ML20081F574

Steam Generator/Pressurizer Preservice Exam

ML20081F574
Person / Time
Site:	Byron
Issue date:	10/27/1983
From:	COMMONWEALTH EDISON CO.
To:
Shared Package
ML20081F554	List: ML20081F549 ML20081F574
References
7490N, NUDOCS 8311030134
Download: ML20081F574 (63)

Text

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ATTACHMENT A Byron Unit 1 Steam Generator / Pressurizer Preservice Examination Contents Section 1:

".ntroduction and Background Section 2:

Initial Evaluation Section 3:

Detailed Evaluation Section 4:

Summary of Recommendations Section 5:

Fracture Evaluation of Indications in Pressurizer Section 6:

Repair of Indications in Pressurizer Section 7:

Overall Conclusions and Recommendations 7490N 8311030134 831027

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i BYRON UNIT 1 STEAM GENERATOR / PRESSURIZER PRESERVICE EXAMINATION SECTION 1 INTRODUCTION AND BACKGROUND Section XI of the ASME Boiler and Pressure Vessel Code requires a preservice exami-nation of pressure -retaining welds in nuclear power plant pressurizers and steam

. generators prior to initial plant startup. To meet this requirement, Commonwealth Edison Company contracted with EBASCO Services, Inc. to perform the required i

nondestructive tests on the Byron Unit 1 nuclear power station steam generators and 4

pressurizer. The examinations were conducted in accordance with the 1977 edition of the ASME Code through to the Summer 1977 addenda.

Several indications which exceeded the recording amplitude were noted during the ultrasonic examination of the steam generators and pressurizer. Commonwealth 4

Edison Company contracted with Westinghouse Electric Corporation to assist in the evaluation and analysis of the test data obtained.in the preservice examination.

The following sections of this report will describe the tests that were performed, the analysis of test data and the reconsnended actions that should be taken as a result of the analysis-,

SECTION 2 INITIAL EVALUATION Based on an initial evaluation of the preservice examination data, the following j

seven areas were identified as requiring further evaluation before final disposition was determined:

EBASCO Deficiency Report Component

-Weld-Location PSI-D-139 Loop 1 Steam Gen. Stub-Barrel-to-Lower Shell 113" CCW Cire. Weld PSI D-144 Loop 1 Steam Gen.

Stub-Barrel-to-Lower Shell 93" CCW

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Circ. Weld l

PSI D-147 Loop 2 Steam Gen. Closure Cire. Weld 951" CW l

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.EBASCO Deficiency Report Component Weld Location PSI D-160 Loop 2 Steam Gen. Closure Cire. Weld 69-3/4" CCW PSI D-148 Loop 2 Steam Gen.

Closure Cire. Weld 113" CCW PSI D-140 Pressurizer Lower Head-to-Shell Circ.

106" to 135" Weld CW PSI D-163 Pressurizer Lower Head-to-Shell Cire.

1401" CW Weld At the time the initial evaluation was completed, it was impossible to perform supplementary nondestructive examinations due to the scheduled hot functional tests. Upon completion of hot functional testing, the following additional nondestructive examinations were performed:

(1) Visual examination of the pressurizer and loop 2 steam generator inside diameter surface.

(2) Ultrasonic examination of the pressurizer and loop 2 steam generator from the inside diameter surface.

(3) Magnetic particle examination of the loop 2 steam generator inside diameter surface.

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(4) Radiographic examination of the pressurizer and loop 2 steam generator.

It was not 70ssible to perform supplementary nondestructive examinations on the L

loop 1 steam generator due to the inaccessibility of the inside diameter surface I

in the area of interest.

SECTION 3 l

A.

DETAILED EVALUATION OF LOOP 1 STEAM GENERATOR INDICATIONS 1.

INDICATION AT 113" CCW POSITION (DEFICIENCY REPORT PSI D-139)

a. Location of Indication The indication at the 113" CCW position in the loop 1 steam generator is located

'in the stub barrel-to-lower shell circumferential weld. Based on ultrasonic

test data obtained when examining from the outside diameter surface, the indication is at or near the inside diameter surface. The projected location and orientation of the reflector is illustrated in Figure 1.

b. 0.D. Ultrasonic Test Results The area around the 113" CCW location in the loop 1 steam generator stub barrel-to-lower shell circumferential weld was examined from the outside diameter surface on 3/18/82, 4/12/83, and 8/5/83. The official preservice examination was conducted on 3/18/82 using ASME Code techniques. The indication in question was detected by both 45* and 60* examinations from both above and below the weld.

However, onl'y the 45 examinations produced a signal of recordable amplitude. A reexamination of the area in question was performed on 4/12/83 and 8/5/83 to determine if the original data could be repeated. Only 45 tests were conducted during the reexaminations. The following is a summary of the data obtained from all the examinations:

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Date of Test 3/18/82 3/18/82 3/18/82 3/18/82 Test Angle 45*

45*

60*

60 Transducer Position Above Weld Below Weld Above Weld Below Weld Indication Amplitude 51% DAC 58% DAC 23% DAC 21% DAC Length 1.63" 0.75" Spot Spot Minimum Depth 2.62" 3.67" Maximum Depth 3.04" 4.04" Through-Wall 0.42" 0.37" Spot Spot a/1 0.26 0.25 N/A N/A a/t 0.134 0.058 N/A N/A Allowable a/t 0.033 0.041 N/A N/A Date of Test 4/12/83 4/12/83 8/5/83 8/5/83 Test Angle 45 45 45 45*

Transducer Position Above Weld

.Below Weld Above Weld Below Weld Indication Amplitude 74% DAC 75% DAC 88% DAC 67% DAC Length 1.19" 0.63" 1.75" 1.0"

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Minimum Depth 2.65" 3.68" 2.62" 3.76" Maximum Depth 2.85" 3.84" 3.03" 4.08" Thro 4gh-Wall 0.20" 0.16" 0.58" 0.32" a/l.

