ML20205Q372

Forwards Rept on Final Disposition of Ultrasonic Indications Identified During Insp of Unit 2 Steam Generators & Pressurizer & WCAP 11063 & WCAP 11064 Re Steam Generators & Pressurizers

ML20205Q372
Person / Time
Site:	Byron
Issue date:	05/21/1986
From:	Ainger K COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20205Q374	List: ML20205Q372 ML20205Q398 ML20205Q416
References
1700K, NUDOCS 8605280272
Download: ML20205Q372 (10)

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Commonwealth ECson O One First National Plaza, Chicago. Ilhnois g

i e O Addrgss Rrply to: Post Office Box 767 Chicago Illinois 60690 May 21, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Byron Station Unit 2 Preservice Inspection Steam Generators and Pressurizer NRC Docket No. 50-455 i

Reference (a): October 11, 1985 letter from K. A. Ainger to H. R. Denton

Dear Mr. Denton:

Reference (a) provided Byron Unit 2 preliminary preservice inspection data for the steam generators and pressurizer. This information included details of weld repair and metallurgical analyses, some official preservice inspection data, and fracture mechanics analyses of the steam generator welds based on the preliminary examination data.

Hydrostatic testing and the entire official preservice inspection of the Byron Unit 2 steam generators and pressurizer have now been completed.

The fracture mechanics analyses of the steam generators and the pressurizer

[ using the official data have also been completed. Commonwealth Edison has dispositioned all weld indications based on the official inspection results i and fracture mechanics analyses. The enclosed report provides en==nnwealth

- Edison's final conclusions regarding these inspection efforts and analyses.

The official preservice inspection of Byron Unit 2 was performed to i the requirements of ASME Section XI 1977 Edition with addenda through Summer 1978 Addenda. Based on the official inspection data, all indications have been characterized as either unacceptable surface indications, unacceptable subsurface indications, or acceptable indications.

'Nelve indications in component welds remain unacceptable to Section XI requirements. These indications have been identified as very small innocuous slag inclusions which are expected to have an insignificant affect on vessel weld integrity. Due to the location of the indications, their removal and subsequent weld repair involves potential significant risk to vessel integrity. As a result, commonwealth Edison does not intend to remove the twelve indications per Section XI preservice inspection require-ments and is hereby requesting appropriate waivers from section XI for this.

8605200272 960521 PDR G ADOCK 05000455 /

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H. R. Denton May 21, 1986 A description of the steam generator fracture mechanics analyses was provided previously in reference (a). A more detailed description of the analyses for the steam generators, and the analysis for the pressurizer, is provided in the enclosed report. This report also addresses concerns of the NRC which were discussed in a conference call with Commonwealth Edison on February 25, 1986.

The enclosed report contains two Westinghouse WCAPs which document

'the fracture mechanics analyses. These WCAPs are the technical basis for the handbook, and the handbook itself, for use in evaluating flaws in the Byron Units 1 and 2 steam generators and pressurizers. Westinghouse has reviewed the applicability of these WCAPs and concluded they are equally applicable to the steam generators and pressurizers installed in Braidwood Units 1 and 2.

With respect to the twelve unacceptable indications which are not planned for repair, Commonwealth Edison intends to perform augmented inservice inspections of these indications to confirm they do not grow to critical sizes during plant operation. These inspections will be conducted in accordance with the pertinent requirements of ASME Section XI.

Please direct any questions regarding this matter to this office.

One signed original and fifteeen copies of this letter and the enclosure are provided for NRC review.

Very truly yours, K. A. Ainger Nuclear Licensing Administrator la Rnclosure cc: D. Danielson - NRC Region III 1700K E -U

. s REPORT ON FINAL DISPOSITION OF ULTRASONIC INDICATIONS IDENTIFIED IN BYRON UNIT 2 STEAM GENERATORS AND PRESSURIZER Reference (a): October 11, 1985 letter from K.A. Ainger to H.R. Denton Introduction preliminary preservice inspection examinations, performed prior to system hydrostatic testing, identified 45 ultrasonic indications in welds of the Byron Unit 2 steam generators and pressurizer. Supplemental non-destructive examinations, weld sampling and metallurgical analyses were subsequently performed to determine the nature, cause and actual sizes of the indications. Additionally, eight weld indications were removed by grinding. It was concluded that the weld indications are small slag inclusions formed during the fabrication process. The slag inclusions are located between weld pass interfaces. The metallurgical analyses demonstrated that ultrasonic examination techniques exaggerated the length and through-wall dimensions of the indications by at least a factor of two.

preliminary preservice inspection data, details of weld repair and metallur-gical analyses and some official preservice inspection data were provided in reference (a). Fracture mechanics analyses of the steam generator welds using the preliminary examination data were also provided. These analyses demonstrated that the indications in the steam generator welds would not grow to unacceptable sizes during the forty year plant life.

