the Nuclear Regulatory Commission (NRC) to be an Abnonnal Occurrence (#78-05) and accordingly, were reported to Congress.

T11e NRC is now re viewing the electrical *override aspects of containment purging and venting for all operating reactors.

On November 28, 1978, t~e NRC issued a letter, "Containment Purging During Nonnal Plant Operation" to all Boiling Water Reactor and Pressurized Water Re!}ctor li.censees," which required a review2of these systemj by the licensee.

~P responded on December 28, 1978, March 1, 1979, and July 14, 1980. The Final Safety Analysis Report (FSAR) also contains design infonnation reviewed for this report.

2.0 EVALUATION OF THE PALISADES PLANT 2.1 Review Guidelines The intent of this evaluation is to detennine if the actuating signals

-for the CV! system meet the following NRC requirements:

1.

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

a.

The following d~finitions are given for clarity of use in this evaluation:

• Overrride:

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

l

any other type of safety actuation signal (e.g., pres-sure) for those valves that have no function besides containment isolation.

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

key 1 ock sl'li tche s) a re to be provided to f aci 1 i tate 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.

Additionally, this review uses the following NRC design guidelines:.

1.

Guideline No. 4--Divers.e signals should be provided to initiate isolation of the containment ventilation system. Specifically, containment high radiation, safety injection actuation, and containment high pres-sure (where containment high pressure is not a portion of safety injection actuation) should automatically initiate CVI.

2.

Guideline No. 5--Tile 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 of the

. ESF actuati ori signal should not cause any valve or damper to change position.

2.2 Containment Ventilation Isolation Circuits Design Description Automatic closure of containment pu4ge ~nd vent isolation valves will occur on any of the following conditions : *

1.

High containment pressure

2.

High containment radiation.

CP has indicated that these signals are derived from safety grade equipment.

Tile control of the solenoid-operated purge and vent valves use main-

• tained position control switches.* Relay interlocks require these switches

, to be returned to the closed position after an isolation signal before the valve can be re-opened.

Valve position lights show the actual valve posi-tion.

Tile solenoid valves fail closed on loss of air or on loss of power~

a.

The following definitions are given for clarity of use in this evaluation:

Reset:

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

2

Tne override of the CVI valves automatic closure can only be done by use of jumpers. 4 The CVI valve control *circuits have been modified4 to prevent changing position dh reset of the actuatio~ signal. Resetting qf the actu-ation signal is by depressing a protected (by an open ring guard) pushbutton switch.

Pressing this switch while the actuating condition is present has no effect of the actuation signal.

2.3 Containment Ventilation Isolation System Design Evaluation Guideline l requires that no signal override can prevent another safety actuation signal from functioning.

The Palisades plant has no provision for overriding the actuation signals which cause isolation of the CVI valves.

lhe Palisades plant is in conformance with this guideline.

Guideline 2 requires that reset and override switches have physical provisions to aid in the administrative control of these switches. lhere are no override switches.

The reset switches are protected b~ a ring guard and a re of no effect if the actuation signal is still present

• This guideline is satisfied.

Guideline 3 requires system level annunciation whenever an override affects the performance of a safety system.

In the CP review of other safety actuation signals, they state that sys~em level annunciation is provided for every override at the Palisades plant. This is in confonnance with this NRC guideline.

Guideline 4 requires that isolation of the CVI valves be actuated by several diverse signals. lhis requirement is not met in that only:

1.

High pressure in the reactor building will initiate isolation

2.

High-level radiation trips will initiate isolation.

Safety injection actuation will not initiate isolation.

Guideline 5 requires that isolation actuation signals be derived from safety gradg equipment.* The Palisades plant meets this requirement.

Guideline 6 requires that no reset of isolation logic will, of itself, automatica 11 y open the i sol at ion valves.

The Pali sades pl ant* now* complys with this guideline.

2. 4 Other Related Engineered Safety Feature System Circuits A review of other related ESF circuits was also made.

No other manual overrides have been identified in the review of the.materi a 1 submitted for this audit.

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,,*.I 3.0

SUMMARY

The NRC issued a letter, "Containment Purging During Nonnal Plant Operation," 1'lhich requested CP to review purging requirements, controls, and procedures for purging at the Pali sades pl ant.

i Tne electrical, instrumentation, and control design aspects of the

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containment ventilation isolation valves for Palisades plant i'lere evaluated-using the design gudelines stated in Section 2.1 of this report.

These guidelines are satisfied except that a safety injection will not cause the CVI system to isolate containment.

The NRC should, in its integrated assessment of the Palisades plant, require that this deficiency be corrected.

4.0 REFEREM:ES

1.

NRC/DOR letter (A. Schwencer) to CP&L and all BWR and PWR licensees, "Containment Purging During Nonnal Plant Operation, 11 dated t-k>vember 28, 197 8.

2.

CP 1 etter_, D. P. Hoffman, to Director, Nuclear Reactor Regulation, U.S. NRC, "Containment Purging During Nonnal Plant Operation",_

December 28, 1978.

3.

CP letter, D. P. Hoffman, to Director, Nuclear Reactor Regulation, U.S. NRC, "Containment Purging During ~lonnal Plant Operation",

March 1, 1979.

4.

CP letter, D. P. Hoffman, to Director, Nuclear Reactor Regulation,

u. S. NRC, "Response to SEP Topic VI-4--Containment Isolation System, 11 July-14, 1980.

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