0.08 0.13" 0.33 0.16 a/t.

0.031 0.025"

.0.18" O.050 Allowable a/t 0.028 0.031" 0.037 0.027 b

c. Evaluation and Recommendation The fabrication radiographs.were reviewed to determine if there was a radiographic indication that would correlate with the ultrasonic indication. However, the radiographs of the area in question did not contain any indications that would t

match the ultrasonic reflector. Also, the lack of adequate access to the inside diameter surface prevented the performance of any meaningful supplementary nondestructive examinations.

Based on the results obtained during the ultrasonic examinations from the outside

' diameter surface, it.is recomended that a repair be performed to remove the

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. ultrasonic reflector. The indication of the 113" CCW position is only 20" from

. another rejectable reflector described in Deficiency Report PSI D-144. The lack of meaningful supplementary. data that~would provide evidence of a nondetrimental condition makes the removal of the questionable reflector logical.

4 2.

INDICATION AT 93" CCW POSITION (DEFICIENCY REPORT PSI D-144)

a. Location of Indication l

l The. indication at the 93" CCW position in the loop 1 steam generator is located in the stub barrel-to-lower shell circumferential weld.

Based on the ultrasonic test data obtained when examining from the outside diameter surface, the indication extends from the inside diameter surface in a planar direction. The through-wall 1

l dimension varies with test angle, transducer location (above or below the weld),

l and date.of examination. The projected location and orientation of the reflector f

is illustrated in Figure 2.

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b. 0.D. Ultrasonic Test Results The preservice examination of the area around the 93" CCW location in the loop 1 steam generator stub barrel-to-lower-shell circumferential weld was performed on 3/18/82 using standard ASME Code techniques. The indication in question was detected at above recording level amplitudes during both 45* and 60' examinations from both above and below the weld. A reexamination on 8/5/83 again produced recordable indications from 45* and 60* tests from above and below the weld. The following is a summary of the data obtained from the various examinations:

Date of Test 3/18/83 3/18/83 3/18/83 3/18/83 Test Angle 45*

45*

60*

63 Transducer Position Above Weld Below Weld Above Weld Below Weld Indication Amplitude 240% DAC 177% DAC 77% DAC 120% DAC Length 2.938" 2.688" 1.938" 2.125" Minimum Depth 2.93" 3.25" 2.65" 3.24" Maximum Depth 3.30" 3.78" 3.35" 4.24" Through-Wall 0.37" 0.53" 0.70" 1.00" a/l 0.09 0.22 0.28 0.49 a/t 0.084 0.18 0.172 0.325 Allowable a/t 0.022 0.031 0.035 0.037 Date of Test 8/5/83 8/5/83 8/5/83 8/5/83 Test Angle 45 45*

60*

60 Transducer. Position Above Weld Below Weld Above Weld Below Weld Indication Amplitude 273% DAC 240% DAC 88% DAC 100% DAC Length 3.188" 2.938" 1.188" 1.625" Minimum Depth 2.88" 3.39" 2.59" 3.47" Maximum Depth 3.35" 3.87" 3.41" 4.23" Through-Wall 0.47" 0.67" 0.61" 1.03" a/l 0.15 0.22 0.51 0.63 a/t 0.147 0.209 0.190 0.322 Allowable a/t 0.026 0.030 0.037 0.037

Examinations with a 0 transducer did not produce any evidence that an inside diameter surface condition or geometry were causing the reflector detected during the preservice examination. The reflector is thin, planar, and parallel to the weld axis.

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Evaluation and Recommendations -

A review of the fabrication radiographs indicate a repair was made in the area where the ultrasonic indication occurs. However, there were no radiographic indications that would correlate with the ultrasonic indication. The lack of adequate access to the inside diameter surface prevented the use of any meaningful supplementary nondestructive testing.

Based on the results obtained during the ultrasonic examination from the outside diameter surface, it is recommended that a repair be performed to remove the

' ultrasonic reflector.

It is very unusual to obtain indications with large amplitudes from both sides of the weld with both 45* and 60 test angles. All eight examinations produced data which exceed ASME Code,Section XI criteria.

Also, the indication is only 20 inches from a similar reflector reported in Deficiency Report PSI D-139.

i B.

DETAILED EVALUATION OF LOOP 2 STEAM GENERATOR INDICATIONS 1.

INDICATION AT 951" CW POSITION (DEFICIENCY REPORT PSI D-147) a.

Location of Indication The indication at the 951" CW position in the loop 2 steam generator closure circumferential weld is a subsurface reflector located approximately 2-3/4 inches from the outside diameter surface.

The projected location and orientation of the reflector is shown in Figure 3.

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0.D. Ultrasonic Test Results During the preservice $xamination of the loop 2 steain generator, a questionable indication was recorded at the 951 CW location of the closure circumferential weld.- A reexamination.on 3/4/83 indicated that the reflector was still present.

The following is a summary of the data found during the examinations from the outside diameter surface.

Date of Test 3/22/82 3/22/82 3/22/82 8/4/83 Test Angle 45*

60*

60*

45?,

Transducer Position Above Weld Above Weld Below Weld Alove Weld Indication Amplitude 80% DAC 38% DAC 13% DAC 85% DAC Length 1.438" Spot Spot 0.5" Minimum Depth 2.62" 2.62" Maximum Depth 2.93" 2.98" Through-Wall 0.31" Spot Spot 0.36" a/1 0.11 N/A N/A 0.36 a/t-0.039 N/A N/A

' 0.045 Allowable a/t 0.029 N/A N/A 0.053 c.

I.D. Ultrasonic Test Results A' supplementary ultrasonic examination from the inside diameter surface was performed on 8/3/83. One indication was noted at the 951" CW location when conducting a 45*

examination from below the weld. The maximum amplitude of the indication was 26% DAC l

which is below ASME Code Section XI sizing criteria..The length when sizing from

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where the. indication first appears to where the indication disappears was 3/8".

