Information Notice 1993-78, Inoperable Safety Systems at a Non-Power Reactor

Inoperable Safety Systems at a Non-Power Reactor

ML031070080
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	10/04/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-078, NUDOCS 9309290007
Download: ML031070080 (9)

S

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 4, 1993 NRC INFORMATION NOTICE 93-78: INOPERABLE SAFETY SYSTEMS AT A NON-POWER

REACTOR

Addressees

All holders of operating licenses or construction permits for test and

research reactors.

Purpose

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

notice to alert addressees to a problem which resulted in inoperable safety

systems at a non-power reactor. 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 April 28, 1993, after a number of spurious scrams had occurred, the

licensee for the University of Virginia Research Reactor shut down the reactor

and began troubleshooting activities to determine the cause of the problem.

The reactor had been experiencing spurious scrams for some time and the

licensee had concluded that the scrams were not caused by'electrical

transients or line noise. The licensee suspected the reactor-scram logic to

be the cause of the scrams. The reactor scram logic consists of two trains

that cause power to different magnets to be cut off on receiptIof a scram

signal. This in turn releases control rods and shuts down the'reactor. While

investigating the problem, the senior reactor operator (SRO) interchanged

components of the scram logic system between the two trains. Among these

components were solid-state relays and mixer-drivers (M/Ds) which act as a.

28-channel "OR" gate in the scram logic. After consulting the facility safety

analysis report and visually inspecting the exterior of the components, the

SRO assumed that the interchanged components were identical. However, the

M/Ds had been internally modified in the 1970s to tie unused inputs together

and were no longer identical.

After the M/Ds had been exchanged and no spurious scram signals were received

for 30 minutes, the reactor administrator and the SRO started the reactor.

Neither the reactor administrator nor the SRO recognized that the

troubleshooting activities-were actually a maintenance or modification

function and that testing to verify the operability of the reactor scram

system was required before the reactor was restarted.

9309290007 R No.'De, qs o7r 73l

IN 93-78 October 4, 1993 After operating for approximately 5k hours, the reactor was shut down by

driving the rods into the core. With three of the four control rods seated, licensee personnel then introduced a scram signal into the reactor

electronics using the intermediate range channel switch. However, the

electronics did not generate a scram signal as expected. The licensee

investigated and found that the M/Ds were not internally identical as

described above. Further investigation showed that the following scram

signals were inoperable: the two power level scrams, intermediate range

period scram, primary coolant low flow scram, loss of power to the primary

pump scram, intermediate channel range switch scram, and key switch scram.

The licensee returned the M/Ds to their original positions and tested the

reactor to ensure that the reactor electronics had not been damaged.

To prevent a recurrence of this problem, the licensee made the following

changes: (1) revised the facility standard operating procedures (SOPs) to

clearly define maintenance and troubleshooting activities, (2) added a

checklist to the SOPs to specifically control maintenance activities, and

(3) added a checklist to the SOPs to verify the operability of the reactor

safety systems after an unplanned reactor scram. Other changes were also made

to the SOPs to ensure management control over maintenance.

The licensee checked the reactor electronics against the schematics and found

that changes had been made to console modules that were not reflected in the

schematics. The licensee found two instances where externally identical

components were internally different and therefore not interchangeable. After

completing this check, the licensee labeled the modules that had been modified

to clearly indicate that they were unique and not interchangeable.

Discussion

The circumstances described above demonstrate the importance of recognizing

and controlling maintenance and modification actions. Clearly defining

maintenance activities in facility procedures and providing training to

personnel can be effective methods for controlling such activities. Also

important to reactor safety is updating schematics of reactor electronics to

reflect modifications to safety systems. Performing testing of the affected

safety systems after activities of the type described above may prevent the

occurrence of similar events.

