ML20084E363

Supplemental AO 50-237/75-11A:on 750127,core Spray Injection Line through-wall Cracks Discovered.Stainless Steel Portion of Core Spray Piping from Vessel Nozzle to Second Isolation Valve Replaced w/SA-333 Grade 6 Carbon Steel

ML20084E363
Person / Time
Site:	Dresden
Issue date:	06/29/1976
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
7388, AO-50-237-75-11, NUDOCS 8304150035
Download: ML20084E363 (5)

Text

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m ,n, o CohnMth Edison Drrden Nuclear Power Stiften VU R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920

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June 29, 1976 ,

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' q1'p-s Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations - Region III ,,

U. S. Nuclear Regulatory Commission -- ~. 1 ,

799 Roosevelt Road i Glen Ellyn, Illinois 60137 6},1-

SUBJECT:

Supplemental Report to Abnormal Occurrence Report No. 50-237/1975-11, Entitled " Core Spray Inj ection Line Through-Wall Cracks"

REFERENCES:

1. Letter from B. B. Stephenson to J. G. Keppler, dated February 6, 1975 (Report No. 50-237/1975-11)

2. Drawing Number M-27

3. Metallurgical examination of cracks in Dresden 2 BWR emergency core-spray system 10-inch diameter piping; C. F. Cheng, R. B. Poeppel, S. Danyluk, J. Y. Park /

Argonne National Laboratory REPORT NUMBER: 50-237/1975-11A REPORT DATE: June 29,1976 OCCURRENCE DATE: January 27, 1975 FACILITY: Dresden Nuclear Power Station, Morris, Illinois INTRODUCTION The final report on the metallographic examinations of the Unit-2 stainless steel core spray piping weldments vb1 completed in April, 1976 by Argonne National Laboratory. Based on the Argee report, the following supplement to the original abnormal occurrence report 4's en prepared.

DESIGNATION OF APPARENT t,\USE c OF GCCURRENCE A total of eight weldments were found to be defective in the two loops of the core spray system. Four of the eight welds were examined in detail by Argonne, three others were sent to General Electric, and one was retained by Commonwealth Edison. The attached Table A summarizes the varfous crack data for all eight defective welds. Figures 1 and 2 give the locatiuca of the cracked joints.

Conclusions of the Argonne study are as follows:

i:.5 a) The cracks were generally circumferential and were located in the heat-affected zone near the welds 8304150035 760629 en-n-= D.I.Wmn

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Mr. Jamsa G,9pplar0 00 June 29, 1976 b) The mode of failure was strictly intergranular stress corrosion, initiating at the I.D. surface and propagating toward the 0.D.

c) Fatigue striations were not observed on the cracked surfaces by scanning electron microscopy

! d) None of the cracks propagated through welds, but were limited to a I

penetration of about 0.2 inches l

l e) The cracks were similar to those found in 4-inch recirculation bypass lines, even in the relative composition of corrosion products.

CORRECTIVE ACTION Corrective action taken to prevent recurrence was to replace the stainless steel portion of the core spray piping from the vessel nozzle to the second isolation valve with SA-333 Grade 6 carb'.a steel, and to replace the reactor vessel core spray safe-ends with SA-182 type 316L stainless steel with I.D.

cladding of 308L weld material, jf,.y} fl{2.-- ! ,

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Station Superintendent Dresden Nuclear Power Station BBS:JBM:jo

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I TABLE A. _

Summary of CracLa in 10-in. Core-spray Piping of Dresden-2 SWR Location Description Length Haz.  ;

Weld- at ID Depth Remarks Lo0P Component of ment c -' E'*d:.'":' Distance"g";ido> <ia > -

l Longitudinal 3:30 1/4-1-1/2 1-1/4 Leak Sant to CE ,

10-2 Safe End '

Longitudinal '8:30 1/2-1-3/4 1-1/4 1.e ak -

G Longitudinal Sent to CE Dutchman and Multiple 0-3/4 - -

Circumferential ,

10-24 3 i 10:30 0-1/2 >1/2 Leak -

,,,, gig, Lonsitudinal

• • Weld 10-24 4 - -

Circumferential Hultiple -

l' 12:00 3/8 0.8 0.07 Sent to CE 10K16 ' Y-8h8Pe d1

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3

.I Elbow Side Longitudinal 7:00 - - 0.4 - h -

Weld 10K14, or U-shape [

10K14 I e Side U-shape 7:00 0-3/8 3/4 0.28 -

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Pipe Leak j .

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. S, 10-25 Both Sides Circumferential Multiple 0-1/4 at Wald 10-25 11:30 l g, [

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10E5 (Iy Circumferential. - 1/8 - -

by C I

10-2 Safe End Longitudinal 4100 1/4-1-1/8 - - Sent to CE

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Leak 10-28 Dutchman Circumferential 10:00-12:30 0-1/4 5-1/4 at Sant to CE I 11:30

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. NOZZLE N-19A g .

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i SAFE END 10 - 2 s DUTCHMAN .

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The weldments ,

Fig.'1. Loop A Emergency Core-spray Piping of Dresden-2 BWR.~ Crack areas are are indicated by dashed circumferential lines.

denoted by arrows and weld identification numbers. _ .__ . , _

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NOZZLE NI98 7

DUTCHMAN

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l Loop B Emergency Core-spray Piping of Dresden-2 BWR. The'veldments ,

Fig. 2, <

are indicated by dashed circumferential lines. Crack areas ara I denoted by arrows and weld identification numbers.

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