Information Notice 1987-05, Miswiring in a Westinghouse Rod Control System

Miswiring in a Westinghouse Rod Control System

ML031130635
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, 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:	02/02/1987
From:	Jordan E NRC/IE
To:
References
IN-87-005, NUDOCS 8701220053
Download: ML031130635 (4)

SSINS NO.: 6835 IN 87-05 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 February 2, 1987 IE INFORMATION NO. 87-05: MISWIRING IN A WESTINGHOUSE ROD CONTROL SYSTEM

Addressees

All Westinghouse nuclear power reactor facilities holding an operating license

or a construction permit.

Purpose

This notice is to alert addressees to the miswiring of circuit card inter- connections in the Westinghouse-supplied rod control system of a Westinghouse

reactor. It is suggested that recipients review the information for applic- ability to their facilities and consider actions, if appropriate, to preclude

similar problems occurring 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

Beaver Valley Unit 1

On December 1, 1986, with the plant at full power, the bank selector switch in

manual, and all rods fully withdrawn, the operator inserted control rods

consistent with a minor power reduction. Although control bank 'D' rods were

expected to move, the operator observed that control bank 'A' rods inserted

two steps.

Subsequent investigation revealed that two circuit boards in the bank overlap

unit (BOU) of the rod control system had been wired together improperly. This

miswiring was determined to have existed since initial installation of the rod

control system when the plant was new. Rod control systems of this design have

been supplied for approximately 60 other Westinghouse nuclear units.

Discussion:

With the rod control system in manual or automatic, the BOU automatically

selects the sequence and overlap of the control banks. To keep track of the

process, each in or out step of the control banks is recorded by a counter in

the BOU. The BOU count increases from 000 to 999 as control bank rods are

stepped out. Shutdown bank motion does not affect BOU count. To support

special evolutions such as troubleshooting and repair, the BOU is fitted with

"+1", "-1" and "reset" push buttons which permit advancing, retarding, or

zeroing, respectively, the BOU count. Depressing any of these buttons does not

3~O03

IN 87-

1987 Page 2 of 2 automatic, any demand for rod motion would result in movement of bank 'A' rods, as was observed in this case. Placing the plant in a potentially significant

unanalyzed condition might therefore result from this problem, especially if

the rod control system were in automatic and plant conditions demanded

significant rod motion.

After testing eliminated the possibility of a failed BOU electronics card, it

was concluded that the BOU counter had been zeroed by unauthorized operation of

the BOU +1 button. In a properly wired BOU, depressing the +1 and -1 buttons

an equal number of times would have no net effect on BOU count, i.e., the

final count would be the same as it had been prior to button manipulation.

In the miswired configuration, the BOU count used to supervise rod motion was

reduced to 000. It is important to note, however, that the BOU count displayed

at the push button station was not affected by the miswiring, and responded

properly to use of the +1 and -1 buttons. In addition, had the unit

experienced a scram with BOU count out of alignment, this problem would have

gone undetected, since BOU count automatically resets to 000 when a scram is

received.

This problem was rectified at Beaver Valley Unit 1 by rewiring the BOU circuit

board interconnections in the correct configuration. The unit remained at

power during repairs. The Beaver Valley Unit 2 rod control system was

inspected and found not to be affected.

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.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Kevin Wolley, IE

(301) 492-9428 Attachment: List of Recently Issued IE Information Notices

• SEE PREVIOUS CONCURRENCES Z

• DEPER:IE *DEPER:IE DEPER;LE $ER:IE ER:IE

• DEPER:IEAL

KWolley GLanik DGab V' JRosenthal RBaer / SSchwartz ELid

12/24/86 12/29/86 01/6 /87 0 g /87 12/30/86 01//b/ ., 017 tY87

Attachment 1 IN 87-05 February 2, 1987 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

87-04 Diesel Generator Fails 1/16/87 All power reactor

Test Because of Degraded facilities holding

Fuel an OL or CP

87-03 Segregation of Hazardous 1/15/87 All NRC licensees

87-02 Inadequate Seismic Quali- 1/15/87 All power reactor

fication of Diaphragm facilities holding

Valves by Mathematical an OL or CP

Modeling and Analysis

87-01 RHR Valve Misalignment 1/6/87 All PWR facilities

Causes Degradation of holding an OL or CP

ECCS in PWRs86-110 Anomalous Behavior of 12/31/86 All BWR facilities

Recirculation Loop Flow holding an OL or CP

in Jet Pump BWR Plants86-109 Diaphragm Failure In Scram 12/29/86 All BWR facilities

Outlet Valve Causing Rod holding an OL or CP

Insertion

86-108 Degradation Of Reactor 12/29/86 All PWR facilities

Coolant System Pressure holding an OL or CP

Boundary Resulting From

Boric Acid Corrosion

86-107 Entry Into PWR Cavity With 12/29/86 All power reactor

Retractable Incore Detector facilities holding

Thimbles Withdrawn an OL or CP

86-106 Feedwater Line Break 12/16/86 All power reactor

facilities holding

an OL or CP

86-105 Potential For Loss Of 12/19/86 All holders of OL or CP

Reactor Trip Capability for PWR or BWR

At Intermediate Power

Levels

OL = Operating License

CP = Construction Permit

I I

IN 86-

1986 in movement of bank 'A'rods, as was observed in this case. Placing the plant

in a potentially significant unanalyzed condition might therefore result from

this problem, especially if the rod control system were in automatic and plant

conditions demanded significant rod motion.

After testing eliminated the possibility of a failed BOU electronics card, it

was concluded that the BOU counter had been zeroed by unauthorized operation of

the BOU +1 button. In a properly wired BOU, depressing the +1 and -1 buttons

an equal number of times would have no net effect on BOU count, i.e., the

final count would be the same as it had been prior to button manipulation.

In the miswired configuration, the BOU count used to supervise rod motion was

reduced to 000. It is important to note, however, that the BOU count displayed

at the push button station was not affected by the miswiring, and responded

properly to use of the +1 and -1 buttons. In addition, had the unit

experienced a scram with BOU count out of alignment, this problem would have

gone undetected, since BOU count automatically resets to 000 when a scram is

received.

This problem was rectified at Beaver Valley Unit 1 by rewiring the BOU circuit

board interconnections in the correct configuration. The unit remained at

power during repairs. The Beaver Valley Unit 2 rod control system was

inspected and found not to be affected.

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.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Kevin Wolley, IE

(301) 492-9428 Attachment: List of Recently Issued IE Information Notices

Da :IE D A DEPER:IE DEPER:IE DRX:IE DD:DEPER:IE D:DEPER:IE

KWolley B41 DGable JRosenthal RBaer SSchwartz ELJordan

12/g(/86 A2M /86 12/ /86 12/ /86 12/3(/86 12/ /86 12/ /86