ML20135E377
| ML20135E377 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 11/30/1996 |
| From: | Maurice Heath, Keck R, Miller W GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20135E361 | List: |
| References | |
| NUDOCS 9612110213 | |
| Download: ML20135E377 (7) | |
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1 Attachment I to JPN-96-052 j
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General Electric Nuclear Energy Report
, " Evaluation of Ultrasonic Indications in RPV Closure Head Weld i
VC-TH-1-2 at the James A. FitzPatrick Nuclear Power Plant"
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i l November 1996 I
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New York Power Authority James A. FitzPatrick Nuclear Power Plant Docket No. 50-333 9612110213 961205 PDR ADOCK 05000333 G PDR
GENuc/earEnergy l
12200 lierbert II'mne Court, Suite 100. fluntersville. NC 280~8 l_
November 19%
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, 1 f Evaluation of Ultrasonic Indications in RPV x, g} f Closure Head Weld VC-TH-1-2 at the gn James A. Fitzpatrick Nuclear Power Plant g ,g Q @n0 l3 a
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h Prepared by: pf w- pii~~ "dM, /
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gg l G zer3 E 4 Wade P. Miller. GE-NE in pection Senices, Senior NDE Specialist Reviewed by: <pf j g'r_TV/' /_ _ / I >
Michael A. Heath. GE NE Inspection Services,i.evel til Approved by:
hard L. Ke ObNE Inspection Senices, Project Manager Reviewed by:
! Aturo Smi[New York Power Authonty,lSI Project Manager Review ed by: //
'New York Pder'kuthority. Quality Assurance i
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24 Evaluation of Ultrasonic Indications In RPV Closure llead Weld VC-Til-1-2 at the James A. Fitzpatrick Nuclear Power .
Plant l
TABLE OF CONTENTS Description Pane i Hackground..................................................................................................................3 1996 E x a m i n a t i o n Res u l ts............................................................................................ 3 Review of Previous UT Exa mina tion Results.............................................................. 4 i
PSIResults....................................................................................................................4 f ISI Results (1990, 199 2, & 1995 )................................ ................................................. 4 Co m pa rison of Era m i n a tion Res ul t s ........................................................................... 5 Conclusions...................................................................................................................5 1
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3 Evaluation of Ultrasonic Indications In RPV Closure Head )
Weld VC-TH-1-2 at the James A. Fitzpatrick Nuclear Power ;
Plant l
l Backeround l l
Ultrasonic (UT) examinations of RPV Closure Head weld VC-TH-1-2 during the 1990 refueling outage, revealed indications that exceeded the ASME Section XI allowable flaw sizes when the provisions of USNRC Regulatory Guide 1.150 were considered. The UT was performed in accordance wit h the requirements of ASME Section XI,1980 Edition with Addenda through Winter 1981. The data was evaluated in accordance with ASME Section XI as modified by Reg. Guide 1.150 requirements. Sevemt indications were detected with two areas containing flaw s that exceeded the allowable flaw size. These areas wcre identified as Area 1 and Area 2. The purpose of this report is to resolve the indications located in Areas 1 and 2. The remaining indications w cre found to be acceptable.
- The UT data, for both Area 1 and Area 2. indicated a slightly subsurface flaw s with small through wall I
! dimensions. Characterization of the indications was performed using both refracted longitudinal wave (RL) and vertically polarized shear wave (SV) techniques. In addition, both magnetic panicle (MT) and l radiographic (RT) techniques u ere used to supplement the UT data. The supplemental MT confirmed l l that the indications were subsurface. since no MT indications wcre detected in the area of the UT indications. The supplemental RT showed w clding flaws in the area of the UT indications.
Area 2 contained two flaw s in close proximity. The flaws w cre analyzed as two unacceptable subsurface j i planar flaws. It was decided that even though the flaw s could be shown to be separated. they would be !
combined and treated as a single surface flaw for the purpose of a Fracture Mechanics evaluation.
Combining the flaws created a bounding flaw size for both Area I and Area 2. Treating the combination as surface connected3ielded a very conservative structural evaluation. The analy sis show ed that the flaws did not reduce the structural margin below the Section XI allowable and that the plant was ;
operable "as is." i The fracture analysis and use as is disposition was accepted by the USNRC with the stipulation that the I w cid must be monitored for flaw growth during the next three operating cycles. The monitoring was performed during the 1992.1995, and 1996 refueling outages. Minor differences in exam data w cre noted when comparing the three re-examinations. The difTerences are attributable to several factors. The major differences are due to treating the flaws individually, rather than combining them to develop a l bounding flaw size. Over the six 3 car period of monitoring these flaws. there has been no detectable change in the sizes. This indicates that they are stable.
