ML19263D143
| ML19263D143 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 03/16/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Mary Johnson SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 7903220017 | |
| Download: ML19263D143 (1) | |
Text
UNITED STATES
- g* "8009 NUCLEAR REGULATORY COMMISSION
- o REGloN ll o
5 10t MARIETTA STREET,N.W.
8 ATLANTA, GEORGIA 30303 o,sa..../
MAR 161979 In Reply Refer To:
RII:JP7 50-395 South Carolina Electric and Gas Company Attn:
Mr. M. C. Johnson, Vice President and Group Executive - Special Services and Purchasing P. O. Box 764 Columbia, South Carolina 29218 Gentlemen:
The enclosed IE Circular 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.
~
James P. O'Reilly b
Director
Enclosure:
IE Circular No. 79-04 cc w/ encl:
A. A. Smith Quality Assurance P. O. Box 8 Jenkinsville, South Carolina 29065 T. B. Conners, Jr.
Conners, Moore and Corber 1747 Pennsylvania Avenue, N. H.
Washington, D. C.
20006 O. S. Bradhan., Manager Nuclear Operations P. o. Box 8 Jenkinsville, South Carolina 29065 79032200M
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
2055 March 16, 1979 lE Circular No. 79-04 LOOSE LOCKING NUT ON LIMITORQUE VALVE OPERATORS Description of Circumstances:
On December 8, 1978, Fort Calhoun Station Unit No. l' reported that 30 out of 65 Limitorque 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 tne stem nut to move axial.'y to the point that the splines are disengaged; resulting in a loss of drive to the valve stem. The licensee 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.
Thic licensee was made aware of the potential problem by a letter of July 28, 1978, from the USSS supplier, Co=bustion 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 s total of 65 out of ihh safety related valve operators required staking. Arkansas Nuclear One ( ANO), Unit 2, reported on June 29, 1978, that several valve operators required staking. A subsequent inspection at ANO Unit 2 vas made by an IE inspector who identified records that 15 out of 17 SMB operators provided by the NSSS supplier (Combustion Engineering Inc.) required staking. Valve operability failures, resulting from loosened locking nuts, have also been reported by Cooper Nuclear Station (Unusual Event Report 75-5), Browns Ferry Unit 2 report of March 6, 197h and Three Mile Island Muclear 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 Limiterque Corporation issued a supplement to the October 1977 issue of the Type SME 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 nac apecification drawing provided by Limitorque for Unit Types SMP-000, SMB-00, SMB-0, SMB-1, SMB-2, SMB-3, and SMB L directs the customer to a Limitorque 1 of 2 7903210092 3dk
-