ML20024H849
| ML20024H849 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/19/1993 |
| From: | Bamford W, Kurek D, Rishel R WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20024H848 | List: |
| References | |
| MEM-MNA-296(93), MEM-MNA-296(93)-R02, MEM-MNA-296(93)-R2, NUDOCS 9308260007 | |
| Download: ML20024H849 (16) | |
Text
_ _ _ . __ - _ _ _ _ _ _ _ _ _ -
MEM-MNA-296(93)
Rev. 2 .
! I i
EVALUATION OF THE ULTRASONIC TEST RESULTS FROM- -
THE 1993 ISI ON THE UNDERCLAD FIAW INDICATIONS LN THE SEQUOYAH UNIT 1 REACTOR VESSEL NOZZLES.
Performed by : M. d. 7 /14 / 9 3 R. D. Rishel,
) ,
Metallurgical & NDE Analysis W laf93 .
W. H. Bamford, l Structural Mechanics Technology Veri 5ed by : o7 9[es direk, // {
Metallurgical & NDE Analysis 1
)
Westinghouse Energy Systems 1 P.O. Box 355 Pittsburgh, Pennsylvania 15230 MNA-296.WPFAW93 9308260007 930818 D PDR ADDCK 05000327 !!d .
G PDR jf
Evaluation of the Ultrasonic Test Results from the 1993 ISI on the Underciad Flaw Indications in the Sequoyah Unit 1 Reactor Vessel Nozzles l
I. OBJECTIVES __.
The objectives of this effort were to evaluate the ultrasonic test results from the 1993 inservice inspection (ISI) on the underclad flaw indications in the Sequoyah Unit 1 ,
reactor vessel nozzles, and to evaluate whether there has been any change in measured sizes with respect to the 1980 supplemental preservice inspection (PSI) results.
II. SCOPE The scope of this effort is defined as follows:
(1) Evaluate the ultrasonic sizing methodology used by Southwest Research Institute (SwRI) for the ISI, and relate it to the 1980 PSI sizing methodology. r l
(2) Evaluate the indications with respect to IWB-3500 and IWB-3600 using the raw data, and discuss the stmetural integrity.
(3) Explain any changes in the indication sizes as measured in the 1980 PSI and 1993 ISI examinations.
) III. EVALUATION OF ULTRASONIC SIZING METHODOLOGY As part of the 1993 SwRI ISI program related to the Sequoyah Unit I reactor vessel nozzle underclad flaw indications it was required to compare the baseline procedures (per the 1980 supplemental PSI examinations) with current ASME Section XI/ Regulatory Guide 1.150 procedures (per the 1993 SwRI ISI examinations)*. This comparison was performed using a set of underclad cracking test blocks identified in table 1, a similar manual baseline PSI procedure as used in 1980, and an automated ASME Section XI/ Regulatory Guide 1.150 ISI examination procedure as used in 1993.
l The results of these comparisons in terms of length and depth sizing errors for cracks are indicated in tables 2 and 3, respectively. These same results are shown graphically i
in figures 1 and 2, respectively. The PSI length sizing technique is a 1/4 maximum amplitude drop method also referred to as -12dB drop. The SwRI length sizing l
technique is a 1/2 maximum amplitude drop method also referred to as -6dB drop. The data when taken as a whole indicates that the PSI technique tends to oversize such cracks (mean error = 0.23") and the SwRI technique tends to undersize such cracks I (mean error = -0.08"). However when the data is presented graphically (figure 1) it is shown that both techniques oversize small flaws, i.e. lengths less than 1", with the SwRI technique being the more accurate. (Note: The underclad flaw indications found in the Sequoyah Unit I reactor vessel nozzle bores are less than 1".) The data scatter, though, is somewhat large for the flaws less than 1" long regardless of technique. Thus the most appropriate conclusion is that und'e rclad flaws appear to be oversized in length MNA-NWPF:6/15/93 l
l
i for either technique when the true lengths are small. This is consistent with ultrasonic test experience and theory on small flaws where the ultrasonic beam is larger than the flaw size. ,
i The PSI depth sizing technique was based solely on a length to width ratio of 3:1, i.e. ,
the depth is 1/3 the length. The SwRI depth sizing technique is based on the use of the I
SLIC (Shear and Longitudinal Waves, Inspection and Characterization) transdu.cer and a methodology dependent on the recognition of time-based ultrasonic responses from crack extremities. The latter technique is more reliable than amplitude-based or constant length / depth ratio sizing methodologies. The results of the laboratory investigation are indicated in table 3 and graphically shown on figure 2. Thus the conclusion is that the SwRI technique, when it is capable of distinguishing the crack tip reflectors, is a more realistic depth measurement tool.