IN 93-78 October 4, 1993 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.

orig /s/'d by AEChaffee/for

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: A. Adams, Jr., NRR

(301) 504-1127 C. Bassett, RII

(404) 331-5570

Attachment:

List of Recently Issued NRC Information Notices

• See previous concurrence

ONDD:LA* ONDD:PM* RII* TECH ED.* C/ONDD* C/OGCB* D aI

EHylton AAdams:dmj CBassett MMejac SWeiss GHMarcus BGrimes

7/30/93 7/30/93 8/03/93 7/29/93 8/03/93 9/07/93 9kM/93 OGCB:DORS*

JBirmingham

9/07/93 OFFICIAL RECORD COPY

DOCUMENT NAME: 93-78.IN

j

IN 93- September , 1993 Page 3 of

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 Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: A. Adams, Jr., NRR

(301) 504-1127 C. Bassett, RII

(404) 331-5570

Attachment:

List of Recently Issued NRC Information Notices

• See previous concurrence

ONDD:LA* ONDD:PM* RII* TECH ED.* C/ONDD* C/OGCB*

EHylton AAdams:dmj CBassett MMejac SWeiss GHMarcus BGrimes~I(

7/30/93 7/30/93 8/03/93 7/29/93 8/03/93 9/07/93 9X /93'

OGCB:DORS*

JBirmingham

9/07/93

OFFICIAL RECORD COPY

DOCUMENT NAME: MNTNCIN.JLB

IN 93-xx

September 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

one of the technical contacts 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 contacts: A. Adams, Jr, NRR C. Bassett, RII

(301) 504-1127 (404) 331-5570

Attachment:

List of Recently Issued NRC Information Notices

• See previous concurrence

ONDD:LA* ONDD:PM* RII* TECH ED.* C/ONDD C/OGe D/DORS

EHylton AAdams:dmj CBassett KMejac SWeiss GHMa9 s BGrimes

7/30/93 7/30/93 8/03/93 7/29/93 8/03/93 9/ ? /93 9l /93 OGCB:DORS

JBirminghgm

9/7/9 P zwc

OFFICIAL RECORD COPY

DOCUMENT NAME: MNTNCIN.JLB

K

s~IN 93- (Date) problem was corrected by returning the M/Ds to their original position. The

reactor was tested to ensure that the reactor electronics had not been

damaged.

The UVRR staff has instituted a number of corrective actions to prevent a

recurrence of this problem. Facility standard operating procedures (SOPs)

have been revised to clearly define maintenance and troubleshooting, a new

checklist to control maintenance has been developed and added to the SOPs, a

new checklist to be followed after an unplanned reactor scram to verify

operability of the reactor safety systems has been added to the SOPs, and

other changes have been made to the SOPs to increase management control over

maintenance. The reactor electronics have been checked against schematics, and the schematics have been updated when necessary. The licensee found that

various changes had been made to console modules that were not reflected in

the schematics. The reactor console was checked for other externally

identical components that were internally different and not interchangeable.

Two instances of this type were identified. Modules in the console were

clearly labeled to indicate if any modifications were made and if they were

unique and not interchangeable. A sign was added to the reactor console

reminding operators that modules in the console were not interchangeable.

Discussion

This problem emphasizes the importance of recognizing and controlling

maintenance functions at NPRs. What constitutes maintenance should be clearly

defined in the facility procedures and understood by the staff. The

operability of safety systems should be verified every time maintenance is

performed on a system.

Also important is having clear, up-to-date schematics of reactor electronics

and procedures that ensure that they will be consulted during maintenance.

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 Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: A. Adams, Jr.

(301) 504-1127 C. Bassett

(404) 331-5570

DISTRIBUTION:

Attachment: Central File GMarcus

List of Recently Issued NRC Information Notices BGrimes AAdams

SWeiss EHylton

• See pevious concurrences CBasse

O pLJt-' ONDD:P%, RTf TECH ED.* OGCB:BC DORS:DD

E on AAdaM4>i CBasrett MMejac GMarcus 3flss BGrimes

6/8/93/ 93 7/29/93 / /93 Q /x/93 / /93 OFFICIAL RECORD COPY p" & )

DOCUMENT NAME: A:IN2.AA (ONDD DOCUMENTS DISK)

i.-2 IN 93- (Date) pump scram, intermediate channel range switch scram and key switch scram were

found to Oe inoperable. This problem was corrected by returning the M/Ds to

their orininal position. The reactor was tested to ensure that no damage

occurred to the reactor electronics.

