ML20235U412

Metallurgical Investigation of Recorded Ultrasonic Testing Indications at Pressurizer Surge Line Welds at Trojan Nuclear Generating Station

ML20235U412
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	09/30/1988
From:	Pezze C, Rao G WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML20235U400	List: ML20235U397 ML20235U412 ML20235U428
References
WCAP-11986, NUDOCS 8903090190
Download: ML20235U412 (33)

Text

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WESTINGHOUSE CLASS 31 t WC' AP-11986 METALLURGICAL INVESTIGATION OF THE RECORDED UT INDICATIONS AT .THE PRESSURIZER SURGE LINE WELDS AT- '

TROJAN NUCLEAR GENERATING STATION

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GUTTI RA0 CINDY PEZZE SEPTEMBER 1988 t Approved by:

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T. R. Hager, Manager MetallurgicaIandNDEAnalysis Work Performed Under Shop Order PPYJ-138 Althsugh information contained in this report is non proprietary, no distribution shall be made outside Westinghouse or its licensees without

. customer's approval.

WESTINGHOUSE ELECTRIC CORPORATION Power Systems Division P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 8903090190 390228 f hDR ADOCK 05000344 PNU f.

' 326Fs/D9294810

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TABLE OF CONTENTS Section ~ Title Page

1.0 INTRODUCTION

1-1 2.0 EXAMINATIONS AND TESTS 2-1 2.1 Surface Examinations 2 2.2 Sectioning Procedure 2-1

- 2.3 Meta 11ographic Examinations 2-2 2.4 Hardness Measurements 2 2.5 Tensile Tests 2-3 3.0 RESULTS AND DISCUSSION 3-1

4.0 CONCLUSION

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LIST OF FIGURES Figure Title

!2-1 Sectioning procedure employed on the horizontal pipe to elbow shop weld

!2-2 -Sectioning procedure employed on the vertical pipe to albow field weld l2-3, ID surface appearance of the horizontal pipe to albow i

weld joint in the as-received condition (0.6x) 2-4 ID surface appearance of the horizontal pipe to albow

- weld joint in the as-received condition (0.6x) /

2-5 ID surface appearance of the vertical pipe to elbow weld joint in the.as-received condition (0.4x)

2-6 Scanning electron micrographs illustrating the as-

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received ID surface condition of the weld at the

horizontal pipe to elbow joint 2-7 Meta 11ography results illustrating the microstructure

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of the horizontal pipe to elbow weld at S1A3A location (figure 2.1) 2-8 Details of the microstructure at the weld interface at locations marked E and F in figure 2-7.

2-9 Details of weld microstructure at locations marked

'C' and 'D' in figure 2-7 2-10 Details of weld microstructure at locations 'A' and 'B' in figure 2-7 wummo $$

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LIST OF FIGURES (cont.)

,i Figure Title 2-11 Meta 11ography results illustrating the weld micro-structure of the horizontal pipe to elbow joint at

-location SIA2 (figure 2-1) 2-12 Details of weld interface microstructure at locations ~

A and B, figure 2-11 2-13 Details of weld interface microstructure at-locations C and D, figure 2-17 14 Details of weld microstructure at locations marked E, F.and G, figure 2-11 2-15 Meta 11ography results illustrating the weld micro- ,

structure of the horizontal pipe to elbow weld joint at locations S183A.(figure 2-1) .

2-16 Meta 11ography results illustrating the details of the microstructure of the weld interface at locations A and B in figure 2-15 2-17 Meta 11ography results illustrating the details of the microstructure of the weld interface at locations C and D in figure 2-15 2-18 Meta 11ography results illustrating the grain size and microstructure of the elbow material ns.ame io iij

s LIST OF TABLES Title Page Table Summary of Hardness Measurement Results of the Elbow 4-8 2.1 Material Summary of Room Temperature Tensile Test Results of 4-9 2.2 the Elbow Material . .

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SECTION 1.0 INTRODUCTION The pressurizer surge line is designed as a flow path between the Reactor Coolant Loop (RCL) and the pressurizer for the pressure control of the Reactor Coolant System (RCS). Portland General Electric (PGE) began monitoring the pressurizer surge line in 1982 for whip restraint contact in the Trojan Power Plant. Over the next six outages contact was observed on some pressurizer surge line whip restraints. An engineering consulting firm, IMPELL performed an extensive piping evaluation of the Trojan pressurizer surge line and concluded that the root cause of surge line movements is plastic deformation l of the piping due to thermal stratification. In order to assure the integrity of the line, it was recommended that PGE perform a volumetric inspection of all pressurizer surge line circumferential welds during the next refueling

-outage.