There was no measurable. through-wall dimension. The indication was located 1.413" from the. inside diameter surface.

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d. Visual Examination Results

.The inside diameter surface in the area where the indication was obtained was smooth and even. Since the indication is-subsurface, it would not be logical to attribute the reflection to a surface condition or component geometry.

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Magnetic Particle Examination Results The area where the indication was obtained was magnetic particle examined from the inside' diameter surface using a Parker Research A. C. yoke. As expected, no magnetic particle indications were obtained.

f.

Radiographic Examination Results The area where the ultrasonic indication was noted was radiographically examined using a 48 curie Cobalt 60 source. The key test parameters are presented in tabular form in this section and included in the text in subsequent sections.

The key test parameters were:

FF Distance - 29" Penetrameter - 50 Sensitivity - 2T or better Exposure Time - 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, 55 minutes Film - (4) 7" x 17" Kodak M film per-shot Shots - #1 - 3" above weld centerline (6* angle)

1. 2 - straight at weld centerline

1. 3 - 3" below weld centerline (6* angle)

The finished radiographs were reviewed by Commonwealth Edison, EBASCO, and Westinghouse personnel. There was considerable diffe.rence in the interpretation results. At various times, radiographs'were evaluated as indication-free, containing a faint slag line, containing a lack-of-fusion indication, and containing a transverse crack indication.

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Evaluation and Recommendation Due to the inability of the various radiographic readers to reach a uniform interpretation that the radiographs are acceptable to ASME Code criteria, it is y

recommended that the area in question be repaired to remove the indication.

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2.

INDICATION AT 69-3/4" CCW POSITION (DEFICIENCY REPORT PSI D-160) a.

Location of Indication The indication at the 69-3/4" CCW position in the loop 2 steam generator closure weld is located at or near the inside diameter surface. The location and orientation of the reflector is shown in Figure 4.

b.

0.D. Ultrasonic Test Results The original preservice examination was performed on 3/22/82. Although indications were obtained from both 45* and 60* tests from both sides of the weld, only the 45*

examination from below the weld was of an amplitude requiring sizing. A reexamination from below the weld using a 45* transducer was performed on 8/5/83.

The following is a summary of the data obtained from ultrasonic examinations conducted from the outside diameter surface:

Date of Test 3/22/82.

3/22/82 3/22/82 3/22/82 8/5/83 Test Angle 45*

45*

60*

60*

45 Transducer Position Below Weld Above Weld Below Weld Above Weld Below Weld Indication Amplitude 100% DAC 43% DAC 48% DAC 29% DAC 100% DAC Length 1.1" Spot Spot Spot 1.3125" Minimum Depth 3.35" 3.77" Maximum Depth 4.09' 4.19" Through-Wall 0.65" Spot Spot Spot 0.23" a/l 0.61 N/A N/A N/A 0.18" a/t 0.16 N/A N/A N/A 0.058 Allowable a/t 0.037 N/A N/A N/A 0.027 c.

I.D. Ultrasonic Test Results Two 45* indications and one 60 indication were obtained at the 69-3/4" CCW location when testing from the inside diameter surface. The two 45* indications each had amplitudes of 100% DAC and depths from the inside diameter surface of 0.5".

One of the 45* indications had a length of 15/16" and the second indication had a length of 9/16". The 60* indication had a depth from the inside diameter of 0.4", a length

of 2-1/2", and a maximum amplitude ~of 80% DAC. The through-wall dimension of all three indications was approximately 0.2".

d.

Visual Examination Results A visual examination of the inside diameter surface indicated there is no surface condition or component geometry that would cause the ultrasonic indications,

o. Magnetic Particle Test Results The area where the indication was obtained was magnetic particle examined from the inside diameter surface using a Parker Research A. C. yoke. No indications were obtained indicating the ultrasonic reflectors are subsurface.

f.

Radiographic Test Results A radiographic examination was' performed in the area where ultrasonic indications were obtained. A 48-1/2 curie Cobalt 60 source was used. The FF distance was 29 inches and exposure time was two hours.

Four 7" x 17" Kodak M film were used for each shot. One shot was made straight at the weld centerline; a second shot iwas taken 3 inches above the weld centerline (6' angle); and a third shot was taken 3 inches below the weld centerline (6' angle). The radiographs had a 2T sensitivity or better.

i All radiographs were read by Commonwealth Edison, EBASCO, and Westinghouse personnel.

'There appeared to be faint slag lines in the area where ultrasonic indications were obtained.

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Evaluation and Recommendation 4

. Based on the ultrasonic and radiographic test results, it is recommended that the area i-be repaired to remove the indications. The supplementary nondestructive examinations support the original preservice examination data which does not meet ASME Code Section XI criteria.

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3.

INDICATION AT 113" CCW POSITION (DEFICIENCY REPORT PSI D-148) a.

Location of Indication The indication at the 113" CCW location in the loop 2 steam generator closure weld is in-the weld at or near the inside diameter surface. The location and orientation of the projected reflector is illustrated in Figure 5.

b.

0.0. Ultrasonic Test Results The original preservice ultrasonic examination Trom the outside diameter surface was conducted on 3/22/82.

Indications were obtained with both the 45 and 60*

tests from both above and below the weld. However, only the tests from above the weld produced indications which exceeded the 50% DAC sizing level established in the ASME Code. A validation reexamination was performed on 8/3/83 and 8/4/83.

