ML20197B430
| ML20197B430 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/31/1986 |
| From: | Mengden F SOUTHWEST RESEARCH INSTITUTE |
| To: | |
| Shared Package | |
| ML20197B411 | List: |
| References | |
| NUDOCS 8605130030 | |
| Download: ML20197B430 (20) | |
Text
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. i REACTOR PRESSURE VESSEL PRE 3ERVICE ULTRASONIC EXAMINATION LIMITATIONS AT SEQUOYAH NUCLEAR PLAKr. UNIT 2
. Supplemental Report SwRI Project 17-6037 I
Prepared for Tennessee Valley Authority 1750 Chestnut Towers II Chattanooga, Tennessee 37401 January 1986 Prepared by Approv by
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BASIS FOR RdPORT Southwest Research Institute (SwRI) performed an ultrasonic (UT) preservice examination (PSI) of Tennessee Valley Authority's (TVA) Sequoyah Nuclear Plant, Unit 2, reactor pressure vessel (RPV) during December 1980.
Except for exami-nation of the closure head and bolting and supplemental examinations of the lower head welds, the RPV UT examinations were performed from the vessel inside surfaces using mechanized positioning equipment (par Device and SwRI attach-ments) and an automated Data Acquisition System (DAS).
The RPV PSI results are reported in SwRI Final Report 17-6037:
"Preservice Examination of Selected Class 1 Components of the Sequoyah Power Station, Unit 2,"
issued April 1981.
The UT examinations revealed insignificant and geometric indications as well as indications which were evaluated by SwRI as being Code-acceptable.
The examinations were conducted in accordance with the following documents:
(1)
Contract No. 64-148315 for " Baseline and Inservice Inspections of Reactor Vessels" issued by TVA to SwRI, dated June 1, 1978.
(2)
Section XI of the 4SME Boiler and Pressure Vessel Code, " Rules for Inservice Inspection of Nuclear Power Plant Components," 1974 Edition with Addenda through Summer 1975.
(3)
Section V of the ASME Code, " Nondestructive Examination," 1974 Edition with Addenda through Summer 1975.
(4)
SwRI " Project Plan for the Preservice Examination of Selected Class 1 Components of Sequoyah Power Station, Unit 2,"
80-TVA-SNP-2-1-0, dated July 1980.
(5)
SwRI " Plan for Mechanized Ultrasonic Examination of Selected Components at Sequoyah Power Station, Unit 2," dated September 1980.
(6)
U.S. Nuclear Regulatory Commission Regulatory Guide 1.65, " Materials and Inspection for Reactor Vessel Closure Studs," dated October 1973.
(7)
SwRI Nuclear Quality Assurance Program Manual, Revision 1.
Limitations to examination coverage were experienced during the PSI of the RPV and are generically identified in the SwRI Final Report previously referenced.
In response to TVA's request for additional information concerning examination limitations and in anticipation of meeting the reporting requirements of the U.S. Nuclear Regulatory Commission Regulatory Guide 1.150 for future inservice RPV examinations, SwRI has performed a comprehensive review of the 1980 PSI data to further describe and quantify the examination limitations which were expe-tenced.
The results of that data review ara summarized in this supple-nan:21 repor.
SwRI has continued to refine mechan.:ed examination techniques 2nd equipmen: such : hat many of the examination lim.:ations experienced during the 3equoyah Unit 2 PSI will be minimized during fu:ure inservice axaminations using currently applied tacaniques.
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DESCRIPTION OF EXAMINATION LIMITATIONS Two generic types of limitations were encountered most PSI of the Sequoyah Unit 2 RPV welds and components:
frequently during the (1)
Interference from search unit wedge-to-component near surface interface noise, and (2)
Component geometric interference with the scanning equipment and/or geometric shadowing of examination areas.
Although current SwRI procedures require full vee path and shallow angle search unit this general limitation was experienced throughout the Sequoyah Un However, it involved less than 2.5 percent of the weld examination volume for 45 degree techniques and 6.5 percent of the weld examination volume for 60-degree techniques. Generally, interface noise inhibited resolution capa-bilities at for shear-wave examination and 1 inch to 2 inches of metal path tudinal-wave examinations.
