05000254/LER-1980-032-01, /01T-0:on 801211,during Installation of Hanger Per IE Bulletin 79-14,two 1/2-inch Anchor Bolt Holes Were Drilled Which Penetrated Primary Containment.Caused by Faulty Design.Plugs Welded in Holes

/01T-0:on 801211,during Installation of Hanger Per IE Bulletin 79-14,two 1/2-inch Anchor Bolt Holes Were Drilled Which Penetrated Primary Containment.Caused by Faulty Design.Plugs Welded in Holes

ML19340D803
Person / Time
Site:	Quad Cities
Issue date:	12/22/1980
From:	Robert Murray COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19340D801	List: 05000254/LER-1980-032, Forwards LER 80-032/01T-0 05000254/LER-1980-032-01, /01T-0:on 801211,during Installation of Hanger Per IE Bulletin 79-14,two 1/2-inch Anchor Bolt Holes Were Drilled Which Penetrated Primary Containment.Caused by Faulty Design.Plugs Welded in Holes
References
IEB-79-14, LER-80-032-01T-01, LER-80-32-1T-1, NUDOCS 8101050396
Download: ML19340D803 (2)

LER-1980-032, /01T-0:on 801211,during Installation of Hanger Per IE Bulletin 79-14,two 1/2-inch Anchor Bolt Holes Were Drilled Which Penetrated Primary Containment.Caused by Faulty Design.Plugs Welded in Holes

Event date:
Report date:
2541980032R01 - NRC Website

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60 81 DOCKET NUMB ER 68 69 EVENT DATE Je 75 REPORT DATE 80 EVENT OESCRIPT10N AND PROS A8LE CONSEQUENCE *, h ITITI l in comoliance with NRC Bulletin 79-14 a sway strut hanger was being installed in the l

lol2l l drywell on line 1-3747-8" of Reactor Building Closed Cooling Water. Two 1/2-inch l

g o l4 l l anchor bolt holes were drilled which penetrated the primary containment at a depth l

l lolai i of seven inches. There were no immediate implications concerning primary con-l t o Is l l tainment since the Unit was shutdown for a refueling outage.

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li l o I ] The cause of this occurrence is faulty desion. The desian failed to take into accounti li t i l I the relative shallowness of the concrete floor at that earticular location.

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gl consisted of seal welding plugs in the holes and a vacuum box test which was per-l 1,t31 i formed satisfactorily. The hanger was redesigned.

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LER NUMBER: LER/R0 80/32-01T-0 11.

LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill.

FACILITY NAME: Unit One IV.

DOCKET NUMBER: 050-254 V.

EVENT DESCRIPTION

On December 11, 1980, Unit One was shutdown during the Cycle Five Refueling Outage.

In compliance with NRC Bulletin 79-14, construction was in prog-ress for a sway strut hanger assembly on the Reactor Building Closed Cooling Water exhaust line 1-3747-8".

This line is located in the drywell basement, elevation 579'-10", data point approximately 550 1

While drilling two 1/2-inch diameter wedge anchor bolt holes in the concrete floor in accordance with the support assembly design, the drill penetrated the steel circular primary containment shell located about seven inches underneath the concrete floor surface.

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PROBABLE CONSEQUENCES OF THE OCCURRENCE:

Since the Unit was shutdown for refueling at :he time and primary con-tainment was not required, there were no immediate impilcations con-cerning Technical Specifications.

In addition, the breeches in the containment shell were immediately detected and reportad. Timely plans were drawn up to make necessary repairs.

Vll. CAUSE:

The cause of this occurrence is attributed to faulty design of the hanger support assembly. The original design failed to take into account the relative shallowness of the concrete floor at that particular location when it called for a drilling process which would require a penetration of approximately fif teen inches. The hanger assembly design was submitted by EDS Nuclear, Inc.

Vill, CORRECTIVE ACTION:

The immediate corrective action taken was to determine and evaluate the extent of damage to the drywell steel shell. The two 1/2-inch diameter holes were then repaired by fabricating and welding two carbon steel plugs in place of the drilled holes. The welds were inspected and a vacuum box test wcs satisfactorily performed. The plugs will be further evaluated for integrity during the next Unit One primary containment integrated leak rate test. The design of the hanger support assembly was altered so as not to require that particular anchor plate by reinforcing the main strut in another location. A thorough inspection was conducted in the drywell for any other similar type of anchor penetrations Installed since the original construction. The inspection verified that no problems existed.

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