ML20214Q464
| ML20214Q464 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 09/18/1986 |
| From: | Ebneter S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 8609240367 | |
| Download: ML20214Q464 (10) | |
Text
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d SEP 181986 Docket No. 50-277 Philadelphia Electric Company ATTN:
Mr. John S. Kemper Vice President Engineering and Research 2301 Market Street Philadelphia, Pennsylvania 19101 Gentlemen:
Subject:
Investigation of Transverse Linear Indications in Longitudinally Welded Austenitic Stainless Steel Pipe from Peach Bottom Unit 2 During inspection of pipe replacement activities at Peach Bottom Unit 2 an unresolved item (277/85-04-02) resulted from identification of radiographic indications on the longitudinal welds of 1.5" thick X 28" 0.D. SA 358 Grade 316 pipe. These indications were 1/4" to 3/8" long, oriented transverse to the weld direction. The indications were evaluated by General Electric Company as reported by E. T. Ishizaka to R. L. Lebre on February 22, 1985 at the request of PECo and found to not represent a weld integrity or metallurgical condition but rather the result of X-Ray diffraction.
The NRC, Region I obtained a sample of pipe containing these radiographic indications for separate analysis. This sample was submitted to the Oak Ridge National Laboratory (0RNL) for examination and testing. The resulting report which confirms no adverse condition to exist in the weld with this radiographic indication as transmitted to NRC Region I on August 4, 1986 is attached. We request that you have the ORNL report reviewed, compared to the PECo findings and discuss the results with E. H. Gray (215-337-5325) of my office.
The response requested by this letter is not subject to the clearance procedures of the Office of Management and Budget as required by the Paperwork Reduction Act of 1980, PL-96-511.
Your cooperation with us in this matter is appreciated.
Sincerely, orisimi sigr.ed Bn J
JacquoF. N rr Stewart D. Ebneter, Director Division of Reactor Safety d
Enclosure:
As Stated 8609240367 860918 go\\
PDR ADOCK 05000277 G
PDR OFFICIAL RECORD COPY GRAY 9/9/868 - 0001.0.0 g \\
09/17/86 i
Philadelphia Electric Co.
2 cc w/ enc 1:
R. S. Fleischmann, Manager, Peach Bottom Atomic Power Station John S. Kemper, Vice President, Engineering and Research Troy B. Conner, Jr., Esquire W. H. Hirst, Director, Joint Generation Projects Department, Atlantic Electric G. Leitch, Superintendent Nuclear Generation Division Eugene J. Bradley, Esquire, Assistant General Counsel (Without Report)
Raymond L. Hovis, Esquire Thotas Magette, Power Plant Siting, Nuclear Evaluations (Without Report)
W. M. Alden, Engineer in Charge, Licensing Section Public Document Room (PDR) local Public Document Room (LPDR)
Nuclear Safety Information Center (NSIC)
NRC Resident Inspector Commonwealth of Pennsylvania bec w/ encl:
Region I Docket Room (with concurrences)
Management Assistant, DRMA (w/o encl)
Section Chief, DRP Robert J. Bores, DRSS J. Durr J. Wiggins H. Gray 1
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EXAMINATION CF A SECTION OF LONCITUDINALLY WELDED AUSTENITIC STAINLESS STEEL FIFE FOR TRANSVERSE LINEAR INDICATIONS K. V. Cook, B. E. Foster, and C. M. Goodwin We were requested by E. O. Woolridge [ Division of Engineering Technology, U.S. Nuclear Regulatory Commission (NRC)] to investigate radiographic indications noted in a section of steel pipe for Peach Botton Unit 2.
A section of type 316 stainless steel pipe containing radiographic indications (associated with the weld) was received f rom the NRC Region I representative.
Examination of the accompanying copies of radiographic film revealed the indications noted as " transverse molecular alignment indications" in a memorandum from J. Durr to C. Serpan dated May 28, 1985.
The sample dimensions were 33.1 mm (1.33 in.) thick, 50.8 mm (2 in.)
wide, and 280 mm (11 in.) long. The sample was radiographed through the 33.1-mm thickness dimension at energies of 230, 265, and 300 kVcp.
In all three exposures the noted indications were clearly evident.
In addition, the sample was radiographed with the X-ray beam at a 7* angle to the incident surface. Again the indications were c1carly evident with little or no change. We achieved a penetrameter sensitivity of 0.8%.
The predominant indications were parallel and approximately 9.4 mm (0.375 in.)
long with weaker images being slightly over 15.7 mm (0.625 in.) long.
After initial radiography, the pipe section was hand dressed to a 812-mm (32 uin.) finish on all four sides of the weld region, macroetched with aqua regia, and photographed.
Figure 1 shows transverse, top (outside diameter), and bottom (inside diameter) surf aces. The macroetch reveals the columnar dendritic solidification structure typical of austenitic stainless steel welds. The highly reflective stripe in the centerline of the top view [ Fig. 1(b)] is f rom the essentially vertical growth experienced at the trailing edge of the weld puddle, accentuated by the high heat input undoubtedly used in the pipe manufacture.
