05000298/LER-1982-014, Amended LER 82-014/03X-1:on 820607,rejectable Indications Found in Heat Affected Zones of Welds BJ-13,BJ-15,BJ-20 & BJ-23.Caused by Improper Fabrication Techniques.Affected Piping & Fittings Replaced

Amended LER 82-014/03X-1:on 820607,rejectable Indications Found in Heat Affected Zones of Welds BJ-13,BJ-15,BJ-20 & BJ-23.Caused by Improper Fabrication Techniques.Affected Piping & Fittings Replaced

ML20077D109
Person / Time
Site:	Cooper
Issue date:	02/03/1983
From:	Freborg S, Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
CNSS830073, LER-82-014-03X, LER-82-14-3X, TAC-51699, TAC-52037, NUDOCS 8307260357
Download: ML20077D109 (5)

LER-2082-014, Amended LER 82-014/03X-1:on 820607,rejectable Indications Found in Heat Affected Zones of Welds BJ-13,BJ-15,BJ-20 & BJ-23.Caused by Improper Fabrication Techniques.Affected Piping & Fittings Replaced

Event date:
Report date:
2982082014R00 - NRC Website

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REPORT DATE EVENT DESCRIPTION AND PROO ABLE CONSEQUENCES h 10121 l During the replacement of RWCU-MO-15 (6"-900 lb. aate valve). reiectable indications 1 0 3 l were found in the heat affected zones of welds BJ-13, BJ-15, BJ-20, and BJ-23. (Ref- l 1014 l l erence CNS ISI Drawina #3) The reactor was in the refueling mode of operation when the1 0 5 i event occurred. This event is not repetitive. There were no adverse effects on the 1 0 6 l"public health and safety. 1 O i i I O 8 l l DE CODE SU8C E COMPONENT CODE SUB ode SU E O 9 e

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Mr. John T. Collins, Regional Administrator b U.S. Nuclear Regulatory Commission I-- '

Region IV

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611 Ryan Plaza Drive _j ,

y Suite 1000 2 Arlington, Texas 76011

Dear Sir:

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This amended report is submitted in accordance with Section 6.7.2.B.4 of the j Technical Specifications for Cooper Nuclear Station and discusses a reportable -

occurrence that was discovered on June 7, 1982. An amended licensee event  ;

report form is also enclosed.

4 E

Report No.: 50-298-82-14-01 i Report Date: February 3, 1983 -

Occurrence Date: June 7, 1982 Facility: Cooper Nuclear Station .

Brownville, Nebraska 68321 2 A

m Identification of Occurrence: i A condition was discovered which indicated an abnormal degradation of the y Class IN Reactor Water Clean-up (RWCU) System pressure boundary inside  ;

primary containment. =

Conditions Prior to Occurrence: -

The reactor was in the refueling mode of operation.

Pj Description of Occurrence: -

During the scheduled replacement of RWCU-M0-15, a six inch 900 pound 3 austenitic stainless steel Anchor Darling gate valve, rejectable indica- ]

tions were detected in the heat affected zones (HAZ) of welds BJ-20 and 23 (reference CNS ISI Drawing #3). The indications were detected by $

liquid penetrant examination on the inside diameter of welds BJ-20 and 23 s near the valve. Subsequent examination of the balance of six inch welds

• on the RWCU line also produced rejectable indications in welds BJ-13 and N

15. The rejectable indications in welds bJ-13 and 15 were detected by 3 ultrasonic (UT) examination. 3 1

Designation of Apparent Cause of Occurrence: i The cause of the indications in BJ-13 and 15 were attributed to improper j fabrication techniques and are not considered service induced. The "

rejectable transverse indication in weld BJ-13 was present on the

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original construction radiograph while weld BJ-15 was rejectable due to n . lack of fusion in the weld joint.

The. failure mode in welds BJ-20 and 23 has been' identified as.

Intergranular Stress Corrosion Cracking (IGSCC), due to weld joint sensitization. Failure analysis.was performed by Rockwell International under the direction of.the Electric Power Research Institute (EPRI). A detailed report is available from EPRI.

' Analysis of Occurrence:

The RWCU. System provides a method of purifying the primary coolant water

~

by continuously removing a portion of the Reactor Re' circulation (RR)

System' flow from RR "A" loop via a 20" Residual Heat Removal (RHR) System suction line. RWCU piping and fittings are 6" schedule 80, Type 304' austenitic stainless steel.

BJ-20 had several circumferential indications in its HAZ. Two transverse indications were present in the HAZ of BJ-23. At the time of occurrence, there'was speculation that the indications were IGSCC. This has been.

verified through failure mode analysis conducted by the Rockwell Interna-tional Science. Center for EPRI. This analysis has determined the cause

~

of IGSCC to be weld joint sensitization, therefore it is concluded that failure was not service induced. .These two weld failures are the first

. cases of IGSCC in this. plant.

One hundred percent of accessible six inch welds from the upstream weld on the outboard isolation valve (RWCU-H0-18) to the attachment weld'on the 20" RHR suction line were examined by UT. The UT procedure used was

-the same procedure that is used to detect IGSCC. Examiners qualified to this procedure had previous training on cracked pipe specimens exhibiting IGSCC. Due to their microstructure, austenitic stainless steels have a

" leak before break" characteristic.' Therefore, had the indications degraded to a " leak before break" condition, drywell leak detection systems would have detected such leakage.  ;

The reactor was in the refueling mode of operation when this event was discovered. .This occurrence presented no adverse consequences concerning

.public health and safety.

- Corrective Action:

The piping and fittings affected by the rejectable welds were replaced.

The pipe was replaced by material identical to that used in construction.

Fittings used were Type 304L, low carbon nuclear grade. fittings rather than the' Type 304 fittings e ad in plant construction. Measures were taken to control-heat input to the replacement welds, to avoid sensi-tization of the weld joints.

Mr. John T. Collins

. _ February 3, 1983 Page 3 1

i The scope of Augmented ISI:for the 1983 refueling outage is being in-creased in view of cracking being experienced in primary coolant, service sensitive piping at other operating BWRs.

1 Sincerely,'

L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attach ~.

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