ML20062F967

Evaluation of Indication in J Farley Unit 2 Steam Generator C Upper Shell to Transition Cone Girth Weld

ML20062F967
Person / Time
Site:	Farley
Issue date:	11/30/1990
From:	Bamford W, Rishel R WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML19310C929	List: ML20062F957 ML20062F967 ML20062F968 ML20062F976 ML20062F978
References
MT-MNA-387(90), MT-SMT-097(90), MT-SMT-97(90), NUDOCS 9011280289
Download: ML20062F967 (16)

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{{#Wiki_filter:_ _. a MT-MNA-387(90) i l MT-SMT-097 ( 90) H erY t n R E 1 1 i l l l t l l 4 EVALUATION OF AN INDICATION IN THE JOSEPH FARLEY UNIT 2 STEAM GENERATOR C UPPER SHELL TO TRANSITION CONE GIRTH WELD i i NOVEMBER 1990 4 R. D. RISHEL W. M. BAMFORD HEVIEWED BY: D. S. Drinon Metallurgica & NDE Analysis APPROVED BY: _<t-i D. C. Adamonis, Manager Materials, Mechanics & l Diagnostics Technology i Westinghouse Electric Corporation Energy Systems -s P.O. Box 2728 Pittsburgh, PA-15230-2728 l 1 l 9011280280 901120 PDR ADOCK 05000364 P PDC l . u.

l SECTION 1.0

SUMMARY

During the Fall 19'A0 ultrasonic examination of the Farley Unit 2 steam generator C upper shall to transition cor.s girth weld (weld

1. 5), one recordable indication exceeded the acceptance criteria.

This indication was detected with the 60-degree, 2.25 MHz shear wave examination. The location of this indication in the weld, 1 past experience with the same weld in other steam generators at other plants, and supplemental examinations performed on chis steam generator indicate that this indication is subsurface in nature (i.e., a group of small weld inclusions and/or voids). An evaluation of this indication (using -6 dB drop or half maximum amplitude sizing criteria) to the acceptance standards in Table IWB-3511-1 of the ASME Code Section XI (1983 Edition with the Summer 1983 Addenda) results in this indication exceeding the standards. Using the fracture analysis rules of IWB-3600 and the guidelines of Appendix A, both from the ASME Code Section XI, 1983 Edition with the Summer 1983 Addenda, this indication is acceptable. These examinations were performed with the same Westinghouse personnel and procedures utilized on numerous other plants. These other plants exhibited both inner diameter cracking conditions, l subsurface fabrication flaws, or a combination of both at the 1 i recording levels established in the test procedures. The evaluation of examination data and the performance of supplemental investigations were conducted by engineering personnel directly involved with the evaluation of data from the same plants as discussed above. l

B000d on ooticfoctcry vicual cx3cinntien of th3 v31d in3ido curfcco and the absence of inside surface ultrasonic indications, Westinghouse concludes that the cracking experienced at other plants is not occurring in the Parley Unit 2 Steam Generator C. ) t i l l l L i I 7 i

f 1 l 1 l* SECTION 2.0 i l NONDESTRUCTIVE EXAMINATION RESULTS I 2.1 Auemented Instrvice Insoection - 1990 Examinations i During the Fall 1999 outage steam generator upper shall to transition cone girth weld augmented inspection, one indication that exceeded the 50% DAC recording level and the acceptance standards of the ASME Code Section XI (1983 Edition up to and including the Summer 1983 Addenda) was found. This indication is located in Steam Generator C Weld i

1. 5 approximately 26" counterclockwise from the centerline of the feedwater nozzle.

This weld is shown in the elevation view of Figure 2-1. This weld was selected because it had not been previously examined by ultrasonic inspection techniques, preservice or inservice. This indication was detected with a 60-degree, 2.25 MHz shear wave examination directed downward from the shell side, and sized with a 4.0 MHz' transducer. A summary table of sizing data providing the measured "2a" value, the measured "S" value, and the measured length, all with respect to the l normal to the inside pressure retaining surface of the 4 l component is provided as Table 2-1. These results were obtained using a 4.0 MHz transducer and a ~6 dB drop or half maximum amplitude sizing criteria. The evaluation scheme satisfies the-flaw indication characterization criteria provided in IWA-3300 and Table IWB-3511-1 of Section XI. The primary sizing dhta used for the fracture mechanics analysis was based on that taken with the 4.0 MHz' transducer. Experience has shown that 2.25 MHz testing using a 0.5" x 1.0" transducer is excellent for detection in this application, but tends'to oversize when used in conjunction-with the Section XI criteria and volumetric-type embedded reflectors. L