The ferrite content of the weld fusion zone was mapped using a Twin-City Testing Ferritescope.
The gas tungsten-arc welded root region showed a ferrite number (FN) of 0.5, and the major portion of the submerged-arc fill passes showed 2.5 FN.
A central region of the fill passes and a narrow zone on the top surf ace chowed 0.5 FN.
2 All four weldment surf aces were examined for surf ace flaws with a Zyglo fluorescent penetrant technique in accordance with MET-NDT-4.
The specific technique used Magnaflux ZL-22A penetrant, ZE-3 emulsifier, and ZP-4B dry developer.
The emulsifier time was approximately 2.5 min.
No significant indications were detected.
There were a few indications in the heat-af fected zone areas and in some areas within the pipe base metal; however, swabs dampened with alcohol successfully wiped them away (we commonly use this procedure to evaluate penetrant indications).
We also examined the weld with both 2.25-and 1-MHz ultrasonic pulse-echo shear-wave contacc methods. A slot with a depth of 10% of the wall thickness was used to calibrate the tests. This notch, machined on the inner surf ace, was placed near the heat-affected zone parallel to the veld. The notch (selected in accordance with Article III,Section II, of the ASME Code) was easily detected by either frequency inspection from the base material (type 316L stainless steel pipe).
However, the notch was not detectable when the sound beam (either frequency) was required to pass through the weldment. Thus, it appears that the nominal 45' shear-wave setup in the pipe may not be totally adequate for the weldsent.
Nevertheless, both the 2.25-and 1.0-MHz tests were applied.
No indications were detected in either the axial or circumferential direction with the 1-MHz unit. Typical noiselike signals (seen in most austenitic welds that we have examined) were noted with the 2.25-MHz. test, but they did not correspond to the radiographic indications. Thus, the radiographic indications did not cause ultraconic indicatioos that could inhibit satisf actory in-service inspection with the shear-wave technique.
We sectioned through the radiographic indication area, obtaining a slice approximately 8.1 mm (0.325 in.) thick. The cut surfaces of this alice and the remaining 3/.5-am-thick (1.5-in.) section were hand dressed to a 812-mm (32-pin.) finish, macroetched with aqua regia, and
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The two cut surf aceu were examined for flaws with the same f luorescent penetrant technique used prior to cutting.
The results were nearly identical in that a few minor indications in the heat-aff ected zone l
area were also detected that were wiped away successfully with an i
a lcohol-dampened swab.
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3 The 37.5-mm-thick (1.5-in.) section was radiographed using a 1921r isotopic source. The radiation passed through the 33.1-mm (1.33-in.)
thickness (weld crown to root).
The indications detected with X rays were not evident.
However, the radiographic sensitivity was not as good with the isotopic source.
The thinner slice was radiographed through the 8.1-am (0.325-in.)
thickness using X rays. The radiographic Laage was quite similar to that of the surface when observed visually.
Figure 2 shows 500x magnification micrographs of the transverse section, including the top (outside diameter), center, and bottom (inside diameter) regions, and Fig. 3 shows the fusion line (a) and heat-af f ected zone (b).
The microstructure is typical of material that has been solution annealed af ter welding.
The heat-af fected zone is wide and coarse grained, and the fusion zone confirms the ferrite variations noted previously.
Reductions in ferrite levels in the center of welds have been noted in the literature for other processes, and are usually attributed to changes in solidification growth rate. The residual ferrite in the fusion zone is highly agglomerated, and there is evidence of sigma phase nucleated at ferrite islands. The entire weldment microstructure is coarse, reflecting the high heat input welding procedure, and indicating a rigorous solution annealing treatment.
None of these metallographic observations are considered abnormal.
A section of the weld that was approximately 6 mm thick was electron-beam welded to matching end tabs and successfully passed the 180*
side bend. test.
Subsequent dye penetrant testing showed zero indications in the weld area. The outer surf ace of the bend specimen is shown in Fig. 4.
The volumetric location of the transverse linear indications (noted radiographically) appears to be in the outer one-third (toward the crown) of the weld region.
Specifically, we can conclude the following:
1.
Radiographic indications were clearly evident in the pipe weld specimen with the X-ray beam at two different incident angles, discounting the possibility of diffraction effects.
2.
Macroetching revealed a coarse weld structure typical of high heat input weldments in austenitic stainless steels.
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3.
Ferrite content of the weld fusion zone varied from 0.5 FN at the root, top surf ace, and central region to 2.5 FN for the major portion of the submerged-arc fill passes. This variation in the distribution of a second phase of dif ferent composition and density is a possible contributor to the observed X-ray effects.
4.
Fluorescent penetrant testing of all four weldsent surf aces showed no significant indications.
5.
Ultrasonic testing detected no indications in either the axial or circumferential directions.
6.
Radiography using a 1921r isotopic source did not reveal the indicstions detected with I rays.
7.
None of the metallographic observations of the weld microstructure are considered abnormal.
8.
The weldsent passed a 180* side bend test with no unusual indications.
9.
None of the above conclusions should be anticipated to have any adverse ef fect on the fitness for service of the subject pipe.
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