ML20084J240

Ro:On 720923,during Visual Insp,Vacuum Breakers 1601-33A,32C & 32D Found to Be Open.Counterweight on Valve Shaft Changed to Provide Greater Closing Moment on Valve Disc

ML20084J240
Person / Time
Site:	Quad Cities
Issue date:	10/03/1972
From:	Palmer F COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084J218	List: ML20084J216 ML20084J240 ML20084J296 ML20084J305
References
72-188, NUDOCS 8305120265
Download: ML20084J240 (2)

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• Comm ealth Edison

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M -$lb g Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of 1.icensing US Atomic Energy Commission Washington, D.C. 20545

REFERENCE:

Quad-Citics Nuclear Power Station; Unit i, DPR-30 Appendix A; Sections 1.0.A.2, 1.0. A.4, 3.7. A.4, and 6.6.3.3

Dear Mr. Giambusso:

The purpose of this letter is to report a condition relating

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/ to the operation of the station, in which, three Unit I suppression chember to drywell vacuum breakers were found

(, (u[{ to have an incorrect position indication when visually inspected.

The reactor had been shutdown and cooled down for the purpose YI. of entering the torus to conduct this inspection. This condition was reported to you by telegram on September,25, 1972.

gV'-, pg, OESCRIPTION OF INClDENT On September 23, 1972 the Unit 1 torus was entered in order to inspect the suppression chamber to drywell vacuum breakers.

This inspection was deemed necessary based on the problems experienced with the Unit 2 vacuum breakers reported to you j in my letter of September 6,1S72. Although all valves

' indicated fully closed at the test panel, 3 valves were found to be slightly open. Valves 1601-33A and 1601-32C were cach open 1/16 of an inch and valve 1601-32D was 3/4 of'an inch open. All valves were then cycled once from the remote test panel to verify ope.rability.

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b U i .The valves a11' opened properly, however,.six valves did not return to the' fully closed position. The discrepancies were as follows:

Valve No. . Remote Indication- Actual Position 1601-32A Not closed 1 1/2" open 1601-320 , closed 1/2" open.

1601-32E Not closed 3 1/4" open 1601-33A Closed

• 1 1/4" open 1601-33B Closed 1/16" open 1601-33C Closed 1/8" open CORRECTIVE ACTION A design modification was made on all the Unit i vacuum breaker valves which should significantly improve their performance.

I The position of the countenacight on the valve shaf t was changed to provide a greater closing coment on the valve disc when it is at a position near its seat. This was accomplished without affectin~g. the normal valve operation.

The valves will still go fully open at a differential pressure of less than .5 psi. This modification has also been made to the Unit 2 valves.

After the valve repairs and moillfications were completed, the following tests were performed:

1. Valves were opened with a torque wrench to demonstrate the .5 pst differential criteria. This was repeated 5 times on each valve.

2. The valves were manually opened 1/2 Inch and then released to show that'there is no tendency for the valve to " hang up" when moved slightly off the seat.- This was also repeated 5 times on each valve.

3. Each valve was then cycled 10 times f rom .the remote test panel and its position indication checked.

A leakage test was also performed by pressurizing the drywell

~to .8 psi.and visually inspecting the vacuum breakers'and pressure suppression piping in the torus. -The drywell pressure was maintained easily with the torus open and only two minor leaks ~were detected on the valves.

Very.truly yours, L

E.- Commonwealth Edison Company

-Quad-Cities Nuclear Power Station

F. A.' Palmer' Superintendent . l

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