ML20211N595

Part 21 Rept Re Cracked Limit Switch Rotors for Motor Operated Valves Supplied by Limitorque.Initially Reported on 860610.White (Melamine) Rotors Found Cracked Will Be Replaced W/Brown (Fibrite) Replacements

ML20211N595
Person / Time
Site:	Rancho Seco
Issue date:	06/10/1986
From:	Julie Ward SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
REF-PT21-86 JEW-86-102, NUDOCS 8607030160
Download: ML20211N595 (2)

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$SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street, P.O. Box 15830. Sacramento CA 95852-1830, (9)Q 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF C'AyFORNIA c ,, Q JEW 86-102 3 "M June 10, 1986 G $ k

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REGION V 0FFICE OF INSPECTION AND ENFORCEMENT U S NUCLEAR REGULATORY COMMISSION 1405 MARIA LANE SUITE 210 WALNUT CREEK CA 94596 ,

DOCKET N0. 50-312 LICENSE NO. DPR-54

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10 CFR 21 REPORT, CRACKING OF LIMITORQUE LIMIT SWITCH ROTORS In accordance with 10 CFR 21.21(b)(2), the Sacramento Municipal Utility District hereby submits a written report confirming the verbal notification to R. C. Sorensen on June 10,'1986, concerning cracked limit switch rotors for motor operated valves supplied by Limitorque Corp., Lynchburg, Virginia.

While performing routine inspections in accordance with the SMUD Environmental Qualification Monitoring Program, cracks were detected on the white molded limit switch rotors in the SMB series Limitorque Motor Operators. Two (2) rotors were found to have cracks out of approximately 10 motor operators inspected. The cracks are located at or near the groove pin which secures the molded plastic rotor to the metallic actuation shaft.

A nonconformance report was written on March 21, 1986 to address the hairline cracks observed in the rotors. Upon review by the Quality Assurance Department, an internal Occurrence Description Report was initiated on March 29, 1986, re-questing the Plant Review Committee (PRC) to evaluate the nonconformance for 10 CFR 21 reportability. After a preliminary investigation by Regulatory Com-pliance, the PRC, in a meeting held May 29, 1986, determined the observed hairline cracking constituted a defect in a basic component which is reportable, pursuant to 10 CFR 21, unless the NRC had been adequately notified. The Plant Review Committee requested an investigation to determine if the NRC had been adequately notified.

It should be noted that on June 2, 1986, a third cracked rotor was detected on another Class I motor operated valve.

On June 5, 1986, Limitorque Corp. was contacted to insure no previous 10CFR 21 l reports had been made on the cracked rotors. In a conversation with Dan Warsing and Bradley Stone, neither individual was aware of this cracking problem around the pin hole area of the rotor. Although Dan Warsing did indicate that the Union Electric Company, Callaway Nuclear Station, experienced cracking around the top of the rotor. Limitorque Corporation informed Westinghouse Electric Corp. of their findings of the cracked rotors at Callaway in a February 15, 1984 letter.

The NRC was also notified in a February 21, 1984 letter from Limitorque Corpora-tion (Attachment I), with no apparent response from the NRC to the industry.

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RANCHO SECO NUCLEAR GENERATING STATION O 14440 Twin Cities Road, Herald, CA 95638-9799;(209) 333-2935 1

.t s-l In a June 5, 1986 meeting, the PRC determined the Limitorque letter to the NRC did not adequately notify the NRC and that a 10 CFR 21 report was recommended.

! The three (3) cracked rotors are located in the motor operators of Class I valves SFV-22006, inlet to letdown coolers E-220B&C, SFV-66308, reactor building normal sump "B" discharge isolation, and HV-21517, pressurizer to pressurizer relief tank.

The defect identified by the PRC was a deviation in a basic component (i.e,

! Class I motor operators) in that the limit switch rotors have not performed ade-

quately for 40 years, which is a technical requirement of the procurement docu-ments.

The procurement documents did not appear to indicate that the rotors should be replaced during the 40 year life span. Currently, no limit switch rotors have failed, only cracks detected, but should a rotor fail due to the cracks, Control Room indication of valve position could be lost, the start capability of the motor could be lost, the torque bypass feature could be ic,st and any interlocks associated with the valve operator could be lost. Should any of the identified safety features valves not operate to their safety features position, a substan-tial safety hazard could exist in that there would be a loss of safety function (i.e., loss of redundant containment isolation capability) to the extent that there would be a major reduction in the degree of protection provided to the public health and safety. It should also be noted that generally, air operated valves are utilized in series with motor operated valves in providing containment isolation.

