ML20197B424

Reactor Pressure Vessel Preservice Ultrasonic Exam Limitations at Sequoyah Nuclear Plant,Unit 1, Supplemental Rept

ML20197B424
Person / Time
Site:	Sequoyah
Issue date:	01/31/1986
From:	Flach W, Mengden F SOUTHWEST RESEARCH INSTITUTE
To:
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ML20197B411	List: ML20197B408 ML20197B424 ML20197B430
References
NUDOCS 8605130027
Download: ML20197B424 (16)

Text

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REACTOR PRESSURE VESSEL PRESERVICE ULTRASONIC EXAMINATION LIMITATIONS AT SEQUOYAH NUCLEAR PLANT, UNIT 1 I

l Supplemental Report SwRI Project 17-5339 j- cn. E k k 'if 9 M Prepared for Tennessee Valley Authority 1750 Chestnut Towers II Chattanooga, Tennessee 37401 l

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I January 1986 Prepared by Approvfby ,,

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F. C. d. .Mengcen s

Wayne T. F4'acn d

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• Group teacer Oepar- ent of Ingineering Ier rices Director /

. Cepart=ent of Engineering Services Sondestructive Evaluation Science and Technology Division k

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1. BASIS FOR REPORT Southwest Research Institute (SwRI) performed an ultrasonic (UT) preservice examination (PSI) of Tennessee Valley Authority's (TVA) Sequoyah Nuclear Plant, Unit 1, reactor pressure vessel (RPV) during January of 1979. Except for examination 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 attachments) and an automated Data Acquisition System (DAS).

The RPV PSI results are reported in SwRI Final Report 17-5339: "Preservice Examination of Selected Class 1 Components of the Sequoyah Power Station, Unit 1," issued March 1979. The UT examinations revealed insignificant and geometric indications as well as other indications in the RPV closure head that were reportable by Code. 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.

%o (2) Section XI of the ASME 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 1,"

78-TVA-SNP-1-1-0, dated December 1978.

(5) SwRI " Plan for Mechanized Ultrasonic Examination of Selected 3

Components at Sequoyah Power Station, Unit 1," dated January 1979.

(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 perfor=ed a comprehensive review of the 1979 PSI data to further describe and quantify the examination limitations which were experienced. The results of that tata review are summarized in this supple-mental report.

SwRI has continued to refine mechanized examination techniques an: equi; ment suca that many of the exauinatica limitations experienced during tha Eequoyan Unit 1231 wil; be menimized during future inservice e::aminati:ns usin; curran:iy applied techniques.

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2. DESCRIPTION OF EXAMINATION LIMITATIONS Two generic types of limitations were encountered sost frequently during the PSI of the Sequoyah Unit 1 RPV welds and components:

(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. J' Although current SwRI procedures require full vee path and shallow-angle search unit scans to compensate for the limitations encountered in the near surface, this general limitation was experienced throughout the Sequoyah Unit 1 PSI. However, it involved less than 2.5% of the weld exasination volu=e for 45-degree techniques and 6.5% of the weld examination volume for 60-degree techniques. Generally, interface noise inhibited resolution capabilities at the near surface for about 1.0 inches or less of sound (setal) path for shear-wave examination and 1 inch to 2 inches of setal path for longi-tudinal-wave examinations. It should be noted that electronic gating did not result in any examination limitations since the entire instrument screen pre-sentation was sonitored during the exasination, videotaped, and reviewed independently following the exasinations.

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 lisi-cation encountered during the Sequoyah Unit 1 RPV PSI.

The attached tables and figures detail the exasination limitations experienced during the Sequoyah Unit 1 RPV PSI. Specifically, the tables quantify the limitations in ter=s 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 setal and associated base material.

2.1 RPV Lower Head Welds Parallel and transverse scans of Bottos Head Cap-to-Spherical Ring Weld WOL-02 were limited due to interference with in-core instrumentation tubes. Additional limitations to volusetric coverage were experienced due to noise encountered at the sound beas entrance point. Table i lists the percent ci 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 barrel support lugs.