The remainder of this report documents the comparison of inspection data performed during evaluation of the previously recorded flaw s.
1996 Examination Results Areas I and 2 contained the indications that required monitoring. These areas were reexamined during the 19% refueling outage. The reexamination confirmed the presence of the two low amplitude reflectors detected in 1990. The examination data is contained in Data Package R-022. The areas examined and the results for each were as follows:
Area 1, beginning at 24" and extending to 25" CCW from Meridional Weld VV-TH-1E. This i area contained an indication from 24.0" to 25.0". This location is consistent with the initial and subsequent reexaminations of the indication. There wcre no significant changes in location, amplitude, or through wall depth of the indication.
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'm p l 4V Evaluation of Ultrasonic Indications In RPV Closure ficad Weld VC-TH-1-2 at the James A. Fitzpatrick Nuclear Power Plant Area 2, beginning at 57" and extending to 62" CW from Meridional Weld VV-TH-lE. This area contained an indication from 55.8" 61.0". This location is consistent with the initial and i
! subsequent reexaminations of the indication. There w cre no significant changes in location.
amplitude, or through wall depth of the indication. j The 19% UT data shows no evidence of changes in these flaws over the previous operating cycle. The ?
l minor differences in flaw length data are attributed to measurement error inherent in locating a point on a !
l spherical surface. There was no change in the through wall dimension of the flaws. The predicted i j growth of these flaws should have been s 0.300" based on the original fracture mechanics analysis.
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l Review of Previous UT Examination Results l l
1 PSI Results j The Preservice inspection was performed in 1974. This required use of an early Edition of the ISI Code.
No indications u ere detected on Weld VC-TH-1-2. Changes in equipment and examination techniques.
for example implementation of USNRC Regulatory Guide 1.150. negate the possibility of direct comparison betw een the PSI and subsequent ISI exams. He PSI data was not used during evaluation of these indications.
ISI Results (1990,1992, & 1995) l 1990 ISI l The indications in Areas 1 and 2 were first detected during the 1990 ISI. They were evaluated as subsurface planar flaws in accordance with Reg. Guide 1.150 criteria. There was no ASME Section XI evaluation. since flaw amplitude did not exceed 100% DAC. Using the location and amplitude criteria of the Reg. Guide, the flaws exceeded the Table IWB-3510-1 allowable flaw sizes.
During the im estigation of these indications the origin of the indications in Area 2 was determined to be flaw s in a w cid build-up. He w cid was radiographed on site and a slag inclusion was evident. The
! fabrication radiographs wcre compared to the site radiographs. The same inclusion was seen on both sets l
of radiographs. He radiographs w ere digitized and enhanced during the evaluation process. The enhanced images accurately defined the inclusion as slag.
NYPA decided to treat these flaws in a conservath e manner. A fracture mechanics analysis of the bounding flaw size was performed. The flaw was treated as surface connected. This yields a result that considers flaw growth due to environmental effects. His analysis predicted a growth rate. from combined environmental and fatigue factors, of 0.096" for the upcoming 18 month fuel cycle. A change in through wall depth, on the order 0.100", would be sufTicient to be detected during reexaminations of these flaws.
1992 ISI Areas 1 and 2 were reexamined during the 1992 refueling outage. There were no significant changes in flaw dimensions. He locations of the flaws uere permanently marked. This enabled the relook locations to be reproduced accurately. He examinations w cre performed using equipment and techniques similar to those used in 1990. NYPA performed the comparison of 1990 and 1992 examination data. NYPA determined that there were no significant changes in the flaws.
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5 Evaluation Of Ultrasonic Indicati0ns In RPV C10sure llead Weld VC-Til-1-2 at the James A. Fitzpatrick Nudear Power
, Plant i
1995 ISI Arcas 1 and 2 w cre reexamined during the 1995 refueling outage. The reexamination conEnned that there were no changes in flaw dimensions. The flaws wcre evaluated as stable-Comparison of Examination Results Comparison of the data gathered. for Weld VC-TH-1-2. from 1990 through 1996. show s that there has been no significant change in any flaw parameter. The flaw s w cre determined to be slag inclusions.