Hydrostatic testing and the entire official preservice inspection of the Byron Unit 2 steam generators and pressurizer have now been completed.

The official examination data have been evaluated for acceptability to ASME Section XI requirements. Fracture mechanics analyses of the steam generators and the pressurizer utilizing the official data have also been completed.

Commonwealth Edison has dispositioned all weld indications based on the official inspection results and fracture mechanics analyses. This report provides Commonwealth Edison's final conclusione regarding these indications.

Official preservice Inspection The official preservice inspection at Byron Unit 2 was performed to the requirements of ASME Section XI 1977 Edition with addenda through Summer 1978 Addenda. The ultrasonic inspection data includes 47 weld indications listed in the attached tables. Forty-five of these indications were originally identified during the preliminary inspection. Two additional indications were found during the official inspection. All indications, except those removed by grinding or core sampling, have been characterized as unacceptable surface (Table A-1), unacceptable subsurface (Table A-2) or acceptable (Table A-3) based on the official inspection data. preliminary examination data is provided in the tables for indications which were removed, since these indications could not be re-examined during the official inspection.

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Surface Indications Unacceptable to Section XI, Table IWB-3511-1 Table A-1 lists 10 surface indications in steam generator welds which exceed the requirements of Section XI Table IWB-3511-1. Seven of these indications were removed prior to secondary system hydrostatic testing.

The remaining 3 indications were resized during the official inspection.

The examination results (indication sizes) were essentially the same as the preliminary inspection results. Therefore, these 3 indications remain unacceptable to Section XI.

The preliminary inspection identified 7 other surface indications unacceptable to Section XI (see reference (a), Table A-1). Six of these indications are located in steam generator secondary side welds. Prior to-the secondary system hydrotest, portions of the welds inner diameter (I.D.) surfaces were visually examined. These visual inspections identified the source of the 6 indications as I.D. surface geometry.

Consequently, these indications are not reportable per Section XI requirements. . The remaining indication is located in the pressurizer upper shell-to-lower middle shell weld #PC-03. In this case, the indication source was not identified as a weld " defect", but as backscatter from the stainless steel clad to carbon steel interface.

Indications of this nature are commonly referred to as " clad roll" when viewed on the ultrasonic display screen. Similar indications were reported intermittently around the entire 360 degree weld circumference.

This condition is also not reportable per Section XI requirements. All 7 additional indications are now identified as acceptable in Table A-3 of this report. They are indications 3-1, 3-2, 3-8, 3-9, 3-11, 3-12, and 3-25.

Subsurface Indications Unacceptable to Section XI, Table IWB-3511-1 Table A-2 lists 11 subsurface indications unacceptable to Section XI requirements. Indications 2-1 and 2-2 were not reported during the preliminary preservice inspection. However, official examination data, characterizing the indications as unacceptable, were provided previously in Table A-5 of reference (a). Their status has not changed.

Indications 2-3 and 2-4 were removed in a steam generator weld core sample prior to hydrostatic testing. Therefore, they are no longer a concern. The remaining indications (2-5 through 2-11) were identified as unacceptable during the preliminary inspection and were later re-examined during the official inspection. The re-examination data is essentially the same as the preliminary inspection data. These indications remain unacceptable.

Reference (a) (Table A-2) lists 2 additional subsurface indications in pressurizer welds. These indications were identified as unacceptable to Section XI during the preliminary preservice inspection. One indication is located in a circumferential weld and the other was found in a longi-tudinal weld. Both indications were re-examined during the official inspection. Based on the re-examination data, the indications were characterized as cladding backscatter similar to the surface indication discussed above. Therefore, the indications are not reportable per Section XI requirements and are now listed as acceptable in Table A-3 of this report. They are indications 3-24 and 3-26.

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Indications Acceptable to Section XI, Table IWB-3511-1 Table A-3 lists 26 indications acceptable to Section XI requirements.

Several'of these indications have been previously discussed since they were characterized as unacceptable during the preliminary inspection.