WOl-02 was not exasined from the inside surface of the bottom head cap due to instru=entation tubes. iOl-02 was examined from the outside surface of the vessel using manual ultrasonic sethods and obtained full coverage of the requirad weld voluse.

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. 3 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 noise. 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.

Except for near surface interface noise, there were no examination limitations for Lower Shell-to-Upper MiddleShell-to-Lower Middle Shell Weld WO3-04 and Lower Middle Shell Weld WO4-05.

3 Examination limitations of Upper Middle Shell-to-Upper Shell Weld WOS-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 azimuchs of scan limitations due to the proximity of the reactor coolant nozzles.

Upper Shell-to-Flange Weld WO6-07 was limited due to core barrel anti-rotation keyways at the top of the vessel and reactor coolant nozzles below the veld. 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 care experienced during the transverse examinations from the vessel wall.

Due to weld joint location and nozzle configuration,' full transverse examination coverage of the volu=e of base metal on the nozzle side of the weld was not possible.

2.a RPV Closure Head Welds The RPV Closure Head welds were examined manually from the outside surface. Table 4 lists the volume of material not eff2ctively examined.

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.p Figure 5 depicts limitations in a section of the Closure Head Weld WO8-09, Flange-to-Head weld. 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 Weld WO9-10. These examinations were limited as shown due to interference from the lifting lugs and the insulation support ring.

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3. CONCLUSION

. Limitations to complete coverage of ASME Code-required examination volumes were experienced during the Sequoyah Unit 1 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 extent of ultrasonic examination limitations will be greatly reduced during future inservice examinations of the Sequoyah Unit 1 RPV using currently applied examination techniques.

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. s Table 1 LOWER HEAD WELD LIMITATIONS Percent of Volume Figure Weld No. Examination Angle Not Effectively Examined No.

W01-02 0* *28.34 1 45' *45.09 1 60* *58.93 1 45*T *87.69 1 60*T *87.69 1 W2-A 0* 53.90 1 45' 24.42 1 60* 17.32 1 45'T 9.77 l' 60*T 4.79 1 W2-3 0* 44.86 1 45' 11.41 1 60* 9.42 1 45*T 4.16 1 60*T 0.68 1 W2< 0* 60.20 1 45* 19.05 1 60* 12.80 1 45'T 15.92 1 60*T 4.79 1 W2-D O' 45.70 1 45* 9.13 1 60* 9.11 1 45*T No Limitations 1 60*T No Limitations 1 W2-E 0* 46.39 1 45* 11.05 1 60* 9.90 1 45*T No Limitations 1 60*T No Limitations 1 W2 -F 0* 45.19 1 45* 12.16 1 60* 13.44 1 45'T No Limitations 1 60*T No Limitations 1 WO2-0. 0* 42.56 1 45* - 30.35 1 60* 13.98 1

45'T 31.01 1 60*T 30.55 1

• Qmplete coverage was established by using manual *.~" method from tessel outside surfaca.

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-Table 2 -

RPV CIRCLE'ERENTIAL 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* 24.91 2 45* 2.51 2 60* 15.02 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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RPV N0ZZLE Tr.LD LIMITATIONS Percent of A-B-C-D-E Volume Figure Examination Area Examination Type Not Ef fectively Examined No.

Inlet Nozzles Parallel Scans 45* - 7.34 3 15* - 54.58 3 Inlet Nozzles Transverse Scans *45 'T - 68.43 3

• 60*T - 68.43 3 Outlet Nozzles Parallel Scans 45* - 10.38 4 10* - 35.50 4 Outlet Nozzles Transverse Scans *45 *T - 7 5.38 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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Table 4 RPV CLOSURE HEAD CIRCLMFERENIIAL WELD LIMITATIONS Percent of Volume Figure Wald 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' A

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