RBG-34034, Forwards Reassessment of Indication on Riverbend Feedwater Nozzle (N4A) to Safe End Weld

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Forwards Reassessment of Indication on Riverbend Feedwater Nozzle (N4A) to Safe End Weld
ML20072P933
Person / Time
Site: River Bend Entergy icon.png
Issue date: 11/19/1990
From: Odell W
GULF STATES UTILITIES CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20072P934 List:
References
RBG-34034, NUDOCS 9011290300
Download: ML20072P933 (4)
v • d • e


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' GULF STATES UTELITIES COMPANY MWE D Bt ND $1 Ah0hi PO51 OF8tCf BOA 270 Ff f RANCt$VILLE log @As.A 70776 Aftt A CODE bN 035 6394 346 4861 Novmber 19, 1990 RBG-34034 File Nos. G9.5, 224.600 U. S. Nuclear Regulatory Ctzmtission Document Control Desk Washington, D.C. 20555 Genticnent e

River Bend Station - Unit 1 Docket No. 50-458 Enclosed are Gulf States Utilities Company's (GSU) results of ultrasonic testing (W) conducted on the N4A-2 feedwater nozzle-to-safe end weld during the third refueling cutage (RF-3) <

at River Bend Station. An indication was identified in this weld during the second refueling outage (RP-2). As a result a mid-cycle inspection was perfomed as ccmmitted - in our letter fran Mr. J. E. Booker to you dated May 15,- 1989 (RBG-30833) and -

supplenented May 19,- 1989 (RBG-30922). The results of the_

. mid-cyclo examinations were suhnitted to the staff in our Ictter

. frm Mr. W. H. . Odell dated March 21, 1990 (RBG-32527). Three examinations were. performed during the third refueling outage.

Synopses of each examination are provided in Enclosures 2 and 3. _l The- results .of these inspections revealed an increase in flaw -l

. length of 1.1 inches, and an - increase in flaw ' depth - of - 0.13  ;

w ' inches. . A' chronology of the 'TT examinations performed on this weld is provided in Enclosure 4. An analysis of the results . of >

co tho' RF-3 trr examinations has been performed by the GE Company and _ [

4 are provided in Enclosum: 1.

, Inservice Inspections (ISI) were performed in' accordance with  ;;

ASME Cbde Section XI and Generic letter 88-01. The augnented '

' inspection conducted at River Bend Station- (RBS) during RF-2

. identified. an- indication'in the N4A-2 feedwater inlet nozzle to '

u - safe 'end weld.. A ciretnferential indication, as shown in Figure 1: .of Enclosure .1, was identified on the safe end wld, in the buttered area. The indication was detected and sized by. manual  ;

examination to be approximately 6.125 inches-long, with a traxinum

-' depth of approxinately 0.2 inches and an. average depth of _ 0.16

  • L inches. Manual and 'autcmatic (P-Scan) ultrasonic examinations  !

were conducted on the N4A-2. nozzle during the cycle 3 mid-cycle t

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9011290300 901119 PDR ADOCK 05000458 [ l P PDC (

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! Page 2 of 4 -  !

[ outage (NCY-3) . - The results of these inspections revealed. no yw increase in ' depth of the indication, and the length of the indication had increased 0.5 inches to a total _ length of 6.625

' inches. The nanual and P-Scan examinations perforned during RP-3 recaled that the indication had grown to a naximum length of 7.7 incht.'t and .to a naximum depth of 0.33 inches as shown in Enclostee 2. Figure 2 of Enclosure 1 shows a depth profile of the indication at FF-2 and RF-3.

I' 2he nozzle-to-safe' end- weld received nanual and autcxtatic p ultrasonic exantinations by EBASCO Services Inu. and a-nanual J ultrasonic examination by Hollier Associates during RF-3. These

. exantinations were ccrupleted November 11, 1990. Attachnent 1 to N Enclosure 2 sumrarizes the nothods used by the examiners during

.their inspoetions. Below are the findings of each- examination t- perfeImed : i

1. - Manual Ultrasonic Examination by EBASCO Services .Inc.  !

(Enclosure 2):: 4 The-indication-was detected and sized to be a naximum of 7.7 h

inches long, with a maximum depth of approxinately 30 percent through-wall (0.33 inches) and an average- depth of  ;

15; to ' 20 percent through-wall (0.165 to 0.22 inches) along i e the length of -the indication with . branching effects of

,n ;  ; measurable depth.  :

y, . .

( 2. 1 Autcznated : Ultrasonic Examination (P-Scan) -by EBASCO Services

-Inc. - (Enclosure 2)

  • LThe . indication was' detected and sized to .beiapproximately 16.93-' finches long, with a maximtun depth-:of approxinately 25 b r y* , % . percent through-wall- (0.275 -inches): and an average depth -of D '15 to . 20 percent. through-wall '(0.165 to 0.22 inches)' along d' n ,
  • _theilongth of1 .the iindication with -branchingD effects of.