IV. EVALUATION OF FLAW INDICATIONS WITH RESPECT TO STRUCTURAL INTEGRITY The underclad flaw indications found in the 1980 PSI examinations and recharacterized in the 1993 ISI examinations have been plotted on the appropriate flaw evaluation charts from the Sequoyah Units 1 and 2 reactor vessel flaw evaluation handbook (WCAP 13668)2, as shown in figures 3 and 4, for both the inle and the outlet nozzle bore regions.
As seen in these figures, the indications are all below the limits of the flaw acceptancee standards of paragraph IWB-3500'(shown as curve "D" on figures 3 and 4). Therefore they are all acceptable without the need for fracture mechanics evaluation, although the
} fracture evaluations have been completed and the results are also shown in the figures.
The flaws could be much larger and still be acceptable by analysis, as easily ~seen on the figures.
V. DISCUSSION ON CHANGES IN INDICATION SIZES Table 4 shows the 1993 ISI data for each underclad flaw indication in the Sequoyah Unit I reactor vessel nozzles. Also included are the corresponding data obtained from the 1980 PSI examination." l The 1993 indication lengths are longer for the majority of the indications. However, l these results do not necessarily mean that the imderclad reflectors have grown in length.
Significant procedural differences between the 1980 PSI examinations and the 1993 ISI examinations make a direct correlation of data difficult if not unreliable. These include:
The 1980 PSI examinations were performed manually. Manual examinations are more error prone than the 1993 automated ISI examinations due to operator fatigue, operator discomfort from being in a confined space, and a variety of measurement error sources (coarser measurement devices, coarser measurement procedure, recording errors, and reading errors).
MNA-?%WPFW1193
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- The 1980 PSI examinations were performed with different ultrasonic test equipment, specifically transducers and instruments, having different characteristics even from that used in the laboratory investigations discussed ;
above.
- As observed in table 2 and figure 1, the error in measuring flaws less than 1" long l is highly variable for each technique used in the examinations. __.
l 1
Te length sizing in the 1980 PSI examinations was performed on signals having amplitudes ranging from 75 to 355% DAC, and in the 1993 ISI examinations on signals having amplitudes ranging from 6 to 67% DAC. !
l Experimental evidence exists that indicates that in the reactor vessel bore area shallow i
flaws tend to grow in length but not in depth when the vessel is subjected to relatively severe thermal shock events, but these are rare events. No experimental results are available on the behavior of these cracks under normal operational loadings. However it is our technical judgement that the underclad flaw indications will not extend in ;
length during future service under normal operational loadings. If one could postulate I 1
longer flaws at the same depth, the plotted points, in figures 3 and 4, would simply move to the left ("1" would increase, while "a" would remain the same). It is easily ;
seen from the two flaw evaluation charts that if this were to occur, all the flaws would 1 continue to be acceptable for continued service, and would most likely still be smaller than the acceptance standards ofIWB-3500.
In terms of the indication depths, the 1993 ISI measured depths should be considered more accurate than the 1980 PSI depths due to the manner in which they were determined. No correlation between the1wo sets of data can be performed.
VI. CONCLUSIONS l The following conclusions can be offered through the review of this data.
- (1) The length sizing methodology used by SwRI tends to oversize underclad crack j reflectors less than 1" long in the sample set available with a large variability. A
- similar result is obtained using a duplication of the 1980 supplemental PSI length sizing methodology. It is expected that this trend would continue in field implementation.
l (2) The depth sizing methodology used by SwRI sizes the underclad crack reflectors in the sample set more accurately than the estimated depths of the 1980 supplemental PSI methodology, and would be expected to reDect a similar type accuracy in Seld implementation.
(3) The measured 1993 ISI flaw indications satisfy the acceptance standards of the ASME Code Section XI, IWB-3500 and therefore are considered acceptable for continued service.
MNM%WPF6%93
4 (4) Correlation of underclad flaw indication sizes between the 1993 ISI and the 1980 PSI examination is difficult due to significantly inherent differences in the inspection procedures. Therefore any judgement on the increased measured lengths in the 1993 ISI examinations is not feasible.
I (5) If increased lengths are postulated assuming relatively constant depths, the flaw indications would still be acceptable for continued service. _
i V. RECOMMENDATIONS .
t The following recommendation is offered from the review of this data.
