ML20197E826
| ML20197E826 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 05/09/1986 |
| From: | Ainger K COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 1676K, 86-04, 86-4, NUDOCS 8605150324 | |
| Download: ML20197E826 (7) | |
Text
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Commonwealth Edison O
C ) One First Nitionti Plata, Cluctgo. Ilhnois O
Addrsss Riply to: Post Office Box 767 Chicago, Illinois 60690 May 9, 1986 a
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Mr. James G. Keppler Regional Administrator l
U.S. Nuclear Regulatory Conunission i
Region III
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799 Roosevelt Road l
1 Glen Ellyn, IL. 60137 i
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Subject:
Byron Station Unit 2 t
10CFR50.55(e) Report No. 86-04 Rejectable Indications Identified During Preservice Inspection of Steam Generators f
and Pressurizer NRC Docket No. 50-455
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Reference (a): October 11, 1985 letter from K.A. Ainger to H.R. Denton i
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Dear Mr. Keppler:
On April 9, 1986, the Comunonwealth Edison Company Project Engineering Department notified Mr. R. Lerch of your office of a deficiency reportable pursuant to 10CFR50.55(e) regarding twenty-one (21) rejectable weld indications identified during the Unit 2 Preservice Inspection at Byron Station. This letter fulfills the thirty (30) day reporting requirement and i
is considered a final report. For tracking purpose, this deficiency was j
assigned number 86-04.
Description of Deficiency 1
Preliminary preservice inspection examinations, performed prior to i
system hydrostatic testing, identified 45 ultrasonic indications in welds of 4
the Byron Unit 2 steam generators and pressuriser. Eight (8) of these indications were removed from the welds by grinding. Three (3) indications l
were removed by core sampling.
Supplemental non-destructive examinations and metallurgical' analysis of the weld samples were subsequently performed to determine the nature, cause and actual sizes of the indications. Visual inspections of weld inner i
diameter surfaces identified the source of ten (10) indications as surface J
geometry. Analysis of the weld samples verified that the remaining weld ~
indications are small slag inclusions formed during the fabrication process.
8605150324 860509 gon noocxOS45f M12 M j
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Mr. J.C. Keppler 2-May 9, 1986 i
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h slag inclusions are located between weld pass interfaces. h analysis also demonstrated that ultrasonic examination techniques exaggerated the length and through-wall dimensions of the indications by at least a factor of two.
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1 Hydrostatic testing and the official preservice Inspection of the Byron Unit 2 steam generators and pressurizer were then completed. N official inspection was performed to the requirements of ASME Section II 1977 i
4 Edition with addenda through Summer 1978 Addenda. Two additional indications
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i were identified in a steam generator weld during the official inspection.
These indications were characterized as unacceptable to Section II i
requirements. Previously identified indications were re-examined with ultrasonic techniques. h se reexaminations identified ten (10) indications as unacceptable.
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The twelve (12) indications-identified as unacceptable during the j
official Preservice Inspection and the nine (9) indications removed from the welds were reported to Region III on April 9, 1986. All but one indication j
are located in steam generator welds. The disposition of all 47 indications are provided in the attached tables.
Analysis of Safety Implications 4
Stresses due to system pressure and repeated heat-ups and cooldowns have the potential for causing Code rejectable weld indications to propagate into through-wall cracks. There is a possibility that such propagation might occur before it could be detected by nondestructive testing during the first inservice inspection interval.
j For the indications in the pressurizer, a through-wall crack would result in reactor coolant system (RCS) leakage. In such an event, the loss of
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RCS inventory is expected to be small and would be detected by the various available reactor coolant inventory monitoring systems.
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For the indications in the steam generators, a through-wall crack would result in a secondary system steam leak. If such a leak occurred, the j
leak would be expected to be small and it would be detected by a change in the
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containment environmental parameters as well as a change in the containment sump inventory.
l In both cases of weld indication propagation, the resultant leaks are
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expected to be promptly detected in order to prevent any adverse safety consequences.
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l Mr. J.G. Keppler May 9, 1986 4
n Corrective Action The twelve (12) unacceptable indications have been characterized as very small innocuous slag inclusions based on ultrasonic test data, analysis of weld samples, and information gained during grinding.
Since the small slag j
inclusions are expected to have little affect on vessel weld integrity,~ the present condition of the components will not reduce the level of plant j
safety. The integrity of the vessels can be best preserved by not removing I
the indications. Fracture mechanics analyses have been performed which accept the indications in the component welds for the forty (40) year plant life.
j The preliminary preservice inspection data, details of visual examinations, weld sampling and grinding, and preliminary fracture mechanics 3
i were submitted to NRR in reference (a).. The official inspection results and i
final fracture mechanics analyses will be submitted in the near future.