-During the 1988 inservice examination of the Trojan pressurizer surge line the NDE vendor using ultrasonic techniques identified two circumferential welds with apparent defects. Radiographic examinations failed to confirm the presence of these defects. The two suspect areas were then removed and submitted to Westinghouse for metallurgical investigation.

The suspect areas are a field weld between a horizontal pipe section and the elbow and a shop weld between the elbow and a vertical pipe section. Per the specifications, the horizontal and vertical sections of pipe are 14 inch schedule 160 fabricated from SA-376 TP 316 material and the elbow is 14 inch schedule 160 fabricated from SA-182 F 316 material. A gas tungsten arc weld (GTAW) process with a Type 308 stainless steel weld wire was used for both welds. Weld records indicate that the horizontal pipe to elbow field weld was l welded, cut out, rewelded and repair welded.

The purpose of the metallurgical investigation performed by Westinghouse was tti provide a clear definition of the morphology, orientation, depth and

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" distribution of the cracking, establish the mechanism and the cause(s) of the cracking, and to develop information that would be helpful in taking correc-tive actions. As the evaluations progressed, no cracks were identified. To further identify the metallurgical conditions that gave raise to the recorded indications, additional UT tests are in progress on controlled samples. The findings of these evaluations will be summarized in a separate Westinghouse report. The current report summarizes the findings of the metallurgical investigation performed on the two circumferential welds removed from the Trojan pressurizer surge line. The evaluations included visual examinations, dry sectioning, light optical microphotography, light optical metallography, hardness measurements, and mechanical property tests.

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SECTION 2.0 3 -

EXAMINATIONS AND TESTS l

-l 2.1 Surface Examinations 3 The inside diameter (ID) and outside diameter (OD) surface conditions of the two elbow welds were examined in the as-received condition for evidence of cracking deposits and surface attack. The ID surface examinations were conducted following sectioning of the pipe. longitudinally along the intradose to extradose diameter of the elbow as indiidated in figures 2.1 and 2.2 The results of the surface examinations are illustrated in figures 2.3 through 2.6.

2.2 Sectioning Procedure .

-Figure 2.1 is a schematic illustration of the sectioning sequence used on the horizontal pipe and elbow section submitted for evalu3 tion. Initially a transverse section through the elbow was made to isolate the suspect field

• i weld.(piece S1). Two longitudinal cuts separated piece S1 in two halves (S1A _

and SIB) providing access for ID surface examination. The ID surface was then decontaminated and subjected to supplemental ultrasonic examination (piece SIB 1). Additional section was made on S1B1 to obtain metallographic sample S1Bl. The decontaminated ultrasonic sample S1B1 was shipped in two pieces (S182A and S182B) for PGE for metallographic and UT evaluations respectively.

' Figure 2.2 is a schematic illustration of the sectioning sequence used on he elbow and vertical pipe section submitted for evaluation. Two transverse sections were made to isolate the suspect shop weld (piece S4). Two longitudinal custs separated piece S4 in two halves (S4A and S4B) providing access to the ID. The final longitudinal cuts were made to provide metallographic samples (pieces 54B4 and S4B1). .

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e 2.3 Meta 11ooraphic Examinations Meta 11ographic examinations were conducted on sections S1A3A, SIB 3A, S1A2, and SIB 1B from the horizontal pipe to elbow field weld and on sections S4B4 and S4B1 from the elbow to vertical pipe shop weld. The metallographic samples ,

, were mounted, polished and etched in a solution containing acetic acid, nitric 3 acid, hydrochloric acid and glyceron. The samples were examined under the light microscope in both the as polished and etched condition. The results are illustrated in figures 2.7 through 2.18.

2.4 Hardness Measurements Rockwell B hardness measurements wore performed on the elbow base metal. The measurements were taken on the cross sections at midwall on S1A2A and S183A, and on the OD surface away from the weld on S1B3A. The results are presented ,

in table 2.1.

2~. 4 Tensile Tests Tensile tests were conducted on the elbow material to examine its confirmance to the specification requirements. Circumferentially oriented 0.505 ASTM bar samples were machined from the elbow and tested at room temperature. The results are summarized in table 2.2.