(1) The 1993 ISI results should be regarded as the new baseline for any future I comparisions since the inspection procedures are expected to more closely compare. l VI. REFERENCES
)
- 1. Facsimile Transmittal from Grady Lagleder, SwRI, to Rick Rishel, Westinghouse,
) on May 26,1993: SwRI Program on the Underclad Flaw Indications in the <
Sequoyah Unit 1 Reactor Vessel Nozzles. l
- 2. WCAP-13668 : Handbook on Flaw Evaluation for Sequoyah Units 1 and 2 Reactor Vessels, W. H. Bamford and D. E. Prager, April 1993.
- 3. ASME Code Section XI,1977 Edition including the 1978 Summer Addenda. [
) x ;
- 4. Facsimile Transmittal from David Goetcheus, TVA, to Don Adamonis,~ !
Westinghouse, on May 11,1993: 1993 ISI Data on the Underclad Flaw Indications in the Sequoyah Unit 1 Reactor Vessel Nozzles.
- 5. Facsimile Transmittal from David Goetchus, TVA, to Rick Rishel, Westinghouse, j on July 13, 1993: Corrections to 1993 ISI Data on the Underclad Flaw ;
1 i Indications in the Sequoyah Unit 1 Reactor Vessel Nozzles.
MNA-29tLWPT:6/1593 I
l 1
1 I
TABLE 1 :
UNDERCLAD CRACKING TEST BLOCK FLAWS USED IN THE IABORATORY !
COMPARISON OF THE 1980 SUPPLEMENTAL PSI AND THE 1993 ISI TECHNIQUES t i
'I BLOCK CRACK LENGTH CRACK DEITH ASPECT RATIO i IDENTIFICATION (IN.) (IN.)
W-A-1 1.25 .23 5.4:1 -
W-A-2 .65 .11 6.0:1 :
i W-A-3 1.63 .31 53:1 i W-B-1 1.25 .23 5.4:1 :
W-B-2 .65 .11 6.0:1 i W-B-3 1.63 31 53:1 PS-1 .25 .11 23:1 !
PS-2 .58 .25 23:1 l PS-3 .76 33 23:1 APPENDIX VIII - 1.43 .14 10.2:1 j
] 1A :
APPENDIX VIII - 1.95 .14 13.9:1 IB 1
APPENDIX VIII - 1.93 .68 2.8:1 l 2A l APPENDIX VIII - 1.98 .68 2.9:1 2B SOURCE : Southwest Research Institute, Reference 1 l l
MNA-296.WPP 6/1593
TABLE 2 :
LABORATORY COMPARISON OF LENGTH SIZING METHODOLOGIES l
1 BLOCK MANUAL AUTO. ACTUAL MANUAL SwRI ID. PSI ASME/RG LENGTH PSI TECH.
TECH. 1.150 (IN.) TECH. LENGTH AMPL. TECH. LENGTH MEAS.
i
(%DAC) AMPL MEAS. ERRORA
(%DAC) ERRORM W-A-1 566 35 1.25 -0.22 -0.23 W-A-2 631 37.5 0.65 0.82 0.55 W-A-3 669 48.5 1.63 0.86- -0.13 W-B-1 318 25.5 1.25 -0.35 -0.55 W-B-2 238 46 0.65 0.82 0.45 l
W-B-3 355 37 1.63 -0.03 -0.24 i PS-1 596 24.5 0.25 0.25 0.10 PS-2 450 26 N 0.58 0.48 0.32 j PS-3 358 22.5 0.76 0.64 0.14 1A 312 28.5 1.43 -0.06 -0.26 1B 362 34 1.95 -0.02 -0.35 2A 19/ 39 1.93 -0.43 -0.83 2B 262 28.5 1.98 0.20 0.02 MEAN ERROR O.23 -0.08 NOTE (1): Lengths taken at 1/4 maximum amplitude.
NOTE (2): Lengths taken at 1/2 maximum amplitude.
SOURCE : Southwest Research Institute, Reference 1 MNA-2%WPFN1193
i s ,
j TABLE 3. , ,
LABORATORY COMPARISON OF DEPTH SIZING METHODOLOGIES i
BLOCK ID. ACTUAL DEPTH MANUAL PSI SwRI SLIC (IN.) TECHNIQUE TECHNIQUE ;
ERRORM ERROR W-A-1 0.23 0.11 0.01 W-A-2 0.11 0.38 0.08 l
W-A-3 031 0.52 0.05 i W-B-1 0.23 0.00 0.02 !
W-B-2 0.11 0.19 0.23 W-B-3 0.31 0.02 0.09 0.05 0.03 !