-..-,.~.-__ _m. l* Tho 2.25 MHz, 0.5# x 1.08 trcn2ducOr produc30 o beam cproad which is wider than that of a similar size 4.0 MHz 1 transducer. This typically results in an unavoidable overestimate of the true size of volumetric reflectors such as weld inclusions, which are believed to be present in this case. Since the flaw indications are much smaller than the measured beam size, effectively the measured size is a l function of this beam spread rather than the true dimensions of the discontinuities. i Therefore, in the case of weld inclusions a reduction in beam rpread is desired to obtain a more realistic size. There-are n number of ways to minimize the beam spread, including use of a higher frequency transducer, a focused transducer, a larger transducer size or a combination of these. The use of other transducers is permitted by Paragraph T-451.1 of the ASME Code Section V, Article 4 which states that "other ultrasonic techniques and nondestruative examination methods may be helpful in determinity a reflector's true position, size, and orientation'. The raw indication data-from the examinations in steam generator C clearly indicate that the detected reflector is embedded rather than surface. This is seen in the location of the peak response (see Figure 2-2'. The peak response is r.ot observed at or near the inner diameter surface which would be expected for a surface breaking flaw.--Supplemental investigations including review of construction radiographs - i and visual examinations of the inner diameter surface were performed. No relevant flaw-type images were noticeable on l the construction radiographs encompassing the area where this L indication is located. L l l ) L

) i Tho viousi cxcainstion3 cn tha inn:r dicacter curfcco in tho vicinity of this indication and over approximately 100% of { 2 l the weld revealed that no pitting or linear indications were l present. These supplemental investigations confirm that this indication is not surface-related.- The indication is likely a result of weld discontinuities lying within 1" of the inner diameter surface. Furthermore, the absence of pitting or i l linear indications on the ID surface suggests that the Farley Unit 2 steam generator C weld #5 is not experiencing the' ) cracking found at other plants. All examination data, therefore, nicarly suggest embedded type discontinuities. 2.2 Excerience with other Plants The indication in steam generator C at Farley Unit 2 appears to be quite characteristic of experience with various welds In steam generators and pressurizers at other plants where preservice ultrasonic examination'results (based on 2.25 MHz, shear wave, 50% DAC sizing methods) showed reflectors in weld j backchip regions which had dimensions in excess of those allowable values provided in Section XI of the ASME Code. Attempts were made at other plants to confirm the size, location, and orientation of these indications by complementary nondestructive examination methods, i.e. O j I degree longitudinal wave examinations,.and both fabrication and field radiography. No reliable responses could be observed from the shear wave indications using the straight beam examinations. In terms of the radiography, the fabrication radiographs of the areas in question were reviewsd~with no conclusive results. Additionally, field radiography was performed in selected areas at these plants but again no confirmation of the shear wave examination indications could be obtained. 4 j i

l Thoco inctncluoivo rc3ulto 1cd to phyoical r0 oval of com3 of the suspect indications by mechanical means for complete j metallurgical characterization. l The indications were found to have been caused by small slag inclusions and voids between weld passes in the weld backchip [ area near the inside surface. Measurements made during the i destructive analysis showed that the ultrasonic sizing using 2.25 MHz, shear wave,. 50% DAC sizir ; methods exaggerated the l true size of the discontinuities in terms of length and/or through-wall dimensions, i Furthermore, this experience correlates well with investigations to date which have shown that when sizing volumetric-tvoe reflectors by amplitude drop methods, i.e. 2.25 MHz, 50% DAC, the typical result is that the beam size rather than the reflector size is measured. For example, the lower-the test frequency, the larger the beam width, 4 resulting in a larger than actual apparent flaw size (1-6). i 2.3 Evaluation Results 1 Since the data clearly suggest embedded reflectors at Farley Unit 2, the use of a more realistic volumetric flaw sizing approach was implemented. This sizing approach consisted of using a 4.0 MHz transducer and a -6 dB or half maximum amplitude sizing criteria. The angle used in sizing was dependent on the angle which detected the indication. The 4.0 MHz transducer resulted in a smaller beam spread in comparison with the true size of the suspect reflectors. The -6 dB or half maximum sizing criteria was selected because it has provided the better accuracies when compared with 50% DAC or 20% DAC sizing levels (7). j u

i Using tho 4.0 MHz dato in Tcblo 2-1, ovolustion ecleulctiono were performed. This evaluation compared the characteristics l of the 4.0 MHz sizing data to the acceptance standards described in Table IWB-3511-1 of the ASME Code Section XI, i 1983 Edition with the summer 1983 Addenda. This evaluation resulted in the indication exceeding the standards. Table 2-2 summarizes this evaluation. The indication is classified 1 as subsurface. 2.4 References 1.

Gruber, G.

