ML19263D139
| ML19263D139 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 03/16/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Stampley N MISSISSIPPI POWER & LIGHT CO. |
| References | |
| NUDOCS 7903220010 | |
| Download: ML19263D139 (1) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION REGION 11 f
g 101 MARIETTA STREET, N.W.
r ATLANTA, GEORGI A 30303
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MAR 161979 In Reply Refer To:
RII:JPO 50-416, 50-417 Mississippi Power and Light Company Attn:
Mr. Norris L. Stampley Vice President of Production P. O. Box 1640 Jackson, Mississippi 39205 Gentlemen:
The enclosed IE Circular 79-04 in 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:
W. L. Nail, Plant Luperintendent P. O. Box 756 Port Gibson, Mississippi 39150 7 9 0 3 22 0 0 ro
UNITED STATES NUCLEAR REGULATORY COINISSION OFFICE OF INSPECTION MD ENFORCEMENT WASHINGTON, D.C.
20555 March 16, 1979 IE Circular No. 79-Oh LOOSE LOCKING NUT ON LIMITORQUE VALVE OPERATORS Description of Circumstances:
On December 8, 1978, Fort Calhoun Station Unit No. 1' 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 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 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.
This licensee was made aware of the potential problem by a letter of July 28, 1978, from the NSSS supplier, Combustion Engineering, Inc.
Other plants have reported similar findings. On April 27, 1977, Davir-Besse Nuclear Po.er 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 ihh safety related valve operators required staking. Arkansas Nuclear One (ANO), Unit 2, reported on June 29, 2978, 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 NSSS supplier (Combustion Engineering Inc.) required staking. Valve operability failures, ret ilting 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 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 Limiterque Corporation issued a supplement to the Cetober 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 fer 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, SME-3, and SMB L directs the customer tc a Limitorque 1 of 2 d
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