It should be noted that electronic gating did not result in any examination limitations since the entire instrument s
screen pre-sentation was monitored during the examination, videotaped, and reviewed independently following the examinations.
Recent improvements in equipment design (such as multiple device pivot points and redesigned search unit modules) have greatly reduced limitations due to geometric shadowing and/or component geometric interference.
However, this-type'of inherent interference presents the most significant examination limi-tation encountered during the Sequoyah Unit 2 RPV PSI.
The attached tables and figures detail the examination limitations experienced during the Sequoyah Unit 2 RPV PSI.
Specifically, the tables quantify the limi-L tations in terms of percent of Code-required examination volume which was not effectively covered.
The accompanying figures graphically ~ depict the location and extent of the limitations with respect to weld metal and associated base material.
2.1 RPV Lower Head Welds Parallel and transverse scans of Bottom Head Cap-to-Spherical Ring Weld W01-02 were limited due to interference with in core instrumentation tubes.
Additional limitations to volumetric coverage were experienced due to noise encountered at the sound beam entrance point. Table 1 lists the percent of required examination volume not effectively examined for each lower head examination. Figure 1 depicts a layout of the lower head 'and shows the surface area not covered due to instrumentation tubes and core harrel support lugs.
W01-02 was not examined from the inside surf ace of the cottom head cap due to 1.strumentation tubes.
W01-02 was examined fr:m the outside surface of the tassa'. using manual ultrasonic metaods and obtained full coverage of the raquir ed weld velame.
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s Examination of the Lower Head Meridional Welds W2-A, B', C, D, E, and F were limited due to instrumentation tube interferences, core barrel support lug interferences and near surface interface nof.se. The percent of required exami-nation volume not covered is provided in Table 1.
Figure 1 is a rollout view of the lower head showing areas of module limitations for 360 degrees of vessel azimuth.
Examination of Bottom Head-to-Lower Shell Weld WO2-03 was limited due to core support lugs and near surface noise to the extent listed in Table 1.
Figure 1 is a rollout view of scan surface limitations due to the core support lug interferences.
2.2 RPV Shell Circumferential Welds Table 2 lists the percent of Code-required weld volume not effectively scanned for each circumferential shell weld examination.
.i Except for near surface interface noise, there were no examination limitations for Lower Shell-to-Lower Middle Shell Weld WO3-04 and Lower Middle Shell-to-Upper Middle Shell Weld WO4-05.
Examination limitations of Upper Middle Shell-to-Upper Shell Weld WO5-06 were due to interference from the reactor coolant nozzles and near surface interface noise. Figure 2 is a rollout view of the examination area showing azimuths of scan limitations due to the proximity of the recirculation nozzles.
Upper Shell-to-Flange Weld WO6-07 was limited due to core barrel antirotation keyways at the top of the vessel and reactor coolant nozzles below the weld.
Figure 2 is a rollout view of the upper shell which includes Weld WO6-07.
2.3 Reactor Coolant Nozzle-to-Shell Welds The reactor coolant inlet and outlet nozzles were examined from the nozzle bore as well as the vessel wall. Table 3 lists the volume of material not effectively examined from the bore or vessel wall. The limitations experienced were typical for each inlet or outlet nozzle, respectively.
Interface noise did not significantly obscure examination coverage of the shell or bore near surface as the two examination approaches complemented one another.
Figures 3 and 4 are section views of the inlet and outlet nozzles, respectively. The most significant limitations to coverage of the Code-required examination volume (A, B, C, D, E) in the inlet and outlet nozzles were experienced during the transverse examinations from the vessel wall. Due to weld joint location and nozzle configuration, full transverse examination coverage of the volume of base metal on the nozzle side of the weld i
.was not possible.
f 2.4 RPV Closure Head Welds The RPV Closure Head welds ware examined =caually :::a the outside surface. Table 4 lists the volume of material noc effec::vely examined.
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Examination of the Flange-to-Head weld could not be conducted from the flange side due to the flange configuration and was limited from the head side due to interference from the lifting lugs.
Figure 5 is a section view showing limitations to examination of Closure Head-to-Dollar Plate Wald WO9-10.
These examinations were limited as shown due to interference from the lifting lugs and the insulation support ring.
