Information Notice 1987-30, Cracking of Surge Ring Brackets in Large General Electric Company Electric Motors

Cracking of Surge Ring Brackets in Large General Electric Company Electric Motors

ML031130560
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	07/02/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-87-030, NUDOCS 8706250407
Download: ML031130560 (7)

p. .

SSINS No.: 6835 IN 87-30

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

July 2, 1987 NRC INFORMATION NOTICE NO. 87-30: CRACKING OF SURGE RING BRACKETS IN LARGE

GENERAL ELECTRIC COMPANY ELECTRIC MOTORS

Addressees

All nuclear power reactor facilities holding an operating license or a con- struction permit.

Purpose

This notice is provided to alert recipients to a potentially significant safety

problem that could result in the loss of safety-related equipment,' such as

residual heat removal (RHR), core spray, and high-pressure pumps that are

driven by large, vertical electric motors manufactured by General Electric

Company (GE). It is expected that recipients will review this information for

applicability and consider actions, as appropriate, to preclude a similar

problem at their facilities. However, suggestions contained'in this notice do

not constitute NRC requirements; therefore, no specific action or written

response is required.

Background:

Felt blocks are used in large electric motors to keep the windings separated

where they loop back at the end of the stator. The blocks are attached to a

surge ring that is held in place by L-shaped surge ring brackets welded to the

surge ring and bolted to the motor casing. Failure of-these surge ring brack- ets and cracking of the felt blocks allows movement and wear of the end-turns, leading to a reduction in insulation resistance and possible motor failure. In

addition, broken pieces of the surge ring bracket may enter the space between

the stator and the rotor, resulting in electrical or mechanical motor degrada- tion.

Description of Circumstances

During the 1985 outage at Peach Bottom Atomic Power Station, Unit 3, broken

surge ring brackets were discovered in a 2000-horsepower (hp) RHR pump motor

07/

TN 87-30

July 2, 1987 and a 600-hp core spray pump motor. Attempts to repair the brackets by welding

were unsuccessful, and they were removed from the motors at GE's suggestion.

The licensee' for Peach Bottom is reevaluating the motor design and the need to

replace the brackets.

During the week of November 10, 1986, the licensee for Cooper Nuclear Station

inspected Its 1000-hp RHR pump motors and discovered that three of four motors

had broken lower surge ring brackets and cracked upper and lower end-turn felt

blocks. In the B motor, five of six lower brackets were fractured. Repairs

were made and periodic visual inspections are being conducted.

GE informed the NRC on March 24, 1987 that the equipment affected in BWR plants

includes the RHR, core spray, and high-pressure core spray system electric

motors. GE recommended that annual inspections be performed until operating

experience indicates that this is no longer necessary. At plants where the

support brackets have been removed, GE stated that restoration actions should

be taken as soon as possible. Although GE notified BWR licensees of the Cooper

Station event, it did not notify PWR licensees. A list, which was provided to

the NRC by GE, of PWR facilities that have received large, vertical electric

motors from GE is attached. It should be noted that other'plants could have

similar motors.

Discussion:

The surge ring bracket, a 1-inch-wide by 1/8-inch-thick L-shaped piece of

carbon steel, has been breaking at the sharp bend. After the bracket breaks, a

1-inch-long portion remains attached to the surge ring by a double fillet weld.

If this weld fails, the 1-inch by 1-inch by 1/8-inch piece of steel may move

inside the motor. Although tests conducted at Cooper Station showed signifi- cant cyclic loading of the bracket when the motor was started, the bracket also

was shown to be subject to vibration during steady-state operation.

At Cooper Nuclear Station, surge ring brackets of an improved design, which

incorporated a larger bend radius, were installed and the motor Insulation

system was revarnished to fill and bond the cracks in the felt blocks. The

licensee is visually inspecting the brackets on a regular basis. This examina- tion is conducted without disassembling the pump motor, using either a

boroscope or a mirror inserted through the existing air vents. GE has recom- mended a complete disassembly and inspection at 10-year intervals to ensure the

continued qualification of these motors.

V .

IN 87-30

July 2, 1987 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.

