ML19326D950
| ML19326D950 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 07/03/1980 |
| From: | Robert Carlson NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 8007250287 | |
| Download: ML19326D950 (1) | |
Text
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o UNITED STATES
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]3 NUCLEAR REGULATORY COMMISSION 3
j REGION 1 0,
631 PARK AVENUE
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KING OF PRUSSIA, PENNSYLVANIA 19406 Docket No. 50-352 JUL 0 3 LW 50-353 Philadelphia Electric Company WITN: Mr. John S. Kemper Vice President 1
Engineering and Research 2301 Market St.
j Philadelphia, Pennsylvania 19101 Gentlemen:
Subject:
4KV Switchgear Circuit Breaker Auxiliary Switch Crank Assembly Defect (Your letter SDP. #11 of June 20,1980)
Thank you for your letter, referenced above, which forwarded a final report pursuant to 10 CFR 50.55(e) regarding the subject matter.
Your report will be reviewed and evaluated, and should we require additional infonnation concerning this matter, we will contact you.
Your cooperation with us is appreciated.
Sincerely,
'7geh$.
~
Robe t T. Ca on, Chief Reactor Construction and Engineering Support Branch cc:
V. S. Boyer, Senior Vice President, Nuclear Power 8007250 M S
PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 JOHN S. KEMPER v sCE+n ssID ENT 19, 3 ; a g,.g g,
o.....................
Mr. Boyce Grier, Director Office of Inspection and Enforcement Commission United States Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406
Subject:
Significant Deficiency Report No. 11 4KV Switchgear Circuit Breaker Auxiliary Switch Crank Assembly Defect
Reference:
Telecon of May 22, 1980 H.
R. Walters (PECO) to R.
McGaughy (NRC)
File:
QUAL 2-10-2 (SDR #11')
Dear Mr. Grier:
Attached is our final report on the above subj ect deficiency which was reported to th,e USNRC per the referenced telacon in accordance with 10CFR50.55 (e).
If there cre any questions on the natter we would be pleased to discuss them with you.
Sincerely, 60 [ /XL,!~-
i RJL/gra Attachment Copy to:
Director of Inspection and Enforcement l
United States Nuclear Regulatory Commission l
Washington, D.C.
20555 dupe of M b 2 7 0 2 2 4-
i 1
FINAL REPORT ON 4 kV SWITCHGEAR CIRCUIT BREAKER AUXILIARY SWITCH CRANK ASSEMBLY DEFECT AT LIMERICK GENERATING STATION UNITS 1 AND 2 4
l Philadelphia Electric Cc:::pany June 1980 SDR-ll-1
^
TABLE OF CONTE 7fS
1.0 INTRODUCTION
2.0 DESCRIFTION OF PROELDi 3.0 ANALYSIS OF SAFETI HELICATIONS 4.0 CORRECTIVE ACTION "dKEN
5.0 CONCLUSION
S O
SDR-11-2
l.0 INTRODUCTION The Limerick Generating Station uses 4 kV metal-clad switchgear as safeguard switchgear in safety related systems.
A manufacturing deficiency in the crank assemblies that operate the compartment-mounted, cirettit breaker auxiliary switches has been identified.
It has been determined that plant safety could have been compromised had these manufacturing deficiencies gone unidentified.
In compliance with 10CFR50.55(e), this Tinal Report is issued to describe the deficiency, analyze the safety implication of the deficiency, and describe the action taken to correct the deficiency.
This significant deficiency was reported via telecon to the USNRC, Region 1 on May 22,1980.
2.0 Description of Problem A defective circuit breaker auxiliary switch linkage on ITE Type 5HK350, Stored-Energy Metal-Clad Switchgear has been discovered by the Limerick Generating Station Bechtel QC personnel.
Following the discovery of a 10/32 nut on the floor of a switchgear compartment, an inspection determined that the captive nut had fallen off the stud that holds the operating link to the auxiliary switch crank.
The nut loosened because the brass lock washer in the assembly had flattened when the nut was tightened and did not provide sufficient opposing torque to secure the nut.
Further inspec cion found some assemblies in other compartments in which the locking nut on a similar stud was loose.
In some cases, locking nuts were loosened by simulating breaker opefation by manually operating the link.
There are a total of 72 circuit breaker compartments in the eight 4 kV safeguard switchgear line-ups; each nuclear unit has four 4 kV safeguard buses equipped with 8 to 10 circuit breaker compartments each.
Each compartment has either 2 or 3 auxiliary switches ganged together.
All compartments have been placed in their final location.
3.0 Analysis of Safety Implications An auxiliary switch or group of auxiliary switches that is not operated by the closing or opening of the circuit breaker because the operating link has become disconnected from the auxiliary switch crank will not initiate the proper control action since the auxiliary switch contacts are used in interlocking controls of equipment regnired to operate during an accident condition.
Failure of the auxiliary switches to operate could result in impairment of the scoper operation of safety related equipment in the event of an accidsnt requiring safe shutdoso.
SDR-11-3
4.0 Carr:ctiva Acti n Tak2n A representative of the ITE Switchgear Division of Gould-Brown Boveri has visited the Limerick site and inspected a representative number of the switchgear compartments.
The manufacturer has determined that the brass internal lock washers are an improper application. The brass lock washer flattens when tightened and does not adequately restrain the nut from loosening when the linkage is operated.
A 100% inspection of the subject switchgear will be made and the nuts will be secured on the studs in a manner that will prevent them from loosening during operation.
It is anticipated that all corrective actions will be completed by December 31, 1980.
5.0 Conclusions It is concluded that the corrective action described above will correct and preclude recurrence of the defects in the ITE Type 5HK350, metal clad switchgear auxiliary switch assembly at Limerick Generating Station.
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SDR-ll-4 j