Indications which exceeded the 50% DAC sizing level were obtained with both the 45' and 60* tests from above end below the weld. The following is a summary of the data from ultrasonic examinations conducted from the outside diameter surface:

Date of Test 3/22/82 3/22/82 3/22/82 3/22/82 Test Angle 45' 45' 60 60 Transducer Position Below Weld Above Weld Below Weld Above Weld Indication Amplitude 43% DAC 147% DAC 50% DAC 100% DAC Length Spot 1.6" Spot 1.3" Minimum Depth 4.04" 4.29" Maximum Depth 4.45" 5.18" Through-Wall Spot 0.41" Spot 0.89" a/l N/A 0.28" N/A 0.91 a/t N/A 0.103 N/A 0.295 Allowable a/t N/A 0.035 N/A 0.037

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Date of Test 8/3/83 8/3/83 8/4/83 8/4/83 Test Angle 45*

45*

60*

60*

Transducer Position Below Weld Above Weld Below Weld Above Weld Indication Amplitude 82% DAC 157% DAC 80% DAC 180% DAC Length 0.75" 0.937" 0.56" 1.937" Minimum Depth 3.97" 4.08" 3.53" 4.41" Maximum Depth 4.29" 4.53" 4.29" 5.29" Through-Wall 0.29" 0.53" 0.29" 1.29" a/l 0.39 0.57 0.52 0.67 a/t 0.073 0.133 0.073 0.32 Allowable a/t 0.037 0.037 0.037 0.037 c.

I.D. Ultrasonic Test Results When testing from the inside diameter surface, two indications were obtained during the' 45* examination and three indications were obtained during the 60* examination.

The following is a summary of the most pertinent data obtained from the inside diameter examinations:

Test Angle 45*

45*

60*

60*

60 Transducer Position Below Weld Above Weld Below Weld Above Weld Above Weld Indication Amplitude 30% DAC 200% DAC 20% DAC 200% DAC 100% DAC Length Spot 0.44" Spot 0.81" 0.44" Through-Wall Spot 0.47" Spot 1.12" 1.0" Distance from I.D.

.7"

.6"

.5"

.4"

.4" Surface

d. Visual Examination Results A visual examination of the inside diameter surface indicated there is no surface condition or component geometry that could cause the ultrasonic indications.

e. Magnetic Particle Test-Results T N area where ultrasonic indications were obtained was magnetic particle examined from the inside diameter surface using a Parker Research A.C. yoke. No indications

,were obtained which supports the I.D. ultrasonic data that indicates the reflector (s) are subsurface, t

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f. Radiographic Test Results A radiographic examination was performed in the area where ultrasonic indications had been obtained. A 48-1/2 curie Cobalt 60 source was used. The FF distance was 29 inches and exposure time,was two hours.

Four 7" x 17" Kodak M films were placed on the inside diameter surface for each shot. One shot was made straight at the weld centerline; a second shot was taken three inches above the weld centerline (6* angle); and a third shot was taken three inches below the centerline (6* angle). The radiographs had a 2T sensitivity or better.

All radiographs were read by Commonwealth Edison, EBASCO, and Westinghouse personnel.

The only indications noted were possible slag lines near the inside diameter surface.

g. Evaluation and Recommendation Based on the ultrasonic and radiographic test results, it is recommended that the area be repaired to remove the indications. The supplementary nondestructive examinations support the original preservice examination data which does not meet ASME Code Section XI criteria.

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C.

DETAILED EVALUATION OF PRESSURIZER INDICATIONS 1.

INDICATIONS BETWEEN 106" T0135" CW POSITION (DEFICIENCY REPORT PSI D-140)

a. Location of Indications The preservice examination ultrasonic indications in the pressurizer are in the lower head-to-lower shell circumferential weld (Figure 6). The outside diameter surface contour of the lower head-to-lower shell weld is at best marginally-acceptable when attempting to make quantitative ultrasonic measurements. As shown in Figure 7, the theoretical contour contains tapers and abrupt changes which make prediction of actual test angles difficult. The actual contours of the Byron Unit 1 pressurizer is much more irregular than the theoretical contours.

The area in which the ultrasonic transducer must scan contains humps and valleys as well as the tapers and abrupt changes. The distortion of the sound wave is most noticeable when using the 60* transducer due to the need to scan further away from the weld centerline and reflectors.

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Because of the diffic.ulties in knowing the actual test angle when conducting an ultrasonic test from the outside diameter surface, test data from the inside diameter tests are considered more accurate.

As will be discussed in detail later, the indica'tions between the 106" to 135" CW position are located in the

- weld at a depth of approximately 1 inch from the inside diameter surface.

b.

0.D. Ultrasonic Test Results The-indications in question were detected when conducting 60* examinations from the outside diameter surface. When tested on 8/3/82 as part of the official preservice examination, three indications which were acceptable to ASME Code Section XI criteria were recorded.

During a reexamination on 4/6/83, three indications were recorded.- Two of the three indications exceeded ASME Code Section XI requirements.

The ' test data from the seccnd examination differed greatly from that obtained from the first examination.

The most likely cause for the wide variation is'the difficulty in obtaining accurate quantitative data due to the irregular outside diameter contours.

The following is a summary of the data

,obtained from the two examinations:

Date of Test 8/3/82 8/3/82 8/3/82 Test Angle 60*

60' 60' Transducer Position 107" CW 118" CW 135" CW Below Weld Below Weld Below Weld Indication Amplitude 100% DAC 115% DAC 60% DAC Length 1.25" 2.75" 1.5 Minimum Depth 2.48" 2.52" 2.44" Maximum Depth 2.59" 2.67" 2.63" Through-Wall 0.11 0.15" 0.19" a/l 0.044 0.027 0.063 a/t 0.013 0.018 0.023 Allowable a/t 0.028 0.026 0.028 queuL A '

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Date of Test 4/6/83 4/6/83 4/6/83 Test Angle 60*

60*

60*

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06-3/P G Transducer Position Above Weld Below Weld Below Weld Indication Amplitude 120% DAC 350% DAC 220% DAC Length 1.0" 4.0" 0.625" Minimum Depth 3.04" 2.96" 2.96" Maximum Depth 3.48" 3.26" 3.11" Through-Wall 0.44 0.30 0.15" a/l 0.22 0.04 0.12

'.018 a/t 0.053 0.036 0

Allowable a/t 0.038 0.026 0.030

c. I.D. Ultrasonic Test Results A supplemental ultrasonic examination was performed from the inside diameter surface to gather data that would assist in characts;rizing the reflectors. Two 45 indications were recorded in the area between 116" CW to 137" CW. One indication located at the 116-1/4" CW position required an increase in test system gain of 14 dB above the reference level in order to obtain a 60% full screen height indication. The second indication located at the 1366" CW position required an increase in test system gain of 6 dB above the reference level to obtain a 60% full screen height indication.