Relief from repair requirements will be requested for the twelve (12) i unacceptable indications.
i Our disposition of the indications has been discussed previously with l
NRR.
Relief from further repairs is expected after their review of the final fracture mechanics analyses. Since the approval should be given shortly, this j
letter is considered a Final Report.
l Please address any questions that you or your staff may have 4
concerning this matter to this office.
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j Very truly yours,
.i i,
l K.sA. Ainger i
Nuclear Licensing Administrator j
Attachments j
cc: Byron Resident Inspector Director of Inspection and Enforcement U.S. Nuclear Regulatory Commission
' Washington, D.C. 20555 1676K i
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i DFFICIAL PRESERVICE INSPECTION (PSI) RESULTS FOR THE BYRON UNIT 2 STEAM GENERATORS AND PRESSURIZER SHELL WELD 3 TABLE IWB-3511-1 TABLE A-1 SURFACE INDICATIONS EXCEEDING THE REOUIRENENTS OF ASME SECTION XI, Walt Distance Thru Weld Thickness Length From I.D.
Wall Ng, Cgeoggggg ggee Lgengigo
_15:1_
_11:1_
_1s:1_
_1d:1_
_st1_
_stg_
Cgegeogy_
1-10 2095 SGC-02 224 5/8 CCW 3.2 0.70 0.01 0.14 0.21 4.7%
60 degree scan showed 2.8% thru wall.-
(Preliminarily reported as 7.8%)
i 1-2 2095 SGC-06 110 1/2 CW 4.0 0.75 0.02 0.43 0.60 11.2%
Removed by grinding 8/85 1-3 2096 SGC-05 212 3/4 CW 3.4 1.0 0.05 0.37 0.42 12.4%
Removed by Grinding 6/85 I
1-4 2096 SGC-06 229 CW 4.0 0.75 0
0.24 0.32 6.0%
Removed by Grinding 8/85 1-5 2097 SGC-02 107 1/4 CW 3.3 0.88 O
O.24 0.27 7.3%
Core sample removed 6/85
?
1-60 2097 SGC-02 219 1/4 CW 3.4 0.75 0
0.36 0.60 10.9%
Preliminar11y reported as 11.2%
i 1-7 2097 SGC-06 42 1/2 CCW 4.0 1.0 0
0.33 0.33 8.3%
Removed by Brinding 8/95 1-0 2097 SGC-06 139 1/4 CW 4.0 3.5 0
0.45 0.13 11.3%
Removed by Grinding 6/05 1-93 2097 SON-02 11 1/4 CW 3.2 0.5 0
0.31 0.61 7.8%
Preliminarily reported as 9.7%.
i 1-10 2098 BGC-06 40 5/8 CCW 4.3 3.25 0
0.51 0.16 12.8%
Removed by grinding 6/95 j
O Plotted on flaw handbook charts.
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DFFICIAL PRESERVICE INSPECTION (PSI) RESULTS FOR THE CYRON UNIT 2 STEAM GENERATORS AND PRESSURIZER SHELL WELDS TABLE A-2 SUBSURFACE INDICATIONS EXCEEDING THE REQUIREMENTS OF ASME SECTION XI, TABLE IWD-3511-1 Walt Distance Thru Weld Thickness Length From I.D.
Wall Nez Ceme90so%
Dste Lesat190 it "1-11"1-J s "l-19"1-ell-el%-
Ceessots-f2-to 2095 SGC-02 91 1/2 CW 3.2 0.75 1.97 0.235 0.16 3.0%
Not reported during the preliminary examination.
2-20 2095 SGC-02 94 CW 3.'z O.6 1.50 0.41 0.34 6.4%
Not reported during the preliminary examination.
- 2-3 2095 SGC-02 100 1/2 CCW 3.2 0.5 1.1 0.31 0.31 4.0%
Removed with core sample at 110" CCW (see next item)
- 2-4 2095 SGC-02 110 CCW 3.2 0.08 0.16 0.53 0.30 0.3%
Core sample removed.
!2-5 e 2096 SGC-03 20 5/8 CW 3.1 0.00 0.80 0.40 0.23 6.5%
Preliminarily reported as 6.7%
i2-64 2096 SCO-05 127 CW 3.4 0.00 0.90 0.60 0.34 8.8%
Preliminarii;Teported as 0.4%
2-70 2097 SGC-05 82 CW 3.2 0.75 0.11 0.22 0.15 3.4%
Preliminarily reported as 3.3%
,2-02 2097 SGC-05 49 3/4 CW 3.2 0.88 0.26 0.26 0.15 4.1%
Preliminarily reported as 4.1%
O.26 0.26 0.19 4.0%
Preliminarily reported l
2-93 2090 SGC-02 to 3/4 CCW 3.2 0.70 as 4.1%
4 2-103 2098 SGC-06 134 3/4 CW 4.0 0.70 1.94 0.325 0.23 4.0%
Marginally exceeds f
acceptance criteria of 3.9%.