All other indications in Table A-3 were originally reported as acceptable to Section XI for one of the following reasons:

1. indication was confirmed as I.D. surface geometry through visual inspection;

2. indication was removed by grinding with other unacceptable indications;

3. ultrasonic amplitude of the indication less than 50% DAC (Distance-Amplitude Curve);

4. a/t ratio of the indication was acceptable to Section XI Table IWB-3511-1.

These indications sere re-examined during the official inspection. The re-examination results support the preliminary disposition of these indications. Therefore, they remain acceptable to Section XI.

Conclusion After completion of the official preservice inspection of the Byron Unit 2 steam generators and pressurizer, 12 indications in component welds remain unacceptable to Section XI requirements. Supplemental examinations, weld sampling and metallurgical analyses performed prior to the official inspection identified the indication sources as very small, innocuous slag inclusions. Such inclusions are expected to have an insignificant affect on vessel weld integrity. Due to the location of the indications, their removal and subsequent weld repair involves potential significant risk to vessel-integrity. As a result, Commonwealth Edison does not intend to remove the 12 indications per Section XI preservice inspection requirements.

Fracture mechanics analyses of the Byron Unit 2 steam generators and pressurizer have been performed. The 12 unacceptable indications have been plotted on flew evaluation handbook charts developed from the fracture mechanics analyses. The handbook charts identify the critical flew sizes for each weld. These charts are provided in Attachment B. The following table identifies the charts on which each indication is plotted.

s Indication Surface Flaw Embedded Flaw Hydro Test Leak Test Number Evaluation Evaluation Temperature Temperature 1-1 A-3.2 N/A A-3.3 A-3.4 1-6 A-3.2 N/A A-3.3 A.3.4 1-9 A-4.2 N/A A-4.4 A-4.5 2-1 N/A A-3.5 A-3.6 A-3.7 2-2 N/A A-3.5 A-3.6 A-3.7 2-5 N/A A-5.5 A-5.6 A-5.7 2-6 N/A A-6.8 A-6.9 A-6.ll 2-7 N/A A-6.8 A-6.9 A-6.11 2-8 N/A A-6.8 A-6.9 A-6.11 2-9 N/A A-3.5 A-3.6 A-3.7 2-10 N/A A-7.5 A-7.6 A-7.7 2-11 N/A A-10.5 A-10.6 A-10.6 The surface flaw evaluation charts show the indications plotted as a/t versus a/1. The subsurface flaw evaluation charts show the indications plotted as a/t versus (/t. The indications that fall below the heavy line are considered subsurface indications.

Test temperature determination charts are also providad in Attachment B. These charts show the indications plotted as a/t versus //t. The location of the plotted points in relation to the temperature lines shows the minimum temperature for safe conduct of hydrostatic and leak testing.

The flaw evaluation handbook charts demonstrate that the 12 unacceptable indications fall below the 40-year critical flaw size. This means that, if the indications are assumed to be flaws of the reported sizes, they will not grow to critical sizes during the life of the plant. Per the requirements of Section XI paragraph IWB-3600, repair of the components would not be necessary if the indications were identified during an inservice inspection.

P -

A description of the steam generator fracture mechanics analysis was provided previously in reference (a). A more detailed description of the analyses for the steam generators and pressurizer is provided in Westinghouse reports WCAP-11063 and WCAP-11064. These reports address concerns of the Nuclear Regulatory Commission which were discussed in a conference call with Commonwealth Edison on February 25, 1986. The reports are enclosed as Attachment C.

To ensure that the 12 unacceptable indications do not grow to critical sizes during plant operation, augmented inservice inspections of the indications will be performed. These inspections will be conducted to the requirements of section XI, paragraph IWB-2420 for the pressurizer (class 1) weld indication and to paragraph IWC-2420 for the steam generator (Class 2) weld indications.

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ATTACISBNT A LIST OF CONTENTS

- Table A-1 Surface Indications Exceeding The Requirements Of ASME Section XI, Table IWB-3511-1

- Table A-2 Subsurface Indications Exceeding The Requirements Of ASME Section XI, Table IWB-3511-1

- Table A-3 Indications Acceptable To The Requirements Of ASME Section XI 1700K d 9

OFFICIAL PRESERVICE INSPECTION (PSI) RESULTS FOR TE SYRON UNIT 2 STEAM GENERATORS ANO PRES 9URIZER S M WELDS ,

TABLE A-1 SURFACE INDICATIONS EXCEEDING THE REQUIREMENTS OF AGME SECTION XI, TABLE IW8-3511-1 .