The following is a summary of key sizing data obtained

.at the increased gain settings described in the previous sentences:

l Date of Test 8/3/83 8/3/83 Test Angle 45 45*

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Indication Location 1161" CW 136t" CW Increase in Gain 14 dB 6 dB Length 1-1/2"

• l-1/8"

• Depth from I.D. Surface N1" s1" could not obtain through-wall data due to surface condition noise Through-Wall at high gain settings.

• - Sized'to 50% DAC levels at increased gain setting.

d. Visual Test Results A visual examination of the inside diameter surface did not reveal any unusual surface conditions or, component geometry that could explain the reflectors obtained during ultrasonic examinations.

It was noted that there were several intermittent patches of manual cladding that projected above the shop automatic cladding. However, the closest any patch came to a recorded indication was approximately seven inches. Also, the depth of the indications (approximately one inch from I.D. surface) would rule out any surface condition as the cause of the reflectors.

e. Radiographic Test Results A radiographic examination was performed of the area where indications exceeding ASME Code Section XI criteria (118" CW) were recorded. A 48 curie Cobalt 60 source was used. The FF distance was 24 inches and exposure time was one hour, five minutes.

Four 7" x 17" Kodak M films were placed on the inside diameter surface for each exposure. One shot was made straight at the weld centerline; a second shot was taken three inches above the weld centerline (6* angle); and a third shot was taken three inches below the weld centerline (6* angle). Most of the radiographs had a sensitivity of IT.

All radiographs were read by Commonwealth Edison, EBASCO, and Westinghouse personnel.

Two of the interpreters evaluated the radiographs as being indication-free. The third interpreter indicated he saw two very faint tight lines which he interpreted as being slag.

f. Evaluation and Recommendations During the original preservice examination conducted on August 3, 1982, all the indications between the 106" CW and 135" CW locations were acceptable to ASME Code,Section XI criteria. The reexamination conducted on April 6, 1983 produced data that was significantly different thak that obtained during the preservice j

examination. The indication recorded at the 135" CW position during the preservice l

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4 examination was not recorded during the April 1983 examination. Only one indication was recorded at the 118" CW position during the preservice examination while two indications were recorded during the 1983 examination.

The variations in length, depth, and through-wall dimensions far exceed normal, ultrasonic tolerances. The most likely cause of the lack of repeatability is the 0.D. surface contour which inakes quantitative analysis difficult.

The ultrasonic examination from the inside diameter, the visual examination, and i

the radiographic examination did not produce indications which exceed ASME Code Section XI-requirements. Based on the difficulty in obtaining meaningful data from the ' utside dia'neter surface and the acceptable supporting data from o

complementary nondestructive examinations, it is recommended that no repairs be made in the pressurizer between the 106" CW to 135" CW positions.

2.

INDICATION AT 140i" CW POSITION (DEFICIENCY REPORT PSI D-163)

a.. Location of Indicatioq The indication at the 140i" CW position in the pressurizer is located in the lower

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head-to-lower shell circumferential weld (Figure 6). The surface contour of the outside diameter surface is very irregular and the comments contained in the discussion of indications between 106" CW and 135" CW also apply to the indication at the 1401" CW position.

b. 0.D. Ultrasonic Test Results A suninary of the data obtained during the preservice examination from the outside diameter surface is as follows:-

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Date of Test 8/3/82 4/8/83 Test Angle No recordable indication 45*

Transducer Position Below Weld Indication Amplitude 123% DAC Length 3.188"

F Minimum Depth 2.65" Maximum Depth 3.24" Through-Wall 0.59" a/l 0.092 a/t 0.074 Allowable a/t 0.029 c.

I.D. Ultrasonic Test Results A supplemental ultrasonic examination was performed from the inside diameter surface to gather data that could assist in characterizing the reflec. tor. A 45' indication was recorded at the 140" CW location.

It was necessary to increase the test system gain 6 dB above the reference level to obtain a 40%

full screen height indication. The following is a summary of key sizing data obtained at the increased gain setting:

1 Date of Test 8/3/83 Test Angle 45 Indication Locatfan 140" CW Increase in Gain 6 dB Depth from I.D. surface sla Through-Wall could not obtain through-wall data due to surface condition noise at the high gain setting Length 2-1/8" d.

Visual Test Results A visual examination of the inside diameter surface did not reveal any unusual surface conditions or component geometry that could explain the reflector obtained during the ultrasonic examination.

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Radiographic Test Results 1

l A radiographic examination was performed of the area around ths 140" CW pgsition.

y A 48 curie Cobalt 60 source was used.' The FF distance was 25 inches and the exposure time was one hour, twelve minutes. Four 7" x 17" Kodak M filmkware used for each exposure. Oneshotwasmadestraightattheweldcenterline;Isecond '

i shot was taken three inches above the weld centerline ~ (6* angl,e); a third shot was taken three inches below the weld centerline (6' angle). Most of the radiographs had a sensitivity of 1T.

All radiographs were read by Commonwealth Edison, EBASCO, and Westinghouse personnel. Two of the interpreters evaluated the radiographs as being' indication-free. The third reader indicated he saw one very faint indication indicative of tight slag.

'l f.

Evaluation and Recommendations During the original preservice examination, conducted in August 1982, EBASCO (the preservice examination subcontractor) did not submit a Deficiency Report for any indications in the 140" CW location. The indication recorded during the reexamination on April 8,1983 is the only data which does not meet' ASME Code,Section XI criteria.- The extremely irregular outside diameter surface in the area makes the accuracy of the data suspect.