O" w i e Sa 2-2

SECTION 3.0 RESULTS AND DISCUSSION The outside diameter surface examinations in the as-received condition did not reveal any evidence of cracking, surface deposits, or other degradation. The

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sectioning procedure employed on the elbow welds to gain access to the inside diameter surface and to obtain the test specimens for various examinations are ,

illustrated in figures 2.1 and 2.2. The inside diameter surface examination results are illustrated in figures 2.3 through 2.6. The ID surface cor.dition '

as can be seen here did not show any evidence of cracking or surface attack.

The results of tne metallographic examination are illustrated in figures 2.7 through 2.18. Figure 2.7 illustrates the weld overlay and microstructure of the horizontal pipe to elbow (shop) weld at S2A3A location (figure 2.1). As can be seen, no evidence of weld defects or cracking is apparent here. Higher inagnification micrographs illustrating the details of the micro-structure. at selected areas in the weld metal and at the weld to base metal interface (marked 'A' through 'F') are illustrated in figures 2.8 through 2.10.

MetallograpMc examination results of the weld metal to base metal interface areas at the ID surface are illustrated in figures 2.8 and 2.9 (marked by areas 'E' and 'D' respectively). Microstructure at region 'E' (figure 2.8) here showed the presence of a shallow (approximately 0.0004 in, deep) defect with the appearance of a crack initiation at the weld metal to base metal interface. No evidence of any other cracking was seen at the ID surface. The micrographs in figure 2.10 illustrate the appearance of microporosity seen in '

the weld metal at areas 'A' and 'B'. The microporosity seen here is con-sidered normal for these welds. Figures 2.11 and 2.15 illustrate the weld microstructure of the shop weld at two other locations identified as S1A2 and l S1B3A in figure 2.1.

Details of the microstructure seen at the two weld l sections are illustrated at M7 er magnification in figures 2.12 through 2.14, and in figures 2.15 through 2.18, respectively. The microstructure '

illustrated here failed to confirm the presence of any cracking or defects at tfieselocations. Metallographic examination results of sections S4B1 and S4B2 taken from the elbow to vertical oipe field weld suggested similar findings.

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'The overall results of the surface examinations and metallographic examina-

- tions thus showed no evidence of cracking or defects that could have given raise to the circumferential indications recorded during the inservice examination. }

During the metallographic examinations, it was observed that the elbow material grain size near these weld regions was larger than normally expected. The typical microstructure seen in the elbow material is illustrated in figure 2.18. The grain size here corresponded to an ASTM grain size number of nearly 'O'. To insure that the elbow material met the mechani-cal property requirements hardness and tensile property measurements were made on the elbow material. The results of the Rockwell 'B' hardness survey of the elbow material are summarized in table 2.1. The hardness values suggested slightly lower than expected tensile strength value for the material. The results of the tensile tests are summarized in table 2.2. The tensile strength values of the two samples tested corresponded to 71.29 ksi and 81.48 ksi respectively. Although these values suggested a 10 ksi differential, the

.cverage value (76 ksi) corresponded to the expected tensile value for the material as per the specification requirements.

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SECTION 4.0~

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i CONCLUSIONS

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Based on the overall results of the evaluations it is concluded that the shop

" and field welds of the surge line elbow did not contain any cracking or

. defects that could have contributed to the recorded indications. Although the elbow material exhibited larger than expected grain size, the mechanical property measurements showed that it meets the specification requirements.

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Table 2.1 .

RESULTS OF HARDNESS MEASUREMENTS OF ELB0W MATERIAL Sample

• Hardness, Rockwell B

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S1A2A 70.2 S1B3A 69.7 S183A(OD) 80.9 ,

ONote: Hardness values listed are average of five measurements.

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SUMMARY

OF THE ROOM TEMPERATURE TENSILE TEST RESULTS OF THE ELBOW MATERIAL l (Circumferential1y Oriented Specimens) l Ultimate 0.2% Yield Tensile . -

5pecimen Dia. Strength Strength  %  % Reduction .s 1.D. No. (in) (ksi) (ksi) Elongation in Area -

1 0.505 35.95 71.29 65.9 78.3 2 0.505 36.45 81.48 72.3 80.7 {

ASTM A 182, 30 75 30.0 50.0 -

F 316 (min.) (min.) (min.) (min.) -

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