Investigation show ed that there is a w cid build-up on the head side plates. The slag is contained within this build-up.
Comparison Of Examination Results @ 20% DAC
. Year ind. "a* "l* s/l att% Remarks Examined #
1990 #1 0.350* 2.3 n" .15 8.8 Initial Detection, Benchmark Sire
- 2 0.166* 5.00* .03 4.2 Initial Detection, Benchmark Size 1992 #1 0.000* 1.00* .05 1.3
- Change, in plotting method
- 2 0.400* 5.50' .07 9.5
- Change, "a* includes ligament 1995 #1 0.050* 1.00* .05 1.3
- Change, in plotting method
- 2 0.400* 5.50- .07 9.5
- Change, "a* includes ligament 1996 #1 0.197* 1.00* .19 4.9 No Change, plotted without beamspread
- 2 0.200* 5.20' .03 5.0 No Significant Change, ligament deducted
- The differences in recorded dimensions of Flaw #1 and Flaw #2are due to differences in locatirg the areas and data plotting. There is no evidence of any change in actual flaw dimensions.
The areas containing the indications have been examined during three consecutive refueling outages; since their discovery. The reexaminations used equipment and techniques that w cre similar to that used during the initial examination. The data w as evaluated to the same criteria as that used in 1990. There was no significant change in flaw size detected during the three reexaminations. All data was within the measurement error of the manual UT techniques used..
Conclusions The flaws discovered in Weld VC-TH-1-2. during the 1990 refueling outage have exhibited no evidence of growth after three additional cycles of operation. The Fracture Mechanics evaluation performed in 1990 show ed an expected flaw growth of 2 0.300" if these w ere indeed surface connected flaw s. The lack of detectable flaw growth, over three operating cy cles. confirms the flaw s are subsurface.
Both Area 1 and Area 2 have been shown to contain fabrication flaws that wcre acceptable at the time of manufacture and were documented in the records (radiographs. etc.). As such the flaw s are acceptable for the life of the plant unless they show growth. They have been stable since fabrication of the Top licad in 1969 and are expected to remain so throughout the remaining plant life.
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6 Evaluation of Ultrasonic Indications In RPV Closure llead ;
l Weld VC-Til-1-2 at the James A. Fitzpatrick Nuclear Power '
Plant After evaluation of the original inspection data and three subsequent reexaminations of the flaw ed areas, it is recommended that Weld VC-TH-1-2 be returned to the normal inspection frequency. consistent with Plant Technical Specifications.
Calculations j hul Arca 1. beginning at 24" and extending to 25" CCW from Meridional Wcld VV-TH-lE. This area contained an indication from 24.0" to 25.0". The analysis is as follow s: ,
s (distance from surface) = 0.100" If s/a (y factor) is 2.4. flaw is subsurface s/a = 0.100/0.197 ,
s/a = .51 flaw is subsurface y factor is also .51 .
2a (total through wall dimension) = 0.394* a = 0.394"/2 a = 0.197" i i
I (indication length) = 1.00" a/l (aspect ratio) =.19 t (weld thickness) = 4.00" !
alt % (indication through wall percentage) = ,197/3.86.s100 = 4.9%
alt % allowable = Table value from IWB-3510-1 = 3.ly alt % allowable = 3.2 x .51 = 1.63% !
4.9% > 1.63% Flaw exceeds the ASME XI allowable site.
l Arca 2 Area 2. beginning at 57" and extending to 62" CW from Meridional Wcld VV-TH-1E. This area contained an indication from 55.8" 61.0".. The analysis is as follows:
s (distance from surface) = 0.100" If s/a (y factor)is 2.4. flaw is subsurface s/a = 0.100/0.200 s/a = .50 flaw is subsurface y factor is also .50 2a (total through wall dimension) = 0.400" a = 0.400"/2 a = 0.200" 1 (indication length) = 5.20" a/l(aspect ratio) =.03 t (weld thickness) = 4.00" l a/t% (indication through wall percentage) = .200/3.86 x100 = 5.0%
a/t% allowable = Table value from IWB-3510-1 = 2.4y a/t% allowable = 2.4 x .50 = 1.20%
l 5.0% > 1.20% Flaw execeds the ASME XI allowable size.
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