,y.  : measurable effects. - ,  ;

w , , ,

3.
iManual Ultrasonic Examination by Hellier Associates y yi , (Enclosure 3): il 4 -The4 indication was detected and sizedJto be approximately;  ;

17.62511nches, with :a Omaximumd 1 epthl of . approxinately 30 l N,

Lpercent through-walli (0.~33 inches) J u s t i

.Not e: _100 percent'through-wall depth is l'.1: inches. 1 m- . Based ,upon> ' the ' results frun the aforamentioned ! inspections and U' evaluations-'of the examination data' sheets, GSU' has determimd 1 d that 'Dere was indication growth of approxinately:0,13 inches in

depth (18 tol3_0 percent' through-wall) and 1.1 inches in length .- .

g - (17.6 to 20.'4 percent pipe circumference) since MCY-3. l

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Page 4 of 4 In accordance with the reporting requimnents of Generic letter 88-01, this evaluation of the subject weld indication and the assessnnnt of growth rate is provided for your review and approval. Docause the unit is scheduled for restart Novemter 25, 1990, your pronpt attentien to this subnittal is requested.

If you need any additional infonnation, please contact Mr. Icif L. Dietrich of my staff at (504)381-4866.

qsr I

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i. e Manager-River Bend Oversight 4

River Bend Nuclear Group.

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cc:: U. S. Nuclear IMgulatory Cmmission 611 Ryan Plaza Drivei Suite 1000' '

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Page 3 of 4 Wis indication exhibits faceting and branching, multiple peaks, short pulse durations, fast rise and fall tdne, etc., which are indicative of IGSCC. From this determination, GSU is treating the N4A-2 feedwater nozzle-to-safe end wld as an IGSCC Category "F" weld addressed in NRC Generic Ictter 88-01. This wld shall be examined under the guidelines set forth in the generic letter and shall be addressed in the RBS ISI Plan.

We RF-2 indication depth and the indication depth based on the PS-3 UI' are shown in Figure 6 of Enclosure 1. It is seen that the overall growth in the indication over the past cycle is wll L below the predictions in the analysis provided in our letter dated May 15, 1989. The predicted indication growth rate, based on the wrst case reactor water conductivity,used to detennine indication growth during the fourth fuel cycle is 5.0 E-5 in/hr.

Wis valve bounds the growth rate estinated from the MCY-3 and RF-3 UT sizing (2.89 E-5 in/hr). It can be seen that the conservatively estinated flaw size after 7000 hours0.081 days <br />1.944 hours <br />0.0116 weeks <br />0.00266 months <br /> of operation y would be 0.68 inches compared to the ASME Ccde allowable value of 0.825 inches. Based on the evaluation of the condition, GSU has determined that operation until the mid-cycle outage, scheduled

-for the latter half of September, 1991 is acceptable in the current condition. In addition to this evaluation, GSU will take the following corrective actions:

t 1. The subject feedwater nozzle wld will be re-examined during the mid-cycle outage planned for cycle 4. This outage is currently scheduled for approximately 7000 hours0.081 days <br />1.944 hours <br />0.0116 weeks <br />0.00266 months <br /> of operation after startup from RF-3. This corresponds to the latter half of September, 1991. The results of the mid-cycle examination and evaluation of the data will be provided to the NRC along with descriptions of any further corrective actions.

Materials and personnel will be staged to permit repairs to this weld should the mid-cycle nuasured indication depth and length be found outside the tuinds of the analysis.

2. The subject feedwater nozzle wld will also be m-examined during the fourth refueling outage per the requirennnts of Generic Intter 88-01. This will allow further determination and verification of growth of the
indication, if any, r
3. GSU is planning to join the recently developed EPRI Nozzle / Safe-End Pesearch Program. This research program addresses the evaluation of repair, replacenent, msidu211 stress mitigation and examination approaches

- for boiling Water Reactors nozzle to sa fe-end configurations that use Inconel 182 wld filler materials.

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Page 4 of 4 In accordance wiOi Ole reporting requirenents of Generic Intter 88-01, this evaluation of the subject weld indication and Ole assesment of growth rate is provided for your review and approval, recause the unit is scheduled for restart Novanber 25, 1990, your pronpt attention to this subnittal is requested.

If you nood any additional infornation, please contact Mr. leif L. Dietrich of my staff at (504)381-4866.

Q

f. ' ell Manager-River Dend Oversight River Dend Nuclear Group I d LLD/M. /pg Attachments cc U. S. Nuclear Regulatory Conmission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 Ms. Claudia Abbate U. S. Nuclear Regulatory Cantission 11555 Rockville Pike Rockville, MD 20852 NRC Resident Inspector Post Office Box 1051 St. Francisville, IA 70775 1

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