05000254/LER-1980-025-01, /01T-0:on 800913,ultrasonic Insp Revealed Crack Indications in Three Welds on Core Spray Loop a & Two Welds on Core Spray Loop B.Caused by Probable Metallurgical Failure.Elbows & Short Sections of Pipe Will Be Replaced

/01T-0:on 800913,ultrasonic Insp Revealed Crack Indications in Three Welds on Core Spray Loop a & Two Welds on Core Spray Loop B.Caused by Probable Metallurgical Failure.Elbows & Short Sections of Pipe Will Be Replaced

ML19347B348
Person / Time
Site:	Quad Cities
Issue date:	09/23/1980
From:	Dunesia Clark COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19347B345	List: 05000254/LER-1980-025, Forwards LER 80-025/01T-0 05000254/LER-1980-025-01, /01T-0:on 800913,ultrasonic Insp Revealed Crack Indications in Three Welds on Core Spray Loop a & Two Welds on Core Spray Loop B.Caused by Probable Metallurgical Failure.Elbows & Short Sections of Pipe Will Be Replaced
References
LER-80-025-01T, LER-80-25-1T, NUDOCS 8010140451
Download: ML19347B348 (3)

LER-1980-025, /01T-0:on 800913,ultrasonic Insp Revealed Crack Indications in Three Welds on Core Spray Loop a & Two Welds on Core Spray Loop B.Caused by Probable Metallurgical Failure.Elbows & Short Sections of Pipe Will Be Replaced

Event date:
Report date:
2541980025R01 - NRC Website

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9 60 61 OOCKET NUMBER 6d 69 EVENT OATE 74 75 REPORT DATE do EVENT DESCRIPTION AND PROB A8LE CONSEQUENCES h 10121 l Ultrasonic inspections revealed crack indications in three welds on the "A" core spray l g o,3, I loop and two welds on the "B" core spray loop. All indications were located in the l

g l welds and heat affected of pipe-to-elbow and elbow-to-elbow section between the l

jo;,j l reactor vessel penetration and the first manual isolation valve. Three of the crack l

IO lo i l indications had propagated through the pipe wall. However, a significant leak would jol,; ; have been detected during operation, therefore, the probable consequences are minimal.

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LER NUMBER: 80-25/01T-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 August 31, 1980, Unit One was shutdown for the end of cycle five refueling outage. As was comnitted to the NRC in LER/R0 80-06/01T-0, 100 percent of the core spray piping located inside the primary con-tainment was ultrasonic tested. The ultrasonic inspection disclosed several linear indications in three welds of "A" core spray loop and two welds of "B" core spray loop. The indications were located in the pipe-to-elbow and elbow-to-elbow welds between the reactor vessel penetration and the first manual isolation valve in both loops in the drywell. The inspection was performed by a contracted inspection firm under the direct supervision of the Commonwealth Edison Company SNT-TC-1A Level 111 Examiner.

VI.

P,ROBABLE CONSEQUENCES OF THE OCCURRENCE:

Although three of the crack indications had propagated through the pipe wall, a leak o' significant size during reactor operation would have been detected by the routine monitoring of the containment sump levels and by the routine containment atmospheric monitoring program. The core spray piping which is included in the primary coolant system boundary is inspected as part of the station inservice inspection program.

Several special inspections have also been performed, consisting of the inspec-tions required in R0 Bulletin 75-01, and an augmented inspection recom-l mended in General Electric Service Information Letter #117 The results

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of the inservice inspection and the special inspections had been j

satisfactory.

Vll. CAUSE:

The cause of the occurrence has been attributed to a probable metallur-gical failure.

Results of laboratory analysis of core spray piping that was removed f rom Quad-Cities Unit Two in the si ring of 1980 indicated that intergrannular stress corrosion crat. ng was evident, and was found to be the cause of the cracking indications.

It is reasonable to ascertain that stress corrosion cracking is the failure mode in the Unit One core spray piping also. All of the linear indications were located in the welds and heat-affected zone of the elbows. The section of piping where the indications were found is a normally stagnant line which is exposed to reactor operating pressure and elevated coolant temperatures.

The core spray oiping is type A-312, grade TP 304,10 inch, schedule 80 seamless stainless steel pipe.

The elbows are type A403, grade WP 403, 10 inch, schedule 80, seamless stainless steel elbows.

o Vllt. CORRECTIVE ACTION:

The 105 elbows will be cut out of both core spray loops as well as a short section of pipe on each end of the elbows. The elbows will be stored at the station pending future investigations. The elbows and short sections of pipe will be replaced with carbon steel piping.

Replacing the stainless steel with carbon steel piping should eliminate the probability of stress corrosion cracking in this section of the piping.

The replacement carbon steel pipe is Type SA-333, grade 6, schedule 80 seamless pipe. The fittings are Type SA-420, grade WPL-6, schedule 80 seamless elbows. The repair work will be performed under the requi re-ments of ASME Boller and Pressure Vessel Code Section XI.

The repair parts have been procured in accordance with ASME Boiler and Pressure

. Vessel Code, Section ill, Class 1.

Non-destructive testing following the repair will include 100 percent examination by radiography, magnetic partici?. or dye penetrant test of all areas adjacent to the repair welds, and 100 percent examination of the repair weld with ultra-sonics to be used as a baseline for future inspections.

Prior to reactor startup, the core spray lines will be pressure tested during the reactor vessel pressure test.

A re-inspection of the welds for both core spray loops in the drywell will be performed during the next Unit One Refueling Outage.