Information Notice 1993-98, Motor Brakes on Valve Actuator Motors

Motor Brakes on Valve Actuator Motors

ML031060590
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:	12/20/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-098, NUDOCS 9312150064
Download: ML031060590 (8)

~'i Kv

K-

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 December 20, 1993 NRC INFORMATION NOTICE 93-98: MOTOR BRAKES ON VALVE ACTUATOR MOTORS

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 potential problems with the performance of

motor-operated valves (MOVs) resulting from improper operation of motor brakes

used on valve actuator motors. 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.

Background

Some MOVs have motor brakes installed to help minimize the inertial loads

during valve closure after the control switch has tripped. Motor brakes also

help prevent MOVs with non-locking gear mechanisms from inadvertently opening.

One type of motor brake is designed to be electromagnetically released and has

friction pads to slow the motor shaft following control switch trip. Improper

operation of motor brakes can result in problems with the performance of MOVs.

Description of Circumstances

In Maintenance Update 92-2, Limitorque Corporation informed the nuclear

industry that it had discovered, through operating experience and testing, that motor brakes do not substantially minimize the thrust load caused by

inertia when closing MOYs. Limitorque also stated that it did not qualify

motor brakes through its nuclear qualification testing. Limitorque warned

that voltage variation into the motor brake may render the brake inoperable.

Limitorque noted that disconnection of the brake leads does not render the

brakes inoperable and specified that the friction pads be removed. Each of

the following reports involve valves with Limitorque motor operators.

On August 4, 1993, the licensee of Crystal River Nuclear Plant, Unit 3, reported (Licensee Event Report 93-008) that seven MOVs with motor brakes

installed might receive insufficient voltage to allow the motor brakes to be

released under degraded voltage conditions. Of these seven MOVs, the licensee

9312150064 I o v't 3-o1S

PD9 Ie 19 3c) 0

IN 93-98 I-'December 20, 1993 declared a normally closed high-pressure injection suction NOV to be

inoperable on July 6, 1993. The licensee removed the friction disks and

electrical power connections from this NOV as well as from normally open

borated water storage tank suction NOV. The licensee tested another of the

seven MOVs to ensure that its motor brake would release under degraded voltage

conditions. The remaining four MOVs are locked in their safety function

position during plant operation.

On September 14, 1993, the licensee of Millstone Nuclear Power Station, Unit 2, notified NRC that it had declared four feedwater supply MOVs with

motor brakes installed inoperable when it determined that the MOVs might

receive insufficient voltage during degraded voltage conditions to allow the

motor brakes to release. The licensee relies on these MOVs as a backup for

feedwater isolation in the event of a main steam line break. The licensee

shut down Millstone Unit 2 in accordance with its plant technical

specification requirements. The licensee subsequently removed the motor

brakes.

On September 28, 1993, the licensee of James A. FitzPatrick Nuclear Power

Plant notified NRC of problems with the operation of motor brakes on two low- pressure coolant injection MOVs. The licensee determined that the motor

brakes were undersized to prevent the actuator spring pack from relaxing and

causing the torque switch to restart the actuator motor on a repeated basis.

Continuous restarting of the actuator motor can cause (1)damage to the motor

from overheating, and (2)excessive stress to the NOV by driving the valve

disk into its seat (sometimes referred to as a 'hammering" effect).

Discussiosn

In Generic Letter (GL) 89-10, 'Safety-Related Motor-Operated Valve Testing and

Surveillance," the NRC staff requested nuclear power plant licensees to

confirm the capability of safety-related MOVs to perform their intended

functions by reviewing NOV design bases, verifying NOV switch settings

initially and periodically, testing MOVs under design-basis conditions where

practicable, improving evaluations of NOV failures and necessary corrective

action, and trending NOV problems. In response to GL 89-10, licensees are

implementing programs to evaluate the design-basis capability of MOVs within

the scope of tbe generic letter.

As indicated by the discovery of NOV operability problems at Crystal River and

Millstone, some licensees may not be evaluating the minimum voltage required

to ensure the proper operation of motor brakes when determining the design- basis capability of MOVs with motor brakes installed. Improper operation of

motor brakes on MOVs could allow the motor to restart repeatedly as found at

FitzPatrick.

