ML20155F159

Safety Evaluation Re Mixed Greases W/Greater than 5% Unqualified Contaminant in Limitorque Valve Operators. Insufficient Info Presented to Draw Conclusions

ML20155F159
Person / Time
Site:	Braidwood
Issue date:	10/06/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20155F152	List: ML20155F147 ML20155F159
References
NUDOCS 8810130173
Download: ML20155F159 (2)

Text

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ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATIhG TO MIXED GREASE 5 WITH GEEATER THAN 51 UhQUALIFIED CONTAMlhAhT IN LIMITORQUE VALVE OPERATORS COMMONWEALTH EDISON BRAIDWODD STATION - UNITS 1 AND 2

1.0 INTRODUCTION

By letters dated August 26 and September 2,1968, the licensee provided infomation on Limitorque valve operators with mixed grease (i.e., greater than 5% unqualified grease as a contaminant). Eight valve operators were found to have a heavy mixture (12% to 33% by weight) of unqualified grease (SUN EP 50). The qualified grease is Exxon Nebula EP-0 or EP-1. Samples of Exxon EP-0 and EP-1 greases of unqualified Sun EP 50 grease were mixed withat25%,

irradiated 2 x 1050% gnd Rads and75%

2 x (by 10 weighg) Rads genria to detemine the effect of radiation on their lubricating properties, as m usured by standard penetration ,

testing. Penetration tests were perfomed before and after irradiation to measure changes in the consistency of the grease mixture. Dropping point masurem-M s (temperature at which the first drop of fluid separates fram grease io a standard apparatus) were also made to detemine lubricating characteristics.

l In our SER relating to compatibility of greases in Limitorque valvo cperators (reference 1) we concluded that qualified grease with trace quantity of contaminant (2% or less) can be used in Braidwood Unit I and 2 Limitorque valve operators since at these concentrations the mixed grease is compatible and will withstand the post-accident environment. This conclusion was based upon acceptance criteria for penetration tests for the grease mixtures that were within 2 30 points of the midpoint range of the two qualified Limitorque valve operator greases (Exxon Nebula EP-0, penetration range 355-385 and Exxon Nebular EP-1, penetration range 310-340). The penetration test acceptance band was therefore 295 to 400 points. We also allowed interim operation of Braidwood Unit I with operators containing 2 to 5% contaminant based on the comitment that these operators will be regreased with qualified grease during the next refueling outage (May 1989) and upon confimation of no expgeted degradation of the mixed

. grease in a radiatic.) environment of up to 2 x 10 Rads. Ey letter dated June 23, 4

1988, the licensee provided radiation test data which showed that there was no apparent effect on lubrication properties for grease mixtures of 2 to 5% contaminant, i 2.0 EVALUATION We have, evaluated the infomation provided by the itcensee and have determined that the radiation test data on grease mixturas with greater than 25% unqualified grease provides inconclusive evidence to made a judgment on the oparability of Limitorque valve operators following an accident. In f3ct, the radiation test data raises more questions than it answers. As en example, the inboard centain-rent isolation valve for component cooling return from the number 1 seal on the reactor coolant pumps, valve ICC9438, closes within 40 seconds after initiation of I a s.ain steam line break. Theenvigonmentalconditionsatvalveclosureare300*F l containment temperature and 6 x 10 Rads. This radiation exposure considers a '

nomal 3 year dose in aridition to the accident environment. In the August 26, 1988 licensee letter, Table B indicates that 25% Sun /75% EP-1 had a loss in l fluidity as demonstrated by a penetration of 241 (54 points below the minimum

(

8810130173 SS1006 DR ADOCK 0500 g6

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', 5 of 295 for qualified grease) for an exposure of 2 x 10 Rad. Yalve ICC9438 had agreasemixturgof33% Sun /66%EP-0orEP-1(mixturenottested)andradiation exposure 6 x 10 . Would radiatio , tests of a 33% Sun /

661 EP-0 or EP-1Rads grease(exposurenottesteg)Radsyieldworkedpenetrationtestof mixture at 6 x 10 less than the 241 points for the 25% Sun /75% EP-17 Infonnation has not been provided by the licensee on the effect of less fluid grease on valve operability.

The Limitorque manufacturer recomends qualified EF-0 or EP-1 which are more fluid grease 3. Furthencore, the licensee did not provide infomation on the affects of the 300'F accidant temperature environment, in combination with the raciation exposure. This may significantly affect lubrication properties.

The test data in the licensee letter dated August 26, 1988 seems to indicate that lower-raciation expcsures may have a more deleterious effect on lubrication propertiesthanhighgrexposures,asindicatedbyincgeasesinlubricating

, properties at 2 x 10 Rads after a decrease at 5 x 10 Rads. This test data suggests that a bounding or enveloping case may not be applicable. In order to made a credible judgment on valve operator operability with a heavy mixture of urqualified grease in the qualified grease, an envircnnent qualification test ,

should bc conducted to expose the valve operator to the predicted accident environrent followed by operability testing.

- The Limitorque ranual (reference 2) ar# EPRI lubrication guide (reference 3) -

caution against mixir.g greases with different soap bases in valve optrcters (a; is the case of SUN EP 50 in Exxon EP-0 cr EP-1). Mixed grsases mcy be inccrpatible and may create problems which can effect lubrica'.ing capabilities.

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3.0 CONCLUSION

S Eased on the 3beve evaluatien, we conclude that there is insufficient it.fomation to detemine the pcst accident operability of Limiterque valve operators contain-l ing mixed grease with greater than 5% unqualified ccntaminant. Therefore,

) adecuate assurances do not exist that Braidwood Units 1 and 2 valve operators

, with more than Ei grease centaminant would have been able to perform their i

intended functicn following a Design Basis Accident.

4.0 REFERENCES

1. NUREG-1002, Safety Evaluation Report Braidwood, Units 1 & 2. Supplement #6, dated May 1988 I

2. Bulletin SMB1-82C, Limitorque Type SMS In'struction and Maintenance Manual

3. EPRI NP-4916. Lubrication Guide, Robert O. Bolt, dated January 1987