Walt Distance Thru Weld Thickness Length From I.D. Wall

_Ng2 gpeggngg) }ggg j,pg3_og _ (t") _ _ (_1") _ _J e *L _jd") _30_ _gd_ [ m t3 224 5/8 CCW 3.2 0.70 0.01 0.14 0.21 4.7% 60 degree scan shameed 1-1* 2095 SGC-02 2.8% thru wall. (Preliminarily reported as 7.8%) 4.0 0.75 0.02 0.43 0.60 11.2% Removed by grinding 1-2 2095 SOC-06 110 1/2 CW 8/85 0.05 0.37 0.42 12.4% Removed by Grinding 1-3 2096 SOC-05 212 3/4 CW 3.4 1.0 6/85 4.0 0.75 0 0.24 0.32 6.0% Removed by Grinding 1-4 2096 SGC-06 229 CW 8/95 0 0.24 0.27 7.3% Core sample removed 1-5 2097 SGC-02 107 1/4 CW 3.3 0.88 6/95 0 0.36 0.60 10.9% Preliminarily reported 1-6* 2097 SOC-02 219 1/4 CW 3.4 0.75 as 11.2% 42 1/2 CCW 4.0 1.0 0 0.33 0.33 8.3% Removed by Grinding 1-7 2097 SGC-06 8/85 4.0 3.5 0 0.45 0.13 11.3% Removed by Grinding 1-8 2097 SOC-06 139 1/4 CW 6/05 3.2 0.5 0 0.31 0.61 7.8% Pret teinarily reported 1-9* 2097 SON-02 11 1/4 CW as 9.7%. 4.3 3.25 0 0.51 0.16 12.8% Removed by grinding 1-10 2098 SOC-06 40 5/8 CCW 6/05 o Plotted on flaae handbook charts. 1

OFFICIAL PRESERVICE INSPECTION (PSII RESULTS F3R THE BYitON UNIT 2 CTEAM GENERATORS AND PRESSURIZER SHELL WELDS TABLE A-2 SUBSURFACE INDICATIONS EXCEEDING THE REQUIREMENTS OF ASME SE:: TION XI. TABLE IWB-3511-1 . Walt Distance Thru , Weld Thickness Length From I.D. Wall .Nes G9=eecsc5 Stee Less1190 15:1. 11"1- 1s *1. _ (d*' -* !1- - =/5- C9mments. - SGC-02 91 1/2 CW 3.2 0.75 1.97 0.235 0.16 3.8% Not reported during 2-1* 2095 the preliminary

• examination.

SGC-02 94 CW 3.2 0.6 1.50 0.41 0.34 6.4% Not reported during 2-2* 2095 the preliminary examination. 2095 SGC-02 109 1/2 CCW 3.2 0.5 1.1 0.31 0.31 4.9% Removed with core 2-3 sample at 110" CCW (see next itsal SGC-02 110 CCW 3.2 0.80 0.16 0.53 0.30 8.3% Core sample removed. 2-0 2095 GGC-03 20 $/8 CW 3.1 0.98 0.90 0.40 0.23 6.5% Preliminarily reported 2-5 e 2096 as 6.7% SCG-05 127 CW 3,4 0.80 0.90 0.60 0.34 8.8% Preliminarily reported 2-ce 2096 as B.4% SGC-05 82 CW 3.2 0.75 0.11 0.22 0.15 3.4% Preliminari!y reported 2-7* 2097 as 3.3% 2097 SGC-C5 49 3/4 CW 3.2 0.98 0.26 0.26 0.15 4.1% Preliminarily reported 2-ee as 4.1% 2090 SGC-02 to 3/4 CCW 3.2 0.70 0.26 0.26 0.19 4.0% Preliminari!y reported 2-7s as 4.1% 2090 SGC-06 134 3/4 CW 4.0 0.70 1.94 0.325 0.23 4.0% Marginally exceeds 2-10* acceptance criteria of 3.9%. (Preliminar11y reported as a.4%). 142 CW 4.0 1.00 0.40 0.64 0.32 8.0% Preliminarily 2-11e Press PC-04 1741 reported as 8.4%. O Plotted on flaw handbook charts.