PS-1 0.11 PS-2 0.25 0.10 0.10 PS-3 0.33 0.13 0.09 1A 0.14 0.31 0.05 1B 0.14 0.50 0.03 2A 0.68 -0.18 0.06 2B 0.68 0.04 -0.05 m
0.06 l MEAN ERROR 0.17 Note (1): Estimated by using length divided by three.
SOURCE : Southwest Research Institute, Reference 1 MNA.2%WPF4'1593
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TABLF 4 : i ULTRASONIC TEST DATA ON THE SEQUOYAH UNIT 1 I
! REACTOR VESSEL NOZZLE UNDERCLAD FLAW l INDICATIONS,1980 SUPPLEMENTAL PSI EXAMINATION AND 1993 ISI EXAMINATION ,
I i
NOZ. IND. PSI ISI PSI ISI PSI ISI f ID. ID. %DAC %DAC LENG. LENG. DEPTH DEPTH 1 MAX. (IN.)W (IN.)W (IN.)@ (IN.) !
1 11 1 125 17 0.25 0.61 0.083 0.14 11 2 178 38 0375 0.70 0.125 0.24 )
II 3 75 ND 0.25 - -- 0.083 ---
10 1 75 ND 0.25 --- 0.083 ---
10 2 178 37 0.25 0.40 0.083 0.25 10 3 125 31 0.25 0.62 0.083 0.20 10 4 316 17 0375 0.40 0.125 0.19 10 5 316 ND 0312 --- 0.104 ---
! 21 1 251 32 s 0375 0.50 0.125 0.12 2I 2 282 25 0312 0.49 0.104 0.20 l
21 3 75 ND 0375 ---
.0.125' ---
l 2I 4 251 10 0.25 0.69 0.083 0.11- !
21 5 200 8 0.50 0.70 0.167 0.20 21 6 282 67 0375 0.40 0.125 0.09 21 7 159 ND 0.25 --- 0.083 ---
21 8 200 18 0.625 0.61 0.208 0.20 21 9 141 18 0.625 .0.61 0.208 0.20 2I 10 316 44 0.50 0.50 0.167 0.17.
21 11 282 .22 0312 0.50 0.104 0.20 21 12 178 ?.2 0375 0.60 0.125- 0.15 21 13 159 ND 0.25 --- 0.083 - - -
21 14 251 34 0375 0.57 0.125 0.18 11 15 282 42 0312 0.50 0.104 0.22 MNA-2%WPf%/1593
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21 16 125 ND 0.25 --- 0.083 ---
21 17 178 23 0.25 0.60 0.083 0.10 j 21 18 100 ND 0.25 --- 0.083 ---
l 2I 19 95 ND 0.25 -- 0.083 --
2I 20 141 ND 0.25 - 0.083 _ --
21 21 200 25 0375 0.60 0.125 0.22 31 2 224 25 0.4375 0.42 NG 0.11 31 1 80 ND 0312 --- 0.104 --
1 30 1 159 12 0375 NG 0.125 NG 1 l
30 2 159 8 0.375 NG 0.125 NG 30 3 200 10 0.50 NG 0.167 NG ,
30 4 125 14 0.375 NG 0.125 NG
! 30 5 100 ND 0.50 -- 0.167 ---
30 6 100 ND 0.50 -- 0.167 ---
l 30 7 251. ND 0.50 --- 0.167 ---
t 30 8 125 1Oj?f @ 0.375 NG 0.125 NG l f 30 9 141 ND 0.375 -- 0.125 --- t
( i 30 10 75 6 O.25 NG 0.083 NG !
30 11 100 ND 0.25 --- 0.083 -- I l
30 12 200 9 0375 NG 0.125 NG !
t 30 13 200 7 0.25 NG 0.083 NG !
30 14 178 ND 0375 -- 0.125 -
i 30 15 178 11 0375 NG 0.125 NG l 30 16 200 9 0.25 NG 0.083 NG {
30 17 200 10 0375- NG 0.125 NG ,
30 18 178 27 0375 0.59 0.125 0.13 j 30 19 251 23 0.50 0.60 0.167 0.24 ;
30 20 282 22- 0.50 0.59 0.167' O.10 j; 30 21 200 9 0.25 NG 0.083 NG l 30 22 251 14 0.25 NG 0.083 NG j 30 23 224 13 0.50 NG 0.167 NG l 41 2 112 ND 0.25 ---- 0.083 ----
l 1
MNA-296.WPF:W1193
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. 4I 4 200 24 0.281 0.49 0.094 0.16 1 l
41 5 80 9 0.25 0.49 0.083 0.09 ;
1 41 1 141 ND 0.375 --
NG --
41 3 100 ND 0.25 -- NG - - -
l 20 1 100 7 0.4375 NG NG _
NG t 40 1 125 ND 0.375 ---
NG ---
NOTE (1): Lengths taken at 1/4 maximum amplitude.
