ML20058K669

Responds to IE Bulletin 78-09.Procedural Controls Utilized at Facility Assure That Drywell Head Reinstallations Achieve Repeatable Degree of Leak Tightness Based on Listed Reasons

ML20058K669
Person / Time
Site:	Monticello
Issue date:	07/27/1978
From:	Wachter L NORTHERN STATES POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-78-09, IEB-78-9, NUDOCS 9102130431
Download: ML20058K669 (2)

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5 NSF NORTHERN STATES POWER COMPANY MIN N E A POLIS. M S N N E S OTA 55400 l

July 27, 1978 Mr. James G. Keppler Director - Region III Of fice of Inspection and Enforcement U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

MONTICELLO KUCLEAR GENEPJsTING PLANT Docket No. 50-263 License No. DPR-22 The following is submitted in reply to IE Bulletin 78-09:

The procedural controls utilized at Monticello to assure that the drywell head reinstallations achieve a repeatable degree of leak tightness have been determined to be adequate in the past for the following reasons:

The drywell head has been reinstalled fi"e times sinceEach 1.

1973 when the reinstallation procedure was written.

of these reinstallations were followed by a local leak rate test and four of the five were followed by an No tests, local or integrated, integrated leak rate test.

have f ailed to meet acceptance criteria due to drywell head leakage.

the studs be tightened to j

2.

The procedure requires that This is accomplished using within a range of torques.

an air impact wrench with a rated torque slightly above that required by the procedure and stopping slightly Due to the before the wrench develops its full torque.

lack of available space to use a torque wrench, torque The stress in the stud, when readings are not taken.

tightened to the highest torque allowed by the procedure, is approximately 27 percent of the code allowable stress.

Determination of the suitability of the gaskets for reuse, the sequence for tightenisg the studs, the method of gasket, 3.

head, and flange preparation, and other special considerations are adequately controlled by the procedure, s

L 9102130431 780727 CF ADOCK 05000263

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N ITHERN CTATED POWER OMPANY Mr. James G. Keppler July 27, 1978 Page 2 No clearance readings between the head and the flange are taken.

Four other bolted containment closures that would tend to unseat on positive pressure are identified. These closures are the drywell head manway, the CRD manway, and the two torus manways. All the closures are local leak rate tcsted following reinstallation. When opened during a refueling outage, the closures are also local leak rate tested prior to opening. No integrated leak rate tests have failed due to leakage from these closures. There have been five integrated leak rate tests performed at Monticello.

Based on the above discussion, we believe that the procedural and administrative controls that govern the closure of containment penetrations that would tend to unseat on a positive containment pressure are adequate with two exceptions. Clearance readings between the drywell head and flange are not taken and no formal procedure exists to control the closure of the four other bolted containment closures. We will, therefore, revise the drywell head reinstallation procedure to include taking and recording the head to flange clearance. Additionally, a procedure will be prepared to control the closure of the drywell head manway, the CRD manway, and the two torus hatches.

These procedural changes will be made prior to their required use which will be during the fall, 1978, refueling outage.

Yours very truly, I

L. J. Wachter Vice President - Power Production and System Operation ec:

Mr. G. Charnoff Office of Inspection and Enforcement Washington, D.C.

20555

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