Recognizing that motor operated valves perform other safety related functions besides containment isolation, motor operator failures may have significant adverse effects on other safety related functions. Since only hairline cracks have been identified to date with no failures, the condition at Rancho Seco does not currently meet the 10 CFR 50.73 reporting criteria.

The Rancho Seco Nuclear Maintenance Division is increasing the inspection of the motor operators from the environmental qualification program required 10%

per refueling outage, to a 100% inspection of all Class I motor operators. Any white (melamine) rotors found cracked will be replaced with the brown (fibrite) replacements currently being supplied by Limitorque Corporation. The inspection and replacement will be completed prior to startup.

The District considers Limitorque Corporation to be better qualified to provide

! to the NRC an itemization of those facilities which may be affected by this defect.

If there are any questions, please contact Ron W. Colombo at Rancho Seco Nuclear l Generatin Station Unit No. 1.

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. WARD ASSISTANT GENERAL MANAGER, NUCLEAR (ACTING) cc: NRR I

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February 21,1934 Office of the Director .

iluclear Regulatory Commission Inspection & Enforcement Washington DC 2E

Subject:

Limitorque Advisory Gentlemen:

A recent experience at the Union Electric Company, Callaway tiuclear Station, has prompted an evaluation by our Design Review Committee.

It was judged that, although a design deficiency is not involved, the possi-bility of similar situations arising in the nuclear industry would suggest a 10CFR (Part 21) advisory might be appropriate from the standpoint of mainte-nance and on-going equipment inspection by the various utilities.

We enclose a copy of our letter February 15,1984, to the Westinghouse Electric Corporation which contains full detail on this situation along with our evalu-ation and recomendations.

Yours very truly, LIMITORQUE CORPORATIO?l F. K. Denham Executive Vice President FK0:dr enc.

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1 LIMlTORQ'UE . CORPORATION L > j 39E k 5114 Woodait Road . P. O. Box 11318

• Lynchburg, Virginia 24506 Telephone-804 528 4400 lb i

E N Telex--82-9448

. February 15, 1984 Westinghouse Electric Corporation Electro Mechanical Division Cheswick Avenue Cheswick, PA 15024 Attention: Mr. Rudy Mrozoski Gentlemen: ..

Subject:

Limitorque Limit Switch 'R'otors over the past three years we have had sporadic reports of In each case, we requested that samples be returned to analysis.

were surface cracks resulting from post mold shrinkage, c nature and having no effect on the integrity of the part.

callaway Station, of white limit switch rotors havingTwocracks. ,

samples were returned to us from the callaway site.

were subjected formance withtothe a material materialanalysis and also found to be in con-The components specifications.

nitely had a greater depth than the surface cracks which we haveThese cra investigated the component.previously and could possibly effect the integr it y of that it required several sharp blows to break the melding Although the limit switch rotor is not a load bearing component, piping .

vibration or normal in-service shock might possibly cause a similar significantly cracked rotor to break and impair its ability to function.

It should be noted that the more severe cracks observed shipment and installation.in the Calloway samples may have resulted moldingsIn summary, that these are the first cracked white limit suitch The extent of thesewe have cracksexamined cannot be which cannot be determined classified by a as cosmeti visual examinatio n, consequently, the component must be destroyed to determine the crack  !

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[rMITOROUE CORPORATION Sheet Na.

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2 Westinghouse Electric Corn.

Mr. Rudy Mrozoski February 15, 1984 depth.

It is our recommendation that any white limit switch

'- components which are found with cracks should be replaced as we are unaware of any non-destructive procedure that would differen-tiate between a harmless shrinkage crack and a crack that could impair operation.

madeOurof acurrent standard rotor for inside containment service is brown material. In 1979, the white material was replaced by the brown compound because the white material was no longer available from the supplier. The brown rotors are directly inter-changeable with the white components and there have not been any reports of cracking in the brown material.

Replacement parts of'the current design (brown color material) can be purchased from Limitorque Corporation.

Very truly yours, LIMITORQUE CORPORATION b)d 6td Daniel S. Warning Technical Managor

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Q 4 529 4400 LIMITCPOUE CCRP L. JS 86 15:58 005 PROCEDURE FOR REPLACING ROTOR ON LIMITORQUES LIMIT SWITCH

1. Remove the damaged rotor.

2. Place the new rotor (49) on the stem spur pinion shaf t (47), aligning the hole molded in the rotor with the I hole already drilled in the shaf t. I

3. Using a no. 40 drill, and the existing hole in the shaft as a guide, drill thru the rotor.

4. Install the 3/32 inch diameter x 3/4 inch long groove pin (50).

LIMITORQUE CORPORATION t

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