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CONCLUSION
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Limitations to complete coverage of ASME Code-required examination volumes were experienced during the Sequoyah Unit 2 RPV preservice examination due to both component configuration and system design restrictions. The extent of these examination limitations is identified in this report. Many of the areas not effectively examined during the RPV PSI were radiographed during fabrication.
Due to refinements in equipment design and SwRI examination procedures, the of ultrasonic examination limitation will be greatly reduced during extent future inservice examinations of the Sequoyah Unit 2 RPV using currently applied examination techniques.
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Table 1 LOWER HEAD WELD LIMITATIONS Percent of Voluma Figure Weld No.
Examination Angle Not Effectively Examined No.
WO1-02 0*
- 54.18 45*
1
- 48.21 60*
1
- 51.12 1
45 'T
- 61.36 1
60 *T
- 60.48 1
W2-A 0*
53.90 45*
1 24.42 60*
1 17.32 45*T 1
9.77 60*T 1
4.79 1
W2-3 0*
44.86 45*
1 11.41 60*
1 9.42 45*T 1
4.16 60 *:
1 0.68 1
W2-C 0*
60.20 45*
1 19.05 60*
1 12.80 45 *!
1 15.92 1
60*:
4.79 1
W2-D 0*
45.70 45' 1
9.13 60*
1 9.11 45*~
1 No Limitations 1
60 *~
No Limitations 1
W2-E 0*
46.39 45*
1 11.05 60*
1 9.90 45*:
1 No Limitations 1
60*:
No Limitations 1
W2-F O'
45.19 1
45*
12.16 60*
1 13.44 45*!
1 No Limitations 1
60*T No Limitations 1
WO2-03 0*
42.56 1
45' 30.35 1
60' 13.38 1
a.' ':
31.01 1
6; *:
30.55 1
Completa coversge was aanblisaed by asing manual UT =e nod from vessel outside. surface.
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Table 2 RPV CIRCUMFERENTIAL SHELL WELD LIMITATIONS Percent of Volume Figure Weld No.
Examination Angle Not Effectively Examined No.
WO3-04 0*
26.40 6
45*
2.51 6
60*
6.49 6
45'T 2.51 6
60*T 6.49 6
WO4-05 0*
26.40 6
45*
2.51 6
60*
6.49 6
45'T 2.51 6
60*T 6.49 6
WO5-06 0*
27.50 2
45*
2.51 2
e 60*
22.45 2
45'T 2.51 2
60*T 6.49 2
WO6-07 0*
20.49 2
45*
3.59 2
60*
5.58 2
45'T 1.75 2
60*T 4.49 2
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Table 3 RPV N0ZZLE WELD LIMITATIONS Percent of A-B-C-D-E Volume Figure Examination Area Examination Type Not Effectively Examined No.
Inlet Nozzles Parallel Scans 45'
- 7.34 3
15' - 54.58 3
Inlet Nozzles Transverse Scans
- 45*T - CS.43 3
- 60*T - 68.43 3
Outlet Nozzles Parallel Scans 45*
- 10.38 4
10*
- 35.50 4
Outlet Nozzles Transverse Scans
- 45'T - 75.38 4
- 60 *T - 75.38 4
Transverse examinations not performed from the nozzle forging side due to nozzle configuration. These percentages include the areas which were not examined.
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. 9 Table 4 RPV CLOSURE READ CIRCUMFERENTIAL WELD LIMITATIONS Percent of Volume Figure Weld No.
Examination Angle Not Effectively Examined No.
WO8-09 0*
52.09 5
45*
18.92 5
60*
12.09 5
45*T 52.56 5
60*T 52.39 5
WO9-10 0*
5.29 5
45' 5.31 5
60*
5.31 5
45'T 0.90 5
60*T 0.54 5
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REACTOR VESSEL LOWER HEAD DOLLAR WELD EXAMINATION ESTIMATED MAN-HOURS Item Description Hours Men 1
Build scaffolding 8.00 2
2 Safety inspection 0.25 1
3 Health physics surveys 1.00 1
4 Remove insulation 24.00 2
5 Perform examinations 9.00 3
6 Replace insulation 32.00 2
7 Remove scaffolding 4.00 2
Total man-hours 164.25 RME:JLR 04/01/86 0649y 4
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