Information Notice 1993-15, Failure to Verify the Continuity of Shunt Trip Attachment Contacts in Manual Safety Injection and Reactor Trip Switches

Failure to Verify the Continuity of Shunt Trip Attachment Contacts in Manual Safety Injection and Reactor Trip Switches

ML031080143
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, Maine Yankee, Quad Cities, 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
Issue date:	02/18/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-015, NUDOCS 9302120058
Download: ML031080143 (15)

UNITED SIATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 February 18, 1993 NRC INFORMATION NOTICE 93-15: FAILURE TO VERIFY THE CONTINUITY OF SHUNT TRIP

ATTACHMENT

CONTACT

S IN MANUAL SAFETY INJECTION

AND REACTOR TRIP SWITCHES

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 a surveillance test method that is not adequate

to verify the operability of the contacts in manually operated safety

injection and reactor trip switches. 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

On May 19, 1992, the Houston Lighting and Power Company, the licensee for the

South Texas Project, issued a notification of an unusual event and began a

technical specification-required shutdown of both units. The licensee had

discovered that it was not conducting adequate testing of the switch contacts

that directly actuate the shunt trip attachment of the reactor trip circuit

breakers. These initiation contacts are actuated by either the manual safety

injection or reactor trip switches and are the means by which operator action

directly actuates the shunt trip, one of two means by which the breaker is

tripped, the other being the undervoltage trip.

The licensee had been performing surveillance tests of the safety injection

switches and the reactor trip switches without opening the associated block

switch (see attached simplified diagram of the manual reactor trip circuitry).

If not opened, the block switch allows the same manual switch contacts that

actuate the undervoltage attachment to indirectly actuate the shunt trip

attachment. Therefore, the manual switch contacts which directly actuate the

shunt trip attachment are not necessary for actuation of the shunt trip and, therefore, not independently verified as operable. This surveillance

inadequacy has also been identified at the Callaway Plant, the Seabrook

Nuclear Station, and the Wolf Creek Generating Station. The above mentioned

licensees have since properly verified the operability of the manual switch

contacts.

9302120058 po4OtG Ltt 9j3 'S7 o(

Age 2&//45 V csC'

IN 93-15 February 18, 1993 Discussion

There are two manually operated safety injection switches and two manually

operated reactor trip switches. Each switch contains circuitry which is

designed to initiate a reactor trip. The attached diagram illustrates the

manner by which a reactor trip breaker is opened when any of the manual

switches is engaged. When a switch is operated, moveable contacts in that

switch change state. For example, when safety injection switch designated SI1 is engaged, the SIl contacts in the 48 Vdc circuit open and S11 contacts in

the 125 Vdc circuit close. The opened 48 Vdc S11 contacts interrupt power to

the undervoltage trip coil (UV) of the undervoltage trip attachment.

Concurrently, the closed S11 contacts in the 125 Vdc circuit allow the shunt

trip coil (STC) of the shunt trip attachment to become energized.

De-energizing the UV causes the armature of the undervoltage trip attachment

to make contact with and lift the trip lever of the associated reactor trip

breaker. Energizing the STC causes the shunt trip attachment armature to also

make contact with and lift the trip bar of the associated reactor trip

breaker. As a result of either of these actions, the circuit breaker opens to

initiate a reactor trip.

Opening of the SI1 contacts in the 48 Vdc circuit also de-energizes the auto

shunt trip relay (STA) causing the associated STA contacts in the 125 Vdc

,-'circuit to close. The closed STA contacts provide an electrical path by which

the STC is energized, thus actuating the shunt trip attachment. This path is

in parallel to the electrical path provided by the closed 125 Vdc S11 contacts

when the switches are actuated.

The licensee corrected their procedure as follows:

During continuity tests of the 125 Vdc SI1 contacts, the block switch

that is shown in series with the STA contacts is held in the open

position. This action assures that the voltage measured at the terminal

block of the reactor trip breaker results solely from the closure of the

125 Vdc S11 contacts and not from the closed STA contacts. If the "block

switch' is not held in the open position, it is not possible to

independently verify the continuity of the 125 Vdc SIl contacts.