. I

K2IN 93-98 December 20 1993 Related Generic Communications

NRC has issued other information notices pertaining to MOVs. During the past

year, these have included NRC Information Notices 93-74, wHigh Temperatures

Reduce Limitorque AC Motor Operator Torque;" 93-54, "Motor-Operated Valve

Actuator Thrust Variations Measured With a Torque Thrust Cell and a Strain

Gage;" 93-01, 'Accuracy of Motor-Operated Valve Diagnostic Equipment

Manufactured by Liberty Technologies;" 92-83, 'Thrust Limits for Limitorque

Actuators and Potential Overstressing of Motor-Operated Valves;" and 92-70,

"Westinghouse Motor-Operated Valve Performance Data Supplied to Nuclear Power

Plant Licensees."

In addition, the hammering effect was specifically addressed in NRC

Information Notice 85-20, "Motor-Operated Valve Failures Due to Hammering

Effect," and its supplement.

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 orrthe appropriate Office of

Nuclear Reactor Regulation project manager.

Z24_-_O_ _

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: P. K. Eapen, RI

(215) 337-5150

Thomas G. Scarbrough, NRR

(301) 504-2794 Attachment:

List of Recently Issued NRC Information Notices

At&.dchment

IN 93-98 December 20, 1993 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

Failures of Yokes 12/17/93 All holders of OLs or CPs

Installed on Walworth for nuclear power reactors.

Gate and Globe Valves

93-96 Improper Reset Causes 12/14/93 All holders of OLs or CPs

Emergency Diesel for nuclear power reactors.

Generator Failures

93-95 Storm-Related Loss of 12/13/93 All holders of OLs or CPs

Offsite Power Events for nuclear power reactors

due to Salt Buildup located close to a large

on Switchyard Insulators body of salt water.

93-94 Unauthorized Forced 12/09/93 All holders of OLs or CPs

Entry into the Pro- for nuclear power reactors.

tected Area at Three

Mile Is-land Unit 1 on

February 7, 1993

93-93 Inadequate Control of 12/08/93 All holders of OLs or CPs

Reactor Coolant System for nuclear power reactors.

Conditions During Shutdown

Plant Improvements to 12/07/93 Al I holders of OLs or CPs

Mitigate Common Depend- for nuclear power reactors.

encies in Component

Cooling Water Systems

91-21, Inadequate Quality 12/07/93 All holders of OLs or CPs

Supp. 1 Assurance Program of for nuclear power reactors

Vendor Supplying and all recipients of

Safety-Related Equipment NUREG-0040, License Con- tractor and Vendor Inspec- tion Status Report" (White

Book).

89-77, Debris in Containment 12/03/93 All holders of OLs or CPs

Supp. 1 Emergency Sumps and for nuclear power reactors.

Incorrect Screen

Configurations

OL = Operating License

CP - Construction Permit

-

KJ~

IN 93-98 December 20, 1993 Related Generic Communications

NRC has issued other information notices pertaining to MO s. During the past

year, these have included NRC Information Notices 93-74, "High Temperatures

Reduce Limitorque AC Motor Operator Torque;" 93-54, "Motor-Operated Valve

Actuator Thrust Variations Measured With a Torque Thrust Cell and a Strain

Gage;" 93-01, "Accuracy of Motor-Operated Valve Diagnostic Equipment

Manufactured by Liberty Technologies;" 92-83, "Thrust Limits for Limitorque

Actuators and Potential Overstressing of Motor-Operated Valves;" and 92-70,

"Westinghouse Motor-Operated Valve Performance Data Supplied to Nuclear Power

Plant Licensees."

In addition, the hammering effect was specifically addressed in NRC

Information Notice 85-20, "Motor-Operated Valve Failures Due to Hammering

Effect," and its supplement.

