Information Notice 1985-51, Inadvertent Loss or Improper Actuation of Safety-Related Equipment

Inadvertent Loss or Improper Actuation of Safety-Related Equipment

ML031180241
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	07/10/1985
From:	Jordan E NRC/IE
To:
References
IN-85-051, NUDOCS 8507090268
Download: ML031180241 (6)

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SSINS No.: 6835 IN 85-51 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 July 10, 1985 IE INFORMATION NOTICE NO. 85-51: INADVERTENT LOSS OR IMPROPER ACTUATION

OF SAFETY-RELATED EQUIPMENT

Addressees

All nuclear power reactor facilities holding an operating license (OL) or a

construction permit (CP).

Purpose

This information notice is provided to alert licensees of potentially signifi- cant reactor safety problems that may be a byproduct of the normal practice of

removing fuses or of opening circuit breakers for personnel protection during

maintenance and plant modification activities. The reactor safety concern may

result when the effects of electrical power interruption on all circuits

powered by the fuse or breaker are not fully reviewed in advance. Errors in

the review have resulted in unknowingly disabling safety systems and also have

caused inadvertent actuation of safety systems. It is suggested that recipi- ents review this information for applicability to their facilities and consider

actions, if appropriate, to preclude similar problems at their facilities.

However, suggestions contained in this information notice do not constitute NRC

requirements; therefore, no specific action or written response is required.

Description of Circumstances

At Susquehanna Unit 2 on July 9, 1984 with the plant at approximately 20% of

full power electricians removed two dc-control power fuses for personnel

protection during modifications involving the core spray isolation logic. The

electricians believed that removing these fuses would provide the nearest local

blocking-point protection needed while performing the modification. However, the fuses that were removed were considerably "upstream" of the local blocking

point and the following situations resulted from this improper action:

1. Signals to start the pumps and position valves for the A loop of the core

spray system were lost.

2. One of the diesel generators would not have received a "Start" signal from

the Division 1 core spray logic that is provided for a loss-of-coolant

accident (LOCA) condition associated with Unit 2.

8507090268

IN 85-51 July 10, 1985 3. The A and C instrumentation channels, sensing reactor water level and

drywell pressure, were made inoperable. Because of this, the residual

heat removal system and high pressure injection system would not have

received an actuation signal from those channels in the event of an

accident. However, the B and D channels remained functional.

4. A partial isolation signal for drywell cooling was generated.

5. The load shedding feature of the A and C 4160 V ac essential buses associ- ated with Units 1 and 2 were disabled, and the instrument air compressors

for Unit 2 would not have tripped if a LOCA condition had existed for Unit

2.

As a result of this event, the licensee instituted training sessions for

personnel. The training sessions emphasized review and analysis of the cir- cuits involved in all current and future construction work orders at the

Susquehanna facility and included a human factors analysis focusing on the

adequacy of the status switch features for the core spray system and other

safety-related systems.

Discussion:

Following the event at Susquehanna Unit 2, the NRC conducted a search for other

licensee event reports (LERs) from 1981 through 1984 that had similar cause and

effect. This search resulted in the identification of five additional events

which may be indicative that the problem is widespread. The events described

in these reports are briefly summarized in Attachment 1. The event described

above and those summarized in Attachment 1 illustrate how the practice of

removing fuses may result in actuation or disabling of safety-related equipment

during any mode of plant operation. At the time the fuses were removed, the

involved plant personnel were unaware of the resulting actuation and

inoperabilities. Similar situations could occur when electrical circuits are

de-energized by operating circuit breakers for personnel protection.

The practice of de-energizing circuitry in order to provide plant personnel

with appropriate protection is unavoidable. Corrective and preventive actions.

by licensees have emphasized the following items: identification of effects on

plant equipment or systems, independent verification of the evaluation of

effects, and utilization of the nearest local fuse or circuit breaker to

minimize the number of systems affected.

IN 85-51 July 10, 1985 No-specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

d~r an,dDirector

Division Emergency Preparedness

and Eng eering Response

Office of nspection and Enforcement

V. D. Thomas, IE

(301) 492-4755 Attachments:

1. Earlier Events Similar to the One at Susquehanna

2. List of Recently Issued IE Information Notices

Attachment 1 IN 85-51 July 10, 1985 EARLIER EVENTS SIMILAR IN NATURE TO THE ONE

AT SUSQUEHANNA

Surry Station, September 1981

In this event, an electrician was attempting to remove a battery in the plant's

smoke,detector system. The electrician did not wish to leave energized wiring

exposed and therefore he removed a line fuse. This action disabled the smoke

detector panel that provides early detection of fires, thereby introducing the

potential for damage of safety-related equipment.