Continuity checks of the 125 Vdc contacts in the other manually operated

switches are made in the same way.

Related Generic Communication

On May 23, 1985, the NRC issued Generic Letter 85-09 which described an

appropriate methodology for verifying the operability of moveable contacts in

the manual switches.

IN 93-15 February 18, 1993 This information notice requires no specific action or written response. If

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train

2. List of Recently Issued NRC Information Notices

AUTO/MANUAL REACTOR TRIP CIRCUIT

TYPICAL TRAIN

(

125V DC

NOTE:

UV: UNDERVOLTAGE TRIP COIL

STC: SHUNT TRIP COIL

ALL Sl

CONTACT

S OPERATE SIMULTANEOUSLY

ALL S12

CONTACT

S OPERATE SIMULTANEOUSLY I-I

ALL HS1

CONTACT

S OPERATE SIMULTANEOUSLY 'I J. im

ALL HS2

CONTACT

'STA' CLOSES WHEN RELAY 'STA' DE-ENERGIZES

Xittachment 2 IN 93-15 February 18, 1993 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

93-14 Clarification of 02/18/93 All licensees who possess

10 CFR 40.22, Small source material.

Quantities of Source

Material

93-13 Undetected Modification 02/16/93 All holders of OLs or CPs

of Flow Characteristics for nuclear power reactors.

in the High Pressure

Safety Injection System

93-12 Off-Gassing in Auxiliary 02/11/93 All holders of OLs or CPs

Feedwater System Raw for nuclear power reactors.

Water Sources

93-11 Single Failure Vulner- 02/04/93 All holders of OLs or CPs

ability of Engineered for nuclear power reactors.

Safety Features

Actuation Systems

93-10 Dose Calibrator Quality 02/02/93 All Nuclear Regulatory Com- Control mission medical licensees.

93-09 Failure of Undervoltage 02/02/93 All holders of OLs or CPs

Trip Attachment on for nuclear power reactors.

Westinghouse Model DB-50

Reactor Trip Breaker

93-08 Failure of Residual 02/01/93 All holders of OLs or CPs

Heat Removal Pump for nuclear power reactors.

Bearings due to High

Thrust Loading

93-07 Classification of Trans- 02/01/93 All Licensees required to

portation Emergencies have an emergency plan.

93-06 Potential Bypass Leak- 01/22/93 All holders of OLs or CPs

age Paths Around Filters for nuclear power reactors.

Installed in Ventilation

Systems

OL = Operating License

CP = Construction Permit

IN 93-15 February 18, 1993 This information notice requires no specific action or written response. If

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Onginal signed by

Brian K. Grimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DORS ASC/OEAB:DORS ADM:RPB SICB:DST

NFields* AGautam* JMain* SNewberry*

02/08/93 09/24/92 09/18/92 10/05/92 SC/OEAB: DORS C/OEAB:DORS C/OGCB:DORS D/DRCH

EGoodwin* AChaffee* GMarcus* BBoger*

01/15/93 11/10/92 11/19/92 01/21/93 02/lzz93

02/05/93 DOCUMENT NAME: 93-15.IN

IN 93-XX

January xx, 1993 This information notice requires no specific action or written response. If

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DOR~S ASC/OEAB:DORS ADM:RPB SICB:DST

NFields PI AGautam* JMain* SNewberry*

- /. /93 09/24/92 09/18/92 10/05/92 SC/OEAB:DORS C/OEAB:DORS C/OGCB:DORS D/DRCH D/DORS

EGoodwin* AChaffee* GMarcus* BBoger* BGrimes

01/15/93 11/10/92 11/19/92 01/21/93 / /9A

02/05/93 DOCUMENT NAME: G:\ENF\INSTP.REV

_ 7

IN 93-XX

January xx, 1993 This information notice requires no specific action or written response. If