Char es E ossi, Director

Division of OperationalEvents Assessment

Office of Nuclear Reactor Regulation

Paul Cortland, OSP

(301) 492-7190

Attachments:

1. List of PWR Facilities Known to Have Received

Large, Vertical Electric Motors from General Electric Company

2. List of Recently Issued NRC Information Notices

Attachment 1 IN 87-30

July 2, 1987 LIST OF PWR FACILITIES KNOWN TO HAVE RECEIVED LARGE,

VERTICAL ELECTRIC MOTORS FROM GENERAL ELECTRIC COMPANY

The plant numbers were not Identified for multi-unitsfacilities.

PLANT MOTOR SIZE IN HORSEPOWER

Arkansas Nuclear One 800

Bellefonte Nuclear Plant 900

Farley Nuclear Plant 600

Harris Nuclear Power Plant 1300

Indian Point Station 400

Millstone Nuclear Power Station 500, 600, 700

North Anna Power Station 400

Palo Verde Nuclear Station 600

Salem Nuclear Generating Station 1000

Seabrook Nuclear Station 600, 800

Sequoyah Nuclear Plant 700

SNUPPS 1750

St. Lucie Plant 500, 600

Turkey Point Plant 500

Vogtle Nuclear Plant 700

J 7- Attachment 2 IN 17-30

July P. 1987 LIST OF RECENT1.1 ' ISSUED

INFORMATION NOTIC:ES 1987

.nfn~tq.n

n-t. of-0

Iotice No. Sub~act_ Issuance Issued to

87-29 Recent Safet :y-Related 6/26/87 Incidents at t Large All NRK licensees

authorized to possess

Irradiators. and use sealed sources

in large irradiators.

87-28 Air Systems Problems at 6/22/87 All nuclear power

U.S. Light Water Reactors reactor facilities

holding an OL or CP.

87-27 Iranian Official Implie!. 6/10/87 All nuclear power

Vague Threat to U.S. reactor facilities

Resources holding an OL or CP,

research and nonpower

reactor facilities.

and fuel fabrication

and processing

facilities using or

possessinq formula

quantities of soecial

nuclear material.

87-26 Cracks In Stiffening Rings 6/11/87 on 48-Inch Diameter UF All uranium fuel

Cylinders. fabrication and

6 conversion facilities.

87-25 Potentially Significant 6/11/87 Problems Pesulting from All nuclear power

reactor facilities

Human Error Involving holding an AL or CP.

Wrong Unit, Wrong Train, or Wrong Component Events.

87-24 Operational Experience 6/4/87 Involving Losses of All nuclear power

Electrical Inverters. reactor facilities

holding an OL or CP.

87-23 Loss of Decay Heat Removal 5/27/87 During Low Reactor Coolant All PWRfacilities

tevlrOperatto- holding an OL or CP.

-

87-22 Operator Licensing Requali- S/22/87 All research and

fication Examinations aL nonpower reactor

Nonpower Reactors facilities.

OL

• Operating License

CP

• Construction Permit

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, D.C. 20555 FIRST CLASS MAIL

POSTAGE & FEES PAID

USNRC

WASH. D.C.

OFFICIAL BUSINESS PERMIT No. 047 PENALTY FOR PRIVATE USE. S300

I W

IN 87-30

July 2, 1987 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.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Paul Cortland, OSP

(301) 492-7190

Attachments:

1. List of PWR Facilities Known to Have Received

Large, Vertical Electric Motors from General Electric Company

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

• OSP *PPMB:ARM *AC/VIB:DRIS:NRR *C:OGCB:DOEA

PCortland TechEd EMerschoff CEBerlinger CERossi

6/25/87 6/25/87 6/25/87 6/25/87 6A87

IN 87-XX

June xx, 1987 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.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Paul Cortland, OSP

(301) 492-7190

Attachments:

1. List of PWR Facilities Known to Have Received

Large, Vertical Electric Motors from General Electric Company

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES (#6 C:OGCB:DOEA D: DOE~q

• OSP *PPMB:ARM *AC/VIB:DRIS:NRR

PCortland TechEd EMerschoff CEBerlinger CERossI

6/25/87 6/25/87 6/25/87 6/)087 6 M /87

.

IN 87-XX

June xx, 1987 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.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Paul Cortland, OSP

(301) 492-7190

Attachments:

1. List of PWR Facilities Known to Have Received

Large, Vertical Electric Motors from General Electric Company

2. List of Recently Issued NRC Information Notices

PPMB:ARMk,- C: OG94. UO-EA

D

PCorfl-aW' Te CEBerlinger CERossi

6/2 ,, /87 6/ciN /87 6/ars-/87 6/;Jr/87