Information Notice 1995-15, Inadequate Logic Testing of Safety-Related Circuits

Inadequate Logic Testing of Safety-Related Circuits

ML031060316
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, 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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	03/07/1995
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-95-015, NUDOCS 9503010381
Download: ML031060316 (8)

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

March 7, 1995

NRC INFORMATION NOTICE 95-15:

INADEQUATE LOGIC TESTING OF SAFETY-RELATED

CIRCUITS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to logic testing methods that may not completely

test the functionality of a safety-related control circuit.

It is expected

that recipients will review the information for applicability to their

facilities and consider actions, as appropriate, to avoid similar problems.

However, suggestions contained in this information notice are not NRC

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

Description of Circumstances

The following logic system functional testing deficiencies have been reported

recently and serve as examples of inadequate surveillance testing.

Cooper Nuclear Station

On May 23, 1994, during review of test procedures for automatic load shedding, the licensee determined that load shedding of nonsafety loads from safety- related electrical buses was not being verified.

In addition to five

nonsafety-related motor control centers, the load shed capability of the

service water booster pumps, the station air compressors, and the control rod

drive pumps was not verified. As a result, both emergency diesel generators

were declared inoperable, the licensee declared an Unusual Event, and the

reactor was shut down.

Fermi 2 On July 15, 1994, the licensee discovered that the permissive interlocks for

the 4160-Vac emergency bus undervoltage relays were not being adequately

tested. While the reviewing engineer was verifying that proper test overlap

existed between an electrical logic functional test procedure and a related

instrumentation and control (I&C) logic functional test procedure for the

residual heat removal system, he determined that neither the electrical

procedure nor the I&C procedure fully tested the pump logic.

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IN 95-15 March 7, 1995 Neither procedure included testing of the conductors that connected the

electrical and the I&C portions of the circuit. Additionally, verification

that a switchgear circuit breaker would not close following initiation of an

undervoltage relay was not included in the procedure.

Waterford 3 On September 7, 1994, the licensee discovered that surveillance test

procedures did not adequately verify that safety-related 4160-Vac and 480-Vac

electrical buses designed to swap from one power source to another ("swing"

buses) would properly deenergize and subsequently automatically realign to

the proper source.

Before performing the integrated emergency diesel

generator testing, the swing buses were routinely aligned to the electrical

division not under test.

A licensee investigative team concluded that the swing buses may have been

deleted from the preoperational test procedure because of a misunderstanding

of what constituted a "permanently connected load" in their technical

specifications.

Although the swing buses can be aligned to more than one

power source, the transfer from one source to another requires that the buses

be momentarily deenergized (a "dead bus" transfer) and therefore should be

considered permanently connected loads.

The licensee subsequently revised the

definition of a permanently connected load in the technical specification

bases.

Grand Gulf Nuclear Station

On September 29, 1994, during a review of logic system functional testing

overlap, the licensee discovered that one of four sets of contacts in the "B"

containment spray train high drywell pressure initiation logic was not being

verified to function during testing.

Because of a difference in logic between

the "A" and "B" trains, the manual initiation pushbutton had to be held in

while the trip signal was introduced in the "B" train logic.

Holding the

pushbutton in created a current path that bypassed one set of contacts, and

these contacts were not tested elsewhere in the procedure.

Arkansas Nuclear One, Unit 2 (ANO-2)

On October 7, 1994, in response to a query about logic system functional

testing from the NRC senior resident inspector, the licensee discovered that

the swing high-pressure safety injection pump actuation logic was not being

fully tested under the engineered safety features surveillance test procedure.

The swing pump safety injection actuation signal was not being verified when

the pump was being powered from either emergency diesel generator. Further

review of the service water pump surveillance methodology found that

individual contacts in the engineered safety feature starting circuitry also

were not being tested.

These contacts prevent redundant service water pumps

from automatically starting and loading onto a 4160-Vac bus being powered by a

diesel generator to ensure that the diesel is not overloaded.