The ultrasonic examination from the inside diameter, the visual examination, and the radiographic examination did not produce data which exceeds ASME Code,Section XI

' criteria. Based on the difficulty in obtaining meaningful data from the outside diameter surface and the acceptable supporting data from the complementary non-destructive examinations, it is recommended that no repairs be made in the.

pressurizer lower head-to-lower shell weld at the 140" CW position.

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SECTION 4

SUMMARY

OF RECOMMENDATIONS / CONCLUSIONS The following is a summary of recommendations for the seven areas covered by the Deficiency Reports in question:

Deficiency Report Component Weld Location Recommendation PSI D-140 Pressurizer Lower Head-to 106" CW to Do not' repair Lower Shell 135" CW PSI D-163 Pressurizer Lower Head-to-1401" CW Do not repair Lower Shell PSI D-147 Loop 2 Steam Closure 951" CW Repair Generator PSI D-160 Loop 2 Steam Closure 69-3/4" CCW Repair Generator PSI D-148 Loop 2 Steam Closure 113" CCW Repair Generator PSI D-139 Loop 1 Steam Stub Barrel-113" CCW Repair Generator to-Lower Shell PSI-D-144 Loop 1 Steam Stub Barrel-93" CCW Repair Generator to-Lower Shell

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SECTION 5

_ FRACTURE EVALUATION OF INDICATIONS IN PRESSURIZER 1

-INTRODUCTION The preservice inspection of the pressurizer revealed indications at three I

different locations in the lower head to lower shell circumferential weld, as ' discussed earlier in this ' report. Two of th'ese indications exceeded the allowable standards of Sectio'n XI.U) However, the size of these two indi-cations was not confirmed by additional examinations, and so they are not considered to require repair.

For'added information on the severity of these indications and' their impact on the integrity of the pressurizer, a fracture evaluation was performed.

For conservatism, the largest of the indications was evaluated, and the

-methods and criteria of Appendix A of Section XI were used.

It is recog-nized here that preservice indications xhicn exceed the acceptance stand-ards cannot be justified by fracture evaluation according to Code rules.

In this case, however, the indications have not been confirmed as exceeding the standards, and the fracture evaluation is provided for infor= tion purposes.

The indication chosen for evaluation was at the 140.5" CW position (deficiency report PSI-0-163).

This indication has a through wall dimension of 0.59 inches and is located about one inch from the inside surface of the pressurizer, as shown in Figure 5-1.

The proximity of the indication to the inside surface of the pressurizer determines whether it must be considered as a surface or embedded. flaw in the fracture evaluation. The indication will be embedded if the following requirement'is satisfied:

k( [1-4(]

(1) where e = eccentricity, defined in Figure 5-1 t = wall thickness a = flaw half depth t-

The largest indication dim;nsions measured in inspection of this region were

".

• used:

a = 0.295 t = 4.17 e = 0.86 D '"

2-.g = 0.412 t

'l - 4f = 0.717 Therefore, since the inequality of equation (1) is satisfied, the flaw may be considered embedded.

5-2 METHOD OF EVALUATION The indication was evaluated according to the crtieria set forth in Section

. XI of the ASME Code, article IWB 3600 [1].

The fracture methods used followed the approach suggested in Appendix A of Section XI, and the material properties were taken directly from the Appendix A reference properties.

There are two sets of flaw acceptance criteri in articia IWS 3600:

1.

Acceptance criteria based on f1'aw size (IWB 3611)

I 2.

Acceptance criteria based on stress intensity factor (IWB 3612)

The criteria based on' applied stress intensity -factor were used for the evalua-tion.

Namely, (1)

For normal, upset, and test conditions:

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K<

(2) l' 7~E0 l

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-where K is the maximum applied stress intensity for emergency / faulted conditions y

for the flaw size af which is the final crack flaw size calculated by crack

. growth analysis.

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corresponding crack tip temperature. A reference K curve is found in Ia Appendix A of Section XI.

(2)

For emergency & faulted conditions K c Kg<

(3) where K is the maximum applied stress intensity for emergency / faulted conditions g

for the flaw size a which is the final flaw size calculated by f

crack growth analysis.

K is the available fracture toughness based on fracture initiation for Ic the corresponding crack tip temperature. A reference K curve is found Ic in Appendix A of Section XI.

In order to complete a fracture evaluation per the above criteria, three analyses are necessary.

First a fatigue crack growth analysis must be performed to determine the amount of growth expected for the indication, if it were a crack.

This crack size is then used to calculate the value of the applied stress intensity factor for the most governing nomal, upset and test condition, and separately the most governing emergency and faulted condition.

Each of these calculations will be discussed in detail in the sections to follow.

5-3 FATIGUE CRACK GROWTH ANALYSIS The goal of this analysis is to predict the growth of the indication during the service of the pressurizer until the next inspection, a period which has been taken as 10 years. A separate calculation was also carried out for the full operating life of the plant, 40 years.

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The analysis procedure involves assuming th'at the indication is a flaw and predicting the growth of that flaw due to an imposed series of loading transients. The input required for a fatigue crack growth analysis is basically the information necessary to calculate the parameter K which y

depends on crack and structure geometry and the range of applied stresses in the area where the crack exists. Once K is calculated, the growth y

due to that particular stress cycle can be calculated by the fatigue crack growth reference law given in Section XI Appendix A.

This increment of growth is then added to the original crack size, and the analysis proceeds to the next transient. The procedure is continued in this manner until all the transients known to occur in the period of evaluation have been analyzed.

The transients considered in the analysis are all the design transients con-tained in the vessel equipment specification. These transients are spread equally over the design lifetime of the vessel, with the exception that the preoperational tests are considered first. The transients for the model 84D pressurizer for Byron Unit 1 are listed in Table 5-1, along with the number of occurrences specified for the 40 year design life.

The thermal transients were conservatively lumped, as shown in Table 5-1, with the number of occurrences for each lumped transient being the total of all the occurrences for the individual transients combined.