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 project manager. Original signed by

Brian K.Grimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: P. K. Eapen, RI

(215) 337-5150

Thomas G. Scarbrough, NRR

(301) 504-2794 Attachment:

List of Recently Issued NRC Information Notices

• See nravinui concurrence naae

OFFICE *EMEB/DE/NRR *C:EMEB/DE/NRR *D:DE/NRR *OGCB/DORS/NRR

NAME TGScarbrough JANorberg JTWiggins RJKiessel/vsb

DATE 9/20/93 9/27/93 12/01/93 10/21/93 OFFICE *Tech Ed *EB/DRS/RI l*C:EB/DRS/RI *D:DRS/RI

NAME DGable PKEapen JPDurr WDHodges

DATE 10/22/93 1 i 11/29/93 11/29/93 OFFICE *C:OGCB/DORS/NRR

NAME GHMarcus I/

DATE 12/03/93 12(

Document Name: Y3-9U.IN

-

K>1 IN 93-xx

December 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 project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: P. K. Eapen, Region I

(215) 337-5150

Thomas G. Scarbrough, NRR

(301) 504-2794 Attachment: List of Recently Issued NRC Information Notices

C t4

• See nrevious concurrence naae 'd'0

OFFICE *EMEB/DE/NRR *C:EMEB/DE/NRR N *OGCB/DORS/NRR

NAME TGScarbrough JANorberg ~ T~igginsk RJKiessel/vsb

DATE 1 9/20/93 1 9/27/93 1tI!\ 93 10/21/93 OFFICE *Tech Ed *EB/DRS/RI *C:EB/DRS/RI *D:DRS/RI

NAME DGable PKEapen JPDurr WDHodges

DATE 10/22/93 111/29/93 , 1/29/93 11/29/93 OFFICE C:OGCB/DORS/NRR D: DORS/NRR

NAME GHMarcusmW BKGrines

I

DATE 1 f1/3 /93 _1_/ _/93 __ _p

Document Name: nrcin.3al

V

Effect," and its supplement.

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

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

AL. --- &- - IJ L L.1 - - &LL - -- - - l .- .... _ .A.

U11ne orIei ILecMicUa conMACU I ILsu D0OW or fne dppropridite urTice Ot

Nuclear Rea4:tor Regulatibn project manager.

Brian K. Grimes, Director

Division of Operating Reactor Supp t

Office of Nuclear Reactor Regula on

Technical ccontacts: P. K. Eapan, Region I

(215) 337-5150

Thomas G. Scarbrough, NRR

(301) 504-2794 Attachment: List of Recently Issued NRC Info ation Notices

Transmitted by JANorberg memorandum date September 27. 1993

• SPP nrpvioniis concurrence page

OFFICE *EMEB/DE/NRR *C:EMEBDE/NRR D:DE/NRR *OGCB/DORS/NRR

NAME TGScarbrough JAN berg JTWiggins RJKiessel/vsb

DATE 9/20/93 9//7/93 1i/ /93 10/21/93i

OFFICE *Tech Ed /EB/DRS/RI A C:EB/DRS/RI D:DRS/RI

NAME

DATE

OFFICE

T DGable

10/22/93 C:OGCB/MfRS/NRR

PKEapan

11 93

.0,>

D: DORS/NRR

'

JPDurr

IIg 93V

I Modge

11 V 93 NAME GHMarII BKGrimes

DATE II///93 11/ /93 Document Name: nrcln.3al

F

(215) 337-5240

Thomas G. Scarbrough, NRR

(301) 504-2794 Attachment: List of Recently Issued NRC Information Notices

Transmitted by JANorbera memorandum dated Sentomhbr 27. l 4 OB/DRS/RI C:OB/DRS/RI D:DRS/RI *EMEBID NRR *C:EMEB/DE/NRR

JSStewart LHBettenhausen M4WHodges TGS brough JANorberg

1O/ /93 IO/ /93 10/ /93 120/93 a 9/27/93 OGCB/DORS/NRR Tech Ed D:DE/NRR /C:OGCB/DORS/NRR D:DORS/NRR

RJKiesselftk , k JTW~ggins / GHMarcus BKGrimes

10 /93 10.ZZ/93 10/ /93 10/ /93 10/ /93 uoPcumenr name: nrcin.al /