The licensee attributed the cause of this event to personnel error in that the

electrician did not realize that removing the line fuse would disable the smoke

detector panel. Corrective action taken to prevent recurrence of this event

was to revise the labeling of the smoke detector battery chargers and associat- ed circuit panels with a caution tag.

Oyster Creek Station, December 1981

While performing maintenance activities to repair a faulty electromatic relief

valve pressure switch, dc-control power fuses were removed, resulting in the

inoperability of one trip system in the automatic depressurization system

(ADS). The licensee reported that the cause of the loss of ADS trip system

redundancy was the removal of the power fuses by plant personnel, without

realizing the consequences on the ADS control logic circuitry. However, had a

plant condition been present that required the operation of the ADS, the

redundant trip system would have actuated the four remaining relief valves to

depressurize the reactor system.

To prevent recurrence of this reportable occurrence, the licensee incorporated

it in the required reading program for Shift Operations Supervisors and Instru- ment Department Personnel. Additionally, the power fuses that defeat the

redundancy of the ADS have been identified with a warning label.

Sequoyah Unit 1, September 1982

This licensee reported that during modifications to train "B" of the

solid-state protection system (SSPS), the power fuses were removed to facili- tate work on the output relays. This caused the train "B" reactor heat removal

(RHR) suction valve to close rendering that system inoperable. A review of the

drawings associated with the SSPS showed that the power supply to the output

relays also supplied power to a relay that operates the RHR suction valve.

When this relay is de-energized, the valve automatically closes. The operator

immediately returned the system to normal operating conditions.

A change was made to the facility work plan covering SSPS modification to

inform operators that removal of the power fuses isolates the associated train

of the RHR suction valve. The licensee also reports that caution signs were

placed near the location of the fuses in the SSPS cabinets.

Attachment 1 IN 85-51 July 10, 1985 Diablo Canyon Unit 1, May 1983 The event at Diablo Canyon Unit 1 during May 1983 was similar to the events

discussed above, in that personnel at the plant removed power fuses to perform

work activity. This action resulted in disabling of radiation monitoring

equipment.

To prevent recurrence, plant personnel have been instructed to ensure that a-l

effects on plant equipment are known and recognized before approving clearances

for work activity.

Susquehanna Unit 1, April 1984

This earlier event at Susquehanna Unit 1 also was caused by removing power

fuses for personnel protection. Plant personnel removed two fuses associated

with the primary containment isolation logic for Unit 2 to perform a modifica- tion for the logic circuitry. This resulted in the actuation of a false high

drywell pressure signal, which, in turn, actuated the common control room

emergency outside air supply and standby gas treatment systems. The licensee

later discovered that an improperly placed wire jumper in conjunction with fuse

removal actually caused the false actuation. Subsequently, the wire jumper was

installed properly.

To prevent recurrence of this event, the subject work activity and associated

wiring error were reviewed with the work crew involved. During this review the

licensee also instructed personnel to review and verify circuitry before

de-energizing power sources to equipment scheduled for maintenance or

modification.

Attachment 2 IN 85-51 July 10, 1985 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

85-50 Complete Loss Of Main And 7/8/85 All power reactor

Auxiliary Feedwater At A PWR facilities holding

Designed By Babcock & Wilcox an OL or CP

I

85-49 Relay Calibration Problem 7/1/85 All power reactor

facilities holding

an OL or CP

85-48 Respirator Users Notice: 6/19/85 All power reactor

Defective Self-Contained facilities holding

Breathing Apparatus Air an OL or CP, research, Cylinders and test reactor, fuel cycle and

Priority 1 material

licensees

85-47 Potential Effect Of Line- 6/18/85 All power reactor

Induced Vibration On Certain facilities holding

Target Rock Solenoid-Operated an OL or-CP

Valves

85-46 Clarification Of Several 6/10/85 All power reactor

Aspects Of Removable Radio- facilities holding

active Surface Contamination an OL

Limits For Transport Packages

85-45 Potential Seismic Interaction 6/6/85 All power reactor

Involving The Movable In-Core facilities holding

Flux Mapping System Used In an OL or CP

Westinghouse Designed Plants

85-44 Emergency Communication 5/30/85 All power reactor

System Monthly Test facilities holding

an OL

85-43 Radiography Events At Power 5/30/85 All power reactor

Reactors facilities holding

an OL or CP

OL = Operating License

CP = Construction Permit