The stresses due to each of these transients were calculated using a detailed finite element model of the lower shell to lower head weld region. The cal-culated, axial stresses (which act perpendicular to the plane of the flaw) were then linearized through the wall thickness of the vessel, to enable a conservative calculation of the range of stress intensity factor, AK 7

for each transient.

The stress intensity factor expression provided in Appendix A of Section XI-was used directly in the anal' sis. The equation for the K ' expression is:

y y

K =,/

[cm "m + "B "B3 y

' ~

where a a flaw half depth (Fig. 5-1) o,, cB = membrane and bending stresses, from linearization Q = flaw shape parameter, from Appendix A, Fig. A3300-1 M,, 4 = membrane and bending correction factors from Appendix A, Figs. A3300-2 and A3300-4 The range of s' tress intensity factor AK required for fatigue crack growth

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y calculations is then determinid directly from evaluation of K at the maxi-y mum and minimum stress point in a given cycle. The crack growth can then be calculated using the crack growth reference law for embedded flaws in ferritic steels. This reference law is shown in Appendix A, Figure A4300-1, and repeated in Figure 5-2.

The crack growth rate reference curve for air environments is a single curve, with growth rate being only a function of applied AK.

This curve has the equation:

3.726 (5) fa = (0.0267 x 10-3) g dN I

da

where, dN = crack growth rate, micro-inches / cycle K = stress intensity factor range, ksi/in y

= (K

-KImin)

Imax The strdsses used in the crack growth analysis are tabulated in Table 5-2, and the results.of the' analysis are shown in Table 5-3.

As may be seen from the table, the crack growth during the entire design life is insignificant.

The crack grows from a = 0.295 inches to a = 0.303 inches in ten years, and f

to af = 0.33 inches in the entire design life.

The fatigue crack growth was assumed to be self-similar, so the length of the flaw after growth becomes 3.24 ir.ches.* These crack dimensions were then used in the determination of allowable flaw depths for nomal and faulted

. conditions, to be discussed in the next section. The growth of the flaw does not change its treatment as an embedded flaw, since the inequality of equation (1) is still satisfied.

• Af ter 10 years.

5-4 ALLOWABLE FLAW SIZE DETERMINATION To determine the allowable flaw size for the loca~ tion of interest in the pressurizer, the fracture toughness of the material and the applied stress intensity factor or driving force for the flaw must be calculated.

The criteria for allowable flaw size are then:

K"I

'Ky < /10 for normal, upset, and test conditions KIc Ky</2 for emergency and faulted conditions The fracture toughness of the Byron I pressurizer material, both Kla.and Ky were determined based on reference curves provided in Appendix A of Section XI, which are reproduced in Figure 5-3.

These curves were originally intended for application only to prssure vessel steels with yield strength less than 50 ksi, but extensive testing on pressurizer steel and welds have verified the appli-cability of the reference curves for these materials [3]. The Byron Unit 1 pressurizer bottom head and lower shell are fabricated of SA533 Grade A Class 2 plate material.

l The reference toughness curves are given in tenns of the RT for the NDT material, which is a parameter detennined from Charpy and drop weight tests. The maximum allowable RT for the pressurizer material is 60 F, NDT and the maximum for the weld material is 10*F.

Since the caterial is near the weld base metal interface, the higher RT was used in the NOT analysis for conservatism.

The fracture toughness is defined by the following equations:

K, = 26.8 + 1.233 exp[0.0145 (T - RTNDT + 160F)]

g K

= 33.2 + 2.806 exp[0.02 U - RTNDT + 100F)]

p)

Ic where K, and KIc are in ksi/in and T and RTNDT are in *F.

g

___r,

Once the fracture toughness has been detemined as a function of metal

' ~

temperature, the most governing transients must be identified. Through a datailed invcstigation of the system design transients and their effect on this region 'of the pressurizer, the following transients were selected:

Governing hormal, Upset and Test Conditions:

Hydrotest Heatup/Cooldown Governing Emergency and Faulted Condition:

General Condition 1 The hydrotest is nominally the worst of the nomal, upset and test condi-tions, because it is conducted at a relatively low temperature (minimum 150*F). However, it is a preoperational test, and is unlikely to be utilized once the plant starts up. The next most governing transient is the heatup and cooldown event, which involves a 195 F range in temperature initiating from a pressurizer pressure of 118 psi and temperature of 340*F.

The governing faulted condition, gene El condition 1,is an umbrella for the themal transients seen by the pressurizer due to large LOCA, large stea'm line break, feedwater line break, and steam generator tube rupture.

The pressurizer vessel is assumed to be initially void of water but with the metal temperature at 635*F, and this is filled solid with water entering at a temperature of 212*F. After temperature equilibrium is reached, the pressurizer is cooled down at a rate of 200 F/ hour to a temperature of 140 F.

Pressurizer spray is assumed to be initiated for 3 minutes, spraying 212 F water at design flow rates into' the vessel.

The_ axial stress distribution through the pressurizer vessel wall was deter-mined as a function of time for each of these transients from a detailed finite element analysis.

The stress distributions along with the tempera-ture distributions for the critical time in each transient considered are listed in Table 5-4.

~.. -. _,

This stress infonnation along with the final flaw size detemined from the fatigue crack growth analysis were used to calculate the applied stress in-tensity factor X for each transient. The stress intensity factor, K,

7 g

varies' around the periphery of the flaw, and was calculated using solution of Shah and Kobayashi [4]. A detailed study by Lee and Bamford [5] recently confirmed the applicability of Shah -and Kobayshi's work to the case.of an embedded flaw in a cylindrical vessel. This stress intensity factor epres-sion is more accurate than the expression available from SU, tion XI Appendix A (equation 4) because it utilizes a cubic polynomial curve fit to represent the stress distribution accurately, rather than a linearization. This more accurate treatment is necessary to detennine the allowable flaw size for the governing transients.