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DORS ASC/OEAB:DORS ADM: RPB SICB:DST

NFields 16 AGautam* JMain* SNewberry*

1 * /17193V) 09/24/92 09/18/92 10/05/92 SC/OEAB:DORS C/OEAB:DORS C/OGCB:DORS D/D D/DORS

EGoodwin AChaffee* Ye GMarcus* BGrimes

I /5793 ':S 11/10/92 8 11/19/92 / /1/ 93 / /93 f /S/qAt

ar lr>l

DOCUMENT NAME: G:\ENF\INSTP,(

IN 92-XX

December xx, 1992 If

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

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DORS ASC/OEAB:DORS ADM:RPB SICB:DST

NFields* AGautam* JMain* SNewberry*

09/22/92 09/24/92 09/18/92 10/05/92 C/OEAB:DORS C/OGCB:DORS D/DORS

AChaffee* GMarcus* #BGrimes

11/10/92 11/19/92 / /92 DOCUMENT NAME: G:\ENF\INSTP

IN 92-XX

November xx, 1992 contacts to close and automatically energize the coil of the shunt trip

attachment in the 125 Vdc circuit.

When either the manual SI (HSI) or reactor trip switch (HS2) is engaged, all

respective contacts in each switch change state. When voltage measurements

are taken at the terminal block of-the RTB-tarverify the continuity of the 125 Vdc contacts in the manual switches, the "block switch" must be held in the

open position when either switch is engaged to the trip position. If the

"block switch" is not held in the open position, it is not possible to

independently verify the continuity of the switch contacts since the "STAB

contacts will close and provide a parallel path to energize the shunt trip

attachment.

On May 23, 1985, the NRC issued GenerictetteEr85-09 which described the

appropriate methodology for verifying the operability of contacts in the

manual switches.

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

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173.

Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train S Diagram

2. List of Recently Issued NRC Infor'4 ation Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DORS ASC/OEAB:DORS ADM:RPB SICB:DST

NFields* AGautam* JMain* SNewberry*

09/22/92 09/24/92 09/18/92 10/05/92 C/OEAB:DORS C/OGCB: S D/DORS

AChaffee* G arcusn5 BGrimesot

11/10/92 ///9/92 0." / /92 DOCUMENT NAME: G:\ENF\IN STEXA.ENF

IN 92-XX

November xx, 1992 safety injection switches de-energize the undervoltage trip attachment and the

auto shunt trip relay. De-energizing the auto shunt trip relay causes the STA

contacts to close and automatically energize the coil of the shunt trip

attachment.

When either the manual SI (HS1) or reactor trip switch (HS2) is engaged, all

respective contacts in each switch change state. When voltage measurements

are taken at the terminal block of the RTB to verify the continuity of the 125 Vdc contacts in the manual switches, the "block switch" must be held in the

open position when either switch is engaged to the trip position. If the

"block switch" is not held in the open position, it is not possible to

independently verify the continuity of the switch contacts since the "STA"

contacts will close and provide a parallel path to energize the shunt trip

attachment.

On May 23, 1985, the NRC issued Generic Letter 85-09 which described the

appropriate methodology for verifying the operability of contacts in the

manual switches.

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

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train S Diagram

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DORS ASC/OEAB:DORS ADM:RPB SICB:DST

NFields* AGautam* JMain* SNewberry*

09/22/92 09/24/92 09/18/92 10/05/92 C/ &RDORS C/OGCB:DORS D/DORS

AC i'ffee GMarcus BGrimes

it /w/ 9 2 / /92,2'9' / /92 DOCUMENT NAME: G:\ENF\INSTEXA.ENF

IN 92-XX

October xx, 1992 safety injection switches deenergize the undervoltage trip attachment and the

auto shunt trip relay. Deenergizing the auto shunt trip relay causes the STA

contacts to close and automatically energize the coil of the shunt trip

attachment.

