ML20084B110

Ao:On 730426,MSIV 22 Failed to Close in Response to Manual Signal by Control Room Operator.Caused by Binding of Linkage Connecting Solenoid Armature to Valve.Solenoids Thoroughly Cleaned of All Lubricant

ML20084B110
Person / Time
Site:	Indian Point
Issue date:	05/04/1973
From:	Zarakas P CONSOLIDATED EDISON CO. OF NEW YORK, INC.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8304060123
Download: ML20084B110 (3)

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Ccrisul J3ted E J son Ccmmy of New Ycrk. Inc.

4 iteroj P:i.e. M W Yr,rk. N Y 1000 3 TWr.L cre (212) 400 5181 May 4, 1973 Re: Indian P.oir,t Unit No. 2

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Docket No. 50-24.

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Mr. John F.

O' Leary, Director Directorate of Licensing C

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S. Atomic Energy Commission

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Dear Mr.

O' Leary

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This report of an Abnormal Occurrence is submitted in accord-ance with the requirements of Section 6.6.1 of the Unit No. 2 Technical Specifications:

On April 26, 1973 at approximately 8:30 A.M., Number 22 Main Steam Line Isolation Valve failed to close in response to a manual signal initiated by the Control Room Operator. The signal was initiated for the purpose of testing valve closure time. At the time of the occurrence, the reactor was shutdown with all control rods inserted. The Reactor Coolant System 0

pressure and temperature were 2235 psig and 525 F, respect-ively, and the reactor coolant boron concentration was 1790 ppm.

With this concentration of boron and all control rods fully inserted, the reactor was suberitical by at lcast 10 percent delta k/k.

Initial investigation of the occurrence revealed that both of l

the solenoid-opeinted air cylinder exhaust valvas (two in I

parallel) failed to opan.

The remaining three Main steam Line Isolation Va(ves were __

also tested and these results werc found to be satisfactory.

nowevor, it was noted that onlv one of the two air exhaust solenoids associated with Nos. 23 and 24 Main Steam Line Isolation Valves functioned.

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M r. John F. O' Leary May 4, 1973 Description and Evaluation of Safety Implications Each of the steam generators is equipped with an isolation valve in its main steam line. These valves contain a free swinging disc which is normally held up out of the main stean flow path by an air piston. The isolatior. valves are automatically closed upon receipt of a signal from the steam line break protection system as described in Section 7 of the PSAR. They may also be closed by manual action.

The safety implications of this occurrence stem primarily from nho fact that four out of sixteen solenoid valves failed to function properly, and not the fact that one isolation valve failed to close. This is so because: (1) there was no actual steam break, and it was, therefore, not essential that the isolation valve close, (2) the safety analysis presented in Section 14.2.5 of the FSAR shows that the core is protected even if one of the four isolation valves should fail to close, and (3) a repeat failure of four solenoids, in a certain combination, could result in two steam line isolation valves not closi;g in response to an actual pipe rupture signal. If the postulated pipe rupture was a large one downstream of the iso.lation valves, the related safety effect could be significant.

Detennination of cause Each of the four subject solenoid valv,es was thoroughly exam-ined to determine the cause of its malfunctioning. On the basis of these examinations, it has been concluded that the cause was the same in each case, and that each of the mal-functions resulted from binding of the linkage connecting the solenoid armature to the valve it is intended to operate.

The binding was caused by a combination of hardening of the lubricant used at the several pivot points associated with each solenoid, and contamination of the lubricant through long-term exposure to the dest-laden air commonly caused to exist at a cons ;ruction site.

Corrective Action to Prevent Recurrence As a means for preventing recurrence, the linkage associated with each of the four subject solenoids has been thoroughly cleaned of all lubricant. In addition, the lubricant is to be removeu irca une remaining twelve solenota valves prior to initial cri ticality of the reactor, u

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Mr. John F. O' Leary May 4, 1973 A reevaluation as to the need for lubrication has been made, and we have concluded that none is required in this particular application. The solenoid linkage will, there-fore, be left free of lubricant to prevent recurrence.

To assure that the potential for similar malfunctions does not exist elsewhere within the Unit No.2 facility, we are currently reviewing the records to determine in what other applications this type of solenoid has been employed. In any case where the same or similar solenoid is used, we will take steps to remove all traces of lubricant.

2 Each of the solenoid valves will be thoroughly tested to insure its operability following the above described correct-ive and preventive maintenance efforts. In addition, periodic inspection of solenoid valve linkage is to be incorporated in our preventive maintenance program.

Conclusion Although, as stated previously, a malfunction of four of the sixteen solenoid valves associated with the Unit No. 2 main ateam isolation valves carries with it safety implications, we do not believe the probability of recurrence is significant.

The cause of these particular malfunctions was identified,. and the principal ingredient necessary to cause repetition, i.e.,

the lubricant, either has been eliminated or will be within the next several days. Our Nuclear Facilities Safety _ Committee reviewed the circumstances relating to this abnormal occurrence and has approved the corrective measures instituted as a result thereof.

1 Very truly yours gh

,Y A

i Pe er rakas Assistant Vi e President l

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