The applied stress intensity factor around the per-iphery of the flaw for each of the transients analyzed is plotted in Figure 5-4, for the flaw size is as predicted from crack growth analysis at ten years of operation. A second plot of stress intensity factor around the periphery of the' flaw for a predicted end-of-life flaw size is presented

-in Figure 5-4.

The allcwable flaw size is then determined from the ratio of applied stress intensity factor to the applicable fragture toughness value, obtained from the temperature of the metal at the loiiat' ion of the flaw.

The appropriate ratios for each of the transients analyzed are discussed in the next section.

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5-5 RESULTS AND CONCLUSIONS A flaw evaluation analysis has been carried out for the largest of any of the indications discovered in the lower shell to lower head weld in the pressurizer, Results show that the indication meets the acceptance criteria of Section XI of the ASME Code throughout the plant lifetime, as may be seen in t,he. detailed comrarisons below.

A fatigue' crack growth analysis was carried out which showed that the indi-cation would grow only slightly during the entire plant lifetime.

Flaw evaluation analyses were completed at two different times in the plant life-time,10 years (8 EFPY) and end-of-life, 40 years (32 EFPY). The detailed results will be presented below:

Evaluation at 10 years a

= 0.30 from fatigue crack grcwth analysis, Table 5-3 f

f

= 3.24 f

(1) For Primary Hydrotest Temperature = 156F (see discussion below for source)

Stresses - see Table 5-4 Maximum Ky (see Figure 5-4) = 22.3 ksi/in Kla (from equation 6) = 77.27 ksi/in Ia = 24.43 > 22.3 'ksi /in

/i0 (2)

For Heatup/Cooldown Temperature at peak stress time = 474F Stresses - see Table 5-4 Maximum Ky (see Figure 5-4) = 11.9 ksi/in Kla (from equation 6) = 200 ksi/in K

Ia = 63.24 11.9 ksi/in Ai

~...-

(3)

For General Condition #1 Temperature at peak stress time = 377F Stresses - see Table 5-4 Maximum Ky (see Figure 5-4) = 31.3 ksi/in K;c (from equation 7) = 200 ksi/in KIc 31.3 ksi/in

= 141

/i' Evaluation at End of Life a

= 0.33 from fatigue crack growth analysis, Table 5-3 '

f f

= 3.56 f

-(1) For Primary Hydrotest Temperature = 181F (see discussion below for source)

Stresses see Table 5-4 Maximum Ky (Figure 5-5) = 23.4 ksi/in Kyg (from equation 6) = 99.3 ksi/in J

K Ia

= 31.40

> 23.4 ksi/in M

(2) For Reatup/Cooldown Temperature at peak stress time = 474F Stresses - see Table 5-4 Maximum Ky (see Figure 5-5) = 12.7 ksi/in Kla (from equation 6) = 200 ksi/in KIa

= 63.24 > 12.7 ksi/in E

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f E.

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^(3) For, Gentral Condition. #1,r c

1,

t I

Temperature at peak stress time =' 474F.

't F

St'resses - see Table'd-4 Maximum Ky (see Figuie 5f6) = 33.5 ksi/in KIc (Equation 7) = 200 ksi/in K

~

^

Ic

/2 33.5 ksi/in

'/

= 141 The above comparisons clearly snow the indication to be acceptable throughout

~

the plant lifetime. The most limiting comparison is for the primary hydrotest, where the test temperature is detennined based on the limiting value of RT NDT for the primary system. At the beginning of life the test temperature will be 150F, because of the requirement that the test. temperature must be greater i

than or equal to RTNDT + 90F for, the closure'nead region of the vessel. As time passes the hydrotest temperature will increase due ' o the increase in RT t

NDT in the reactor vessel beltline. At 10 years, or'8 effective full power years, the hydrotest temperature would be at least RTNDT + 60F, d ere RTNDT is deter-mine at.the quarter-thickness location in the reactor vessel beltline. At the end of life for the plant, this quarter-thickness RT value would be NDT 121F, so the hydrotest temperature would,ba at least 181F. Since the hydro-test temperature increases with time,'and there is no irradiation damage in the pressurizer, the toughness of the pressurizer steel during the hydrotest increases with the length. of service of the plant. This in turn increases the margin present in the flaw evaluation process, as can be seen from the above calculations.

There are a number of conservatisms included' Iri the present analysis, and so the. indication would be shown acceptable by an even wider margin if these were included.

First, the governing condition in the evaluation is the hydrotest transient, which is. unlikely to occurjafter the plant goes into operation. Considering the next must governing transient the margin is much larger.

,d i

f f

i

Tho fatigue crack growth analysis utilized transients which were lump:d under a few governing conditions. This resulted in a conservatively higher stress level for each of the conditions which were lumped. This is particularly important for the thermal transient #2, where the relatively mild steady. state fluctuations are lumped with more severe transients. This transient results in 84 percent of the total crack growth calculated.

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5.6 REFERENCES

1.

ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components",1980 Edition.

2.

"Model D Series 84 Pressurizer Stress Report Fracture Mechanics Analysis",

^'estinghouse Electric Corp. Nuclear Equipment Divisions, Tampa, Fla. Re-

=

port No. WNET-130 volume 1, September 1976.

3.

Logsdon, W. A., Begley, J. A., and Gottshall, C. L. " Dynamic Fracture Toughness of ASME SA508 CL 2a & ASME SA533 Gr A C12 Base and Heat Affected Zone Material and Applicable Weld Metals" Westinghouse Electric Corp. WCAP 9292, March 1978.

4.

Shah, R. C. and Kobayashi, A.

S., " Stress Intensity Factor for an Elliptical Crack Under Arbitrary Loading", Engineering Fracture Mechanics vol. 3,1971,.

pp. 71-96.

5.

Lee, Y. S. and Bamford, W. H., " Stress Intensity Factor Solutions for a Longitudinal Buried Elliptical Flaw in a Cylinder under Arbitrary Loads" presented at ASME Pressure Vessel and Piping