                                     . OFFICIAL PRESERVICE INEiPECTION (PSI) RESULT 3 FOR TDE BYRON UNIT 2 CTEAM GENERATORS AND PRESSURIZER SHELL WELDS TABLE A-3 INDICATIONS ACCEPTABLE TO THE REDUIREMENTS OF ASME SECTION XI (PROVIDED FpR INFORMATION ONLY)                                             .

Walt Distance Thru Wald Thickness Length From I.D. Wall t!as . Geesmet titte Loc _sti_m _it"8 (L"8 (*"8 (d") _t/1 alt _ Get_s 3-1 2095 SGC-05 SG CW - Confirmed as I.D. geometry by visual examination. 3-2 2095 SGC-05 48 CW - Confirmed as I.D. geometry by visual exam,ination. - 3-3 2095 SGC-02 109 1/4 CCW - Not reportable. (Detected < 50 % DAC maximum amplitudel - 3-0 2095 SGC-02 131 1/4 CCW - Spot indication.(Detected as 52 % DAC maw. amp 1. with no measureable depth) - 3-5 2096 SGC-03 36 3/4 CW - Not reportable. (Detected < 50 % DAC monimum amplitude) -- 3-0 2096 SGC-06 54 7/B CCW - Confirmed as I.D. geometry by visual owamination. - 3-7 2096 SGC-08 132 1/4 CW -- Not reportable. (Detected < 50 % DAC maximum amplitude) 3-8 2096 SGC-05 190 3/4 CW - Confirmed as I.D. geometry by visual examination. -- 3-9 2097 SGC-01 207 3/B CW - Confirmed as I.D. geometry by visual examination. - > 3-10 2097 SGC-02 217 CW - Repeat of indication at 219 1/4 CW. (See Table A-1) 3-11 2097 90C-05 40 1/4 CCW - Confirmed as I.D. geometry by visual awamination. -- 3-12 2097 SGC-05 45 1/2 CCW - Confirmed as I.D. geometry by visual examination. - 3-13 2097 SGC-06 43 CCW -- Removed by grinding with indication at 42 1/2 CCW. (See Table A-1) - 3-14 2097 SGC-06 44 1/2 CCW -- Confirmed as I.D. geometry by visual examination. -- h

TABLE A-3 - (CONTINUED) - Walt Distance Thru

• Weld Thickness Length

_j a " t_ _J1"L From 1.D. _jrL Wall _jen _s!L _s/1_ Cges,ess ', t% Cgmegeret pra, Less119e SGC-06 115 7/8 CCW - Confirmed as I.D. geometry by visual examination. -- 3-15 2097 2097 SGC-06 118 1/2 CCW - Confirmed as I.D. geometry by visual examination. -- 3-16 ~ 3-17 2099 SGC-02 11 1/8 CCW - Repeat of indication at 10 3/4 CCW. (See Table A-21 - 11 7/B CCW 3.2 0.4 - O.26 0.20 0.25 3.1% Allowable a/t = 4.1% 3-1B 2099 SGC-02 3-19 2099 SGC-06 40 CCW - Removed by grinding with indication at 40 5/9 CCW. (See Table A-1) 3-20 2099 SGC-06 132 1/4 CW - Not reportable. (Detected < 50 % DAC maximum amplitudel -- SGC-06 129 CW 4.0 0.5 1.96 0.26 0.26 3.2% Allowable a/t = 4.2%. 3-21 2098 This data from the preliminary exam. Confirmed as not reportable during official PSI. 3-22 2099 SGC-03 39 1/2 CCW 3.2 0.5 0.27 0.26 0.26 4.1% Allowable a/t = 4.2%. This data from the preliminary exam. Confirmed as not reportable during official PSI. 3-23 Press PL-01 7" to 17" - Not reportable. (Detected < 50 % DAC maximum amplitude) - 1741 below PC-02 3-24 Press PL-02 15 5/8" - Evaluated as originating f rom metallurgical structure at the clad / base 1741 from PC-02 metal interface. Indication is approximately 1 1/2" f rom weld centerline.- 3-25 Press PC-03 75 1/2 CW - Evaluated as originating from metallurgical structure at the clad / base 1741 metal interface. Indication is approximately 1 1/2" from weld centerline.-- 3-26 Press PC-04 5 1/4 CW - Evaluated as originating f rom metallurgical structure at the clad / base 1741 metal interface. Indication is approximately 3/8" from weld centerline.-- 5 g. t}}