NOTE (2): lengths taken at 1/2 maximum amplitude.
NOTE (3): Estimated by using length divided by three.
NG : Not given.
ND : Not detected.
-- : No data. i SOURCE: TVA, Reference 4 i
1 MNA-2%WPf4/1593
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Source : Southwest Reseerth Instkete (May 1993) 1.0 o O PSI TECHNIQUE 0.8 -
O SwRI TECHNIQUE o
0.6 -..~,'%- ,
O PSI Technique
_ O ,,,, (-12dB drop) o O '.
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(4dB drop)
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-0.8 -
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O.0 0.5 1.0 1.5 2.0 2.5 3.0 IICTUAL LENGTli FIGURE 1 : Cesaponison of Raw Length S4 Ing Errors Using the 1980 (PSI) and 1993 (SwRI)
Length Sizing Methodologies ( 12dB, and -6dB dowp, respectively)
Sourre : Southwest Research Institute (May 1993) 1.0 O PSI TECHNIQUE 0.8 '
o SLIC TECHNIQLE 0.6 -
o o 0.4 -
o p3, 7,,,,,,,
g ,9,,,' (3:1 length to depth ratio) 0.2 -
o
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ry o.- o x
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oc m -0,2 - o ,
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SWRI Techaksee (suc)
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-0.8 -
-1.0 .
O.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.b RCTUAL DEPTHCIN)
FIGURE 2 : Comeparison of Flaw Depth Sizing Erron Using the 1980 (PSI) and 1993 (SwRI)
Depth Slaing Methodologies (3:1 lemath to depth ratio, and SLIC, respectively)
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LEGEND A The 10. 20, 30 year 10, 20, 30 yrs acceptable ficw limits.
A 20 A B - Within this zone, the I q surface flaw is acceptable 18 l [ by ASME Code analytical j j ! criteria in IWB 3600 16 l l C - ASME Code allowable since j
1983 Winter Addendum
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o II I jIl I o 0.040.080.120.16 0.2 0.240.280.320.360.4 0.44 0.48 FLAW SHAPE (a/f) _ . . . ,
i Figure A-15.2 Evaluation Chart for Outlet Nozzle Bore Region X Inside Surface X Surface flaw X Longitudinal Flaw Outside Surface Embedded flaw Circumferential flaw FIGURE 3 :
Flaw Evaluation Chart for Flaw Indicallons Found in the Sequoyah Unit i Outlet Nonle hre Realon (Source: Wes Inghouse WCAI'-134Mn
I l . .
l LEGEND A - The 10, 20, 30 year acceptable flaw limits.
r A B - Within this zone, the 20 surface flaw is acceptablo by ASME Code analytical 18 critoria in Iwa-3600 C - ASME Code allowable since 16 1983 Winter Addendum
[ g4 D - ASME Code allowable prior to 1983 Winter Addendum
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0 0 0.04 0.08 0.12 0.16 0.2 0.240.280.320.36 0.4 0.44 0.48 FLAW SHAPE (a/A) c o i. ,
figure A-14.2 Evaluation Chart for inlet Nozzle Bore Reg'.on X Inside Surface X Surface Flaw X Longitudinal Flaw Outside Surface Embedded Flaw Circumferential flaw FIGURE 4 : Iqaw Evaluation Chart for Flaw Indications Found in the Sequoyah Unit i Inlet Noule Bore Hestlan (Sourre: Westinghouse WCAP-13668)
l ENCLOSURE 2 TVA Commitments
(Surveillance Instruction 114.1) by March 9,1995, to include an augmented inspection requirement of the Unit I reactor vessel nozzles i for underclad cracks. The augmented examination technique will be at least as sensitive as that used to conduct the examination during the Unit 1 Cycle 6 refueling outage. The Unit 1 Cycle 6 examination will ,
serve as a baseline examination for the augmented examination that will be performed at the end of the cecond 10-year ISI interval for Unit 1. !
- 2. TVA will submit to NRC the results of the augmented examination of the Unit I reactor vessel nozzles. These results will be submitted within six months from the end of the second 10-year ISI interval for Unit 1.
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