IN 95-15 March 7, 1995 Arkansas Nuclear One, Unit 1 (ANO-1)

On October 8, 1994, the licensee performed a review of engineered safety

feature testing methodology as a result of concerns raised during operation of

ANO-2 and discovered two discrepancies. The licensee found that integrated

testing of the high-pressure injection pumps did not include complete

verification of the circuit breaker position interlocks used in the pump auto- start circuitry.

Also, integrated testing did not verify that the swing high

pressure injection pump would start if the logic path containing the normal

feeder breaker contact was used. Review of the service water system showed

that the automatic restart logic for the service water pumps is not verified

for the condition when power is supplied from the offsite feeder breaker.

Discussion

Because testing of the engineered safety feature logic is performed during

reactor operation when actuation of the system under test would be

undesirable, the logic test must be broken up into parts so that the system

does not actuate.

To ensure that no part of the logic is overlooked, the

procedures for these partial functional tests must assure an overlap between

where one section of testing ends and the next section begins.

Inadequate logic system functional testing of safety-related circuits has been

the topic of numerous information notices issued by the NRC, but licensees

continue to report instances in which a particular component or section of

logic has not been included in the testing. The complexity of some of these

circuits, combined with a lack of understanding of the depth of the review

required to verify the testing overlap, has resulted in continuing occurrences

of inadequate test scope.

Related Generic Communications

Information Notice 93-38, "Inadequate Testing of Engineered Safety Features

Actuation Systems," was issued on May 24, 1993, to alert licensees to

inadequate testing of engineered safety feature actuation systems.

Information Notice 92-40, "Inadequate Testing of Emergency Bus Undervoltage

Logic Circuitry," was issued on May 27, 1992, to alert licensees to a test

method that failed to verify the capability of undervoltage logic circuitry to

deenergize safety-related buses, thus preventing an emergency diesel generator

from closing onto the bus.

Information Notice 88-83, "Inadequate Testing of Relay Contacts in Safety- Related Logic Systems," was issued on October 19, 1988, to alert licensees to

inadequate testing of relay contacts in safety-related logic systems.

Attachment

IN 95-15

March 7, 1995 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

- -

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4. -

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Information

Notice No.

Subject

suane I

Issuance

Issued to

95-14

95-13

95-12

95-11 Susceptibility of Con- tainment Sump Recircula- tion Gate Valves to

Pressure Locking

Potential for Data

Collection Equipment to

Affect Protection System

Performance

Potentially Nonconforming

Fasteners Supplied by

A&G Engineering II, Inc.

Failure of Condensate

Piping Because of Erosion/

Corrosion at a Flow-

Straightening Device

Potential for Loss of

Automatic Engineered

Safety Features

Actuation

Potential for Loss of

Automatic Engineered

Safety Features

Actuation

Use of Inappropriate

Guidelines and Criteria

for Nuclear Piping and

Pipe Support Evaluation

and Design

Inaccurate Data Obtained

with Clamp-On Ultrasonic

Flow Measurement Instruments

02/28/95

02/24/95

02/21/95

02/24/95

02/10/95

02/03/95

01/31/95

01/30/95

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

95-10

Supp. 1

95-10

95-09

95-08 OL = Operating License

CP = Construction Permit

IN 95-15 March 7, 1995 This information notice requires no specific action or written response.

If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Hukam Garg, NRR

(301) 415-2929

David Skeen, NRR

(301) 415-1174 Attachment:

List of Recently Issued NRC Information Notices

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IN 95-15 March 7, 1995 This information notice requires no specific action or written response.

If

you have any questions About the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Original signed by

Brian K. Grimes

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts:

Hukam

(301)

Garg, NRR

415-2929 David

(301)

Skeen, NRR

415-1174 Attachment:

List of Recently Issued NRC Information Notices

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OFFICIAL RECORD COPY

IN 95-XX

February XX, 1995

This information notice requires no specific action or written response.

If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts:

Hukam Garg, NRR

(301) 415-2929 David

(301)

Skeen, NRR

415-1174 Attachment:

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February XX, 1995

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of 4peratVng Reatkw Support

Office of Nuclear Reactor Regulation

Technical contacts:

Hukam Garg, NRR

(301) 415-2929 David

(301)

Skeen, NRR

415-1174 Attachment:

List of Recently Issued NRC Information Notices

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