J., Hendrix, G. J. and schick, W. R., " Characterization of Flaws in Piping Welds Using Satellite Pulses", Materials Evaluation, April 1984. 2. Cook, R. V., Latimer, P. J. and McClung, R. W., Plaw Measurement Usina' Ultrasonics in Thick Pressure Vessel Steel, final report on Contract No. W-7405-eng-26, prepared by Oak Ridge National Laboratory-for the U.S. Nuclear Regulatory Commission, Aug. 1982, Oak Ridge, TN. 3.

Doctor, S.

R., Becker, F. L.,

Haasler, P.

G. and Selby, G. P., " Effectiveness of U.S. Inservice Inspection Techniques - A Round Robin Test", Proceedinas of i Eggcialist Meetina on Defect Detection and Sizina, i Ispra, Italy, May 3-6, 1983, Joint Research center, Ispra (Va), Italy, i 1 4. Jessop, T. J.,-Mudge, P. J. and Harrison, J. D., Ultrasonic Measurement of Wald Flaw Sire, National Cooperative Highway Research Program Report 242, ) prepared for the Transportation-Research Board by The Welding Institute, Dec. 1981, The Welding. Institute, Cambridge, England. i

i 5. Mudgo, P. J. Cnd Jocorp, T. J.,

1. Sizo MOccuremOnt and Characterization of Wald Defects by Ultrasonic Testing:

Findings of a Collaborative Programme", Proceedinas of NDE in Relation to Structural Intearity, Paris, France, l Aug. 24-25, 1981, Applied Science Publishers, Ltd., l London, England. 6. Rishel, R. D., " Summary Report: Volumetric Flaw Depth Sizing", MT-SMART-807, September 12, 1985 (submitted to Seabrook Power Station). t 7. Willetts, A. J., Ammirato, F. V., and Kietzman,-E. K., Jones, J. A., Applied Research Company, Accuraev of Ultrasonic Flaw SiEina Techniaues for Reactor Pressure Vessels, EPRI RP1570-2 Draft Interim Report, March 1988.- ? 9 i L -. ~, ~ ~ ~ -.

I i TABLE 2-1

SUMMARY

OF INDICATION DIMENSIONS Technicrue L 1 1 4.0 MHz, half maximum 0.35" 0.46" 4.0"* amplitude

• Length was measured conservatively from baseline to baseline.

I e P h 'l

i TABLE 2-2 EVALUATION OF INDICATION TO TABLE IWB-3511-1 CRITERIA l Subsurface a/t a/t* ._21 L a L. or surface all Allow. Act. 0.35" 4.0" 0.46" 1.0 Subsurface 0.044 2.77% 4.7%

• t = 3.72" e -,

.~ t 3 423 9 o o i 43 26 3 62 194 60 8.D r j j b E 113 49 q !f = 8 j - Wo o ~~ m u t -] [ ] .MbM 11349 i. )@ r" ,j weld #$ # g 7694 3 84 \\ i - f, i g 356 b U C t 812 00 2 82 - 129 1.D il hi 123.50 o D Hl 'l ( l 38 il J l i I i l l

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i 14 00 ' p ll' 4 n '8 70 ,l t' - r o 't { [' 27 00 4 O ^ 62 61 1 00, $d 06.00 _ l '__ l 31.20 p u FIGURE 2-1 Geometry of Farley Steam Generator C, showing the Upper Shell to cone Girth Wald Region. 1 I l 1 4-, , ~. -

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'l SECTION 3.0 l RESULTS OF FRACTURE EVALUATION l l The indication in the upper shell to transition cone girth weld was found to exceed the allowable standards of the ASME Code, and therefore, was subjected to a fracture mechanics evaluation. The fracture mechanics analysis methods and material properties are documented in WCAP-12211, entitled " Background and Technical Basis, Handbook on Flaw Evaluation for the Farley Units 1 and 2 Main Coolant System and Components", published in September of 1989. The fracture analysis results have been published in the form of-flaw evaluation charts, which allow the indication to be evaluated for acceptability by simply plotting its size as a point on the chart. The flaw evaluation chart used here has been taken-from C WCAP-12213 Rev. 1, entitled, " Handbook on Flaw Evaluation for Joseph Farley Units 1 and 2 Steam Generators and Pressurizers", published in July 1990. Using the appropriate flaw evaluation chart from WCAP-12213 Rev. 1, Appendix Section A-6, the indication was found to be acceptable, as q seen in the attached copy of Ff.gure A-6.4. The dimensions of the indication, as sized by the final inspection with the 4.0 MHz frequency are given below: 2a = 0.35" a = 0.175" S = 0.46" l = 4.0" t = 3.72" 6 = S + a = 0.635 h = 0.17 f=0.047 l l t f*'

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