The UVRR staff Was instituted a number of corrective actions to prevent

reoccurrence of is problem. Facility Standard Operating Procedures (SOPs)

have been revised o clearly define maintenance and troubleshooting, a new

checklist to contro maintenance has been developed and added to the SOPs, a

new checklist to be llowed after an unplanned reactor scram to verify

operability of the rea tor safety systems has been added to the SOPs, and

other changes have been ade to the SOPs to increase management control over

maintenance. The reacto electronics have been checked against schematics and

schematics updated when ne essary. The licensee found that various changes

had been made to console mo les that were not reflected in the schematics.

The reactor console was revie ed for other externally identical components

that were internally different nd not interchangeable. Two instances of this

type were identified. Modules the console were clearly labeled to indicate

if any modifications were made an if they were unique and not

interchangeable. A sign was added o the reactor console reminding operators

that modules in the console were not nterchangeable.

Discussion

This problem emphasizes the importance o ecognizing and controlling

maintenance functions at NPRs. What const utes maintenance should be clearly

defined in the facility procedures and unde tood by the staff. The

operability of safety systems should be veri ed every time that maintenance

is performed on a system.

Also important is having clear, up-to-date schema ics of reactor electronics

and procedures that ensure that they will be consu ted during maintenance.

This information notice requires no specific action written response. If

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

the technical contact listed below or the appropriate fice of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Directo

Division of Operating Rea tor Support

Office of Nuclear Reactor gulation

Technical contacts: A. Adams, Jr. DISTRIBUTION:

(301) 504-1127 Central File GMarcus

C. Bassett BGrimes AAdams

(404) 331-5570 SWeiss ylton

Attachment:

List of Recently Issued NRC Information Notices

ONDD:LA ONDD:PM TECH ED. OGCB:BC ONDD:D DORS:DD

EHylton AAdams:dmJ fl t GMarcus SWeiss BGrimes

/ /93 / /93 ' /aj/93 / /93 1 /93 / /93

OFFICIAL RECORD COPY

DOCUMENT NAME: A:IN2.AA (ONDD DOCUMENTS DISK)

KJ

IN 93-78 October 4, 1993 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 Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: A. Adams, Jr., NRR

(301) 504-1127 C. Bassett, RII

(404) 331-5570

Attachment:

List of Recently Issued NRC Information Notices

N- AttachJ

IN 93-7r

October 4, 1993 Page I of I

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

93-77 Human Errors that Result 10/04/93 All nuclear fuel cycle

in Inadvertent Transfers licensees.

of Special Nuclear

Material at Fuel Cycle

Facilities

93-76 Inadequate Control of 09/21/93 All holders of OLs or CPs

Paint and Cleaners for for nuclear power reactors.

Safety-Related Equipment

93-75 Spurious Tripping of 09/17/93 All holders of OLs or CPs

Low-Voltage Power Circuit for nuclear power reactors.

Breakers with GE RMS-9 Digital Trip Units

93-74 High Temperatures Reduce 09/16/93 All holders of OLs or CPs

Limitorque AC Motor for nuclear power reactors.

Operator Torque

93-73 Criminal Prosecution of 09/15/93 All NRClicensees.

Nuclear Suppliers for

Wrongdoing

93-72 Observations from Recent 09/14/93 All holders of OLs or CPs

Shutdown Risk and Outage for nuclear power reactors.

Management Pilot Team

Inspections

93-71 Fire at Chernobyl Unit.2 09/13/93 All holders of OLs or CPs

for nuclear power reactors.

93-70 Degradation of Boraflex 09/10/93 All holders of OLs or CPs

Neutron Absorber Coupons for nuclear power reactors.

93-69 Radiography Events at 09/02/93 All holders of OLs or CPs

Operating Power Reactors for nuclear power reactors

and all radiography

licensees.

OL - Operating License

CP

• Construction Permit

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