When either the manual SI or reactor trip switch is engaged, all respective

contacts in each switch change state. When voltage measurements are taken at

the terminal block of the RTB to verify the continuity of the 125 Vdc contacts

in the manual switches,"~the 'block switch" must be held in the open position

when either switch is engaged.e -theK Ptr pnsi~it. If the "block switch" is

not held in the open position, it is not possible to independently verify the

continuity of the contacts since the "STAI contacts will close and provide a

parallel path to energize the shunt trip attachment.

On May 23, 1985, the NRC issued Generic Letter 85-09 which described the

appropriate methodology for verifying the operability of contacts in the

manual switches.

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

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

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train S Diagram

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DORS ASC/OEAB:DORS ADM:RPB SICB:DST

NFields* AGautam* JMain* SNewberry*

09/22/92 09/24/92 09/18/92 10/05/92 C/OEAB:DORS C/OGCB:DORS D/DORS

AChaffee GMar us o) / BGrimes

/ /92 f92 . / /92 DOCUMENT NAME: G:\ENF\INSTEXA.ENF

IN 92-XX

October xx, 1992 safety injection s ches deenergize the un ervoltage trip attachment and the

auto shunt trip relay. Deenergizing the to shunt trip relay causes the STA

contacts to close and a omatically ener ze the coil of the shunt trip

attachment.

When either manual SI or rea or trip switch is engaged, all respective

contacts in each switch change tat HSI, HS2, and SI represent contacts in

the manual reactor trip switches safety injection switches respectively.

Engaging either manual reactor tr or SI switches to the trip position

interrupts power to both the coi o the undervoltage trip attachment and to

the automatic shunt trip relay. If t "block switch" is not in an open

position during surveillance tsting o he switches, it is not possible to

verify the continuity of the witch (HS1, S2, SI) contacts since these

contacts are in parallel wI the STA cont ts.

On May 23, 1985, the NRC ssued Generic Lette 5-09 which described the

appropriate methodology for verifying the opera lity of contacts in the

manual switches.

This information n ice requires no specific action written response. If

you have any ques ons about the information in this n tice, please contact

one of the techn cal contacts listed below or the appro iate Office of

Nuclear Reactor egulation (NRR) project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Techni 1 contact: N. Fields, NRR

(301) 504-1173 Attachments:

1. Auto/Manual Reactor Trip Circuit Typical Train S Diagram

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OEAB:DOEA ASC/OEAB:DOEA ADM:RPB SI T, T

NFields* AGautam* JMain* SSWMberry&r>h

09/22/92 09/24/92 09/18/92 /92 Douts D0o5 PoS

C/OEAB:DOE C/OGCB:OGEA D/BGEA

AChaffee GMarcus 6Rossi- B6f66

/ /92 / /92 / /92 DOCUMENT NAME: G:\ENF\STEXAS.ENF

• SEE PREVIOUS CONCURRENCE

OEAB:DOEA ASC/OEAB:DOEA ADM:RPB SICB:DST

NFields* 'Aautam JMain* SNewberry

09/22/92 09/18/92 / /92 C/OEAB:DOEA C/OGCB:I D/DOEA

AChaffee GMarcus CRossi

/ /92 / /92 DOCUMENT NAME: G

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

you have any questions about the information in this notip# -ftlease contact

one of the technical contacts listed below or the appro iate Office of

Nuclear Reactor Regulation (NRR) project manager. /

Charles E. Ros

Or N iear Reactor Kegulation

Technical , N. Fields, NRR

(301) 504-1173 Attachment: L of Recently Isst NRC Information Notices

OEAB:DOE iF ASC/OEAB:DOEA ADM:RPB SICB:DST

Nfields AGautam A Jmain SNewberry

fi/tz192 / /92 /at/92 / /92 C/OEAB:DOEA C/OGCB:DOEA

Achaffee GMarcus

/ /92 / /92 l

DOCUMENT NAME: G:\ENF\STEXAS.ENF