(Preliminarily reported as 4.4%).
2-11e Press PC-04 142 CW 4.0 1.00 0.40 0.64 0.32 0.0%
Preliminar11y reported as 8.4%.
1741 o Plotted on flaw handbook charts.
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. 0FFICIAL PRESERVICE INSPECTION (PSI) RESULTS FOR THE BYRON UNIT 2 STEAN GENERATORS AND PRESSURIZER SHELL WELDS TABLE A-3 INDICATIONS ACCEPTABLE TO THE REQUIREHENTS OF ASNE SECTION XI (PROVIDED FOR INFORMATION ONLY)
Walt Distance Thru Weld Thickness Length From 1.D.
Wa!!
Ngt gogggngn(
Segg Locgt(gn
_it;L_
_i(1L_
_ig"L_
_id"L_
_qfL_
_qLt_
Ggementg_____
3-1 2095 SGC-05 OO CW
-- Confirmed as I.D. geometry by visual examination.
3-2 2095 SGC-05 48 CW
-- Confirmed as I.D. geometry by visual examination.
3-3 2095 SGC-02 109 1/4 CCW
-- Not reportable. ??'tected < 50 % DAC maximum amplitude) 3-4 2095 SGC-02 131 1/4 CCW
-- Spot indication.(Detected as 52 % DAC max. ampI. with no measureable depth) --
3-5 2096 SGC-03 36 3/4 CW
-- Not reportable. (Detected < 50 % DAC maximum amplitude) 3-6 2096 SGC-06 54 7/D CCW
-- Confirmed as I.D. geometry by visual examination.
3-7 2096 SGC-OB 132 1/4 CW
-- Not reportable. (Detected < 50 % DAC maximum amplitude) 3-0 2096 SGC-05 190 3/4 CW
-- Confirmed as I.D. geometry by visual examination.
3-9 2097 SGC-01 207 3/8 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 SGC-05 40 1/4 CCW
-- Confirmed as I.D. geometry by visual examination.
7 3-12 2097 SGC-05 45 1/2 CCW
-- Confirmed as I.D. geometry by visual examination.
-- Removed by grinding with indication at 42 1/2 CCW. (See Table A-1) 3-13 2097 SGC-06 43 CCW 3-14 2097 SGC-06 44 1/2 CCW
-- Confirmed as I.D. geometry by visual examination.
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TABLE A-3 (CONTINUED)
Walt Distance Thru Weld Thickness Length From I.D.
Wall U91 C9?D9D9Dt 99^2 L95^%A9D 11"E-ll "l-19"l-jd_"J_
_af]_
_pft_
Cggggg%s_
3-15 2097 SGC-06 115 7/8 CCW
-- Confirmed as I.D. geometry by visual examination.
3-16 2097 SGC-06 110 1/2 CCW
-- Confirmed as I.D. geometry by visual examination.
3-17 2090 SGC-02 11 1/8 CCW
-- Repeat of indication at 10 3/4 CCW. (See Table A-2) 3-10 2090 SGC-02 11 7/8 CCW 3.2 0.4 0.26 0.20 0.25 3.1%
Allowable a/t = 4.1%
-- Removed by grinding with indication at 40 5/8 CCW. (See Table A-1) 3-19 2090 SGC-06 40 CCW 3-20 2098 SGC-06 132 1/4 CW
-- Not reportable. (Detected < 50 % DAC maximum amplitude) 3-21 2098 SGC-06 129 CW 4.0 0.5 1.96 0.26 0.26 3.2%
Allowable a/t = 4.2%.
This data from the preliminary exam.
Confirmed as not reportable during official PSI.
3-22 2090 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 belew PC-02 3-24 Press PL-02 15 5/B"
-- Evaluated as originating from metallurgical structure at the clad / base 1741 from PC-02 metal interface. Indication as approximately 1 1/2" from weld centerline.--
3-25 Press PC-03 75 1/2 CW
-- Evaluated as originating from metallurgical structure at the clad / base metal interface. Indication is approMimately 1 1/2" from weld centerline.--
1741 3-26 Press PC-04 5 1/4 CW
-- Evaluated as originating from metallurgical structure at the clad / base metal interface. Indication is approximately 3/0" from weld centerline.--
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