ML19276E841
| ML19276E841 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon, Cook, Humboldt Bay |
| Issue date: | 03/16/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7903210405 | |
| Download: ML19276E841 (1) | |
Text
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UNITED STATES 0
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1990 N. C ALIFOHNI A 00VLEVARD 9
9 W ALNUT C RE EK. C ALIFOR NI A 94536 March 16,1979 Docket flos. 50-133 50-275 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: Mr. Philip A. Crane, Jr.
Assistant General Counsel Gentlemen:
The enclosed IE Circular I;o. 79-04, is forwarded to you for information.
If there are any questions related to your understanding of the suggested actions, please contact this office.
Sincerely,
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Director
Enclosures:
1.
IE Circular No. 79-04 2.
List of IE Circulars Issued in 1979 cc w/encls:
W. Barr, PG&E W. A. Raymond, PG&E R. Ramsey, PG&E E. Weeks, PG&E, Humboldt Bay J. D. Worthington, PG&E 790321do5
IE Circular No. 79-04 f-farch 16, 1979 LISTI!G OF IE CIRCULARS ISSUED IN LAST TWELVE ft0HTHS Circular Subj ect Date of Issued To No.
Issle 78-16 Limitorque Valve 7/26/78 All Holders of Actuators Reactor OLs or cps 78-17 Inadequate Guard Training /
10/13/78 All Holders of Qualification and Falsified and applicants Training Records for Reactor OLs.
78-18 UL Fire Test 11/6/78 All Holders of Reactor OLs or cps 78-19 fianual Override (Bypass) 12/28/78 All Holders of of Safety Actuation Signals cps 79-01 Administration of 1/12/79 All Medical Unauthorized Byproduct Licensees except Material to Humans Teletherapy Medical Licensees and each Radiopharmaceutical Suppliers 79-02 Failure of 120 Volt Vital 2/16/79 All Holders of AC Power Supplies Reactor OLs and cps 79-03 Inadequate Guard Training-2/23/79 All Holders of Qualification and Falsified and applicar.ts Training Records for Special fluclear Material Licenses in Safeguards Group I 79-04 Loose Locking Nut on 3/16/79 All Holders of Limitorque Valve Operators Reactor OLs or cps Enclosure Page 1 of 1
IE Circular t!o. 79-04 ftarch 16, 1979 Page 2 of 2 Pennsylvania Power and Light Company (PP&L) infomed the i;RC that the generic problem of failure te stake locking nuts exists with Limitorque Type SMC valve operators and Type SMB operators.
PP&L Co. was advised of the problem by Bechtel Corporation. The information was submitted to the f;RC on March 2, 1979 as a deficiency at the Susquehanna Steam Electric Station. The Type StiC Instruction and Maintenance Manual SMCI-04-78 and Drawing No. 21-497-0013-3 provide directions for securing the locking nut.
All holders of construction permits and operating licenses should be aware that the potential for valve operator failure exists if the locking nut is not adequately se;ured. The recommended action is to survey all installed Limitorque Operator Types SMB-000 through SMB-5 and Type SftC to detemine that the locking nut is secure and to verify that assembly and maintenance instructions contain directions for securing the locking nut either by staking, per the vendor's reccmmendation, or another acceptable manner.
No written response to this Circular is required.
If you require additicnal information regarding this subject, contact the Director of the e ropriate fiRC Regional Office.
IE Circular No. 79-04 March 16,1979 Page 1 of 2 LOOSE LOCKIftG NUT ON LIl4ITORQUE VALVE OPERATORS Description of Circumstances:
On December 8,1978, Fort Calhoun Station Unit flo. I reported that 30 out of 65 Lim; torque Type SMB valve operators did not have the locking nut fastened securely in accordance with the manufacturer's recommendation.
If this locking nut is not secure it can loosen and allow the stem nut to move axially to the point that the splines are disengaged; resulting in a loss of drive to the valve stem.
The ! :ensee reported that several locking nuts were slightly loose but in no instance had the stem nut backed out enough to affect the operation of the valve.
This licensee was made aware of the potential problen by a letter of July 28,1978, from the NSSS supplier, Combustion Engineering, Inc.
Other plants have reported similar findings.
On April 27, 1977, Davis-Besse Nuclear Power Station Unit No.1, reported that two valve operability failures had been caused by locking nuts loosening and falling off. During the ensuing inspection program a total of 65 out of 144 safety related valve operators required staking. Arkansas fluclear One (ANO), Unit 2, reported on June 29, 1978, that several valve operators required staking. A subsequent inspection at ANO Unit 2 was made by an IE inspector who identified records that 15 out of 17 SMB operators provided by the fiSSS supplier (Combustion Engineering Inc.) required staking. Valve operability failures, resulting from loosened locking nuts, have also been reported by Cooper fluclear Station (Unusual Event Report 75-5), Browns Ferry Unit 2 report of March 6,1974 and Three !!ile Island Nuclear Station Unit 1 reports of March 13, 1976 and October 20, 1976.
The corrective action by the licensee in each case was to stake the locking nut.
In June 1978, the Limitorque Corporation issued a supplement to the October 1977 issue of the Type SMB Instruction and Maintenance Manual SMBI-170 that called for the crimping or staking of the locking nuts.
The 1971 issue of the manual had statements for crimping and staking of the lock nuts incorporated into the manual. The stem nut specification drawing provided by Limitorque for Unit Types SMB-000, SMB-00, SMB-0, SMB-1, SMB-2, SMB-3, and Sf1B-4 directs the customer to a Limitorque Drawing No. 21-497-0009-3 for instructions on staking the locking nut; the specification drawing for the SMB-5 unit has a reference to Limitorque Drawing No. 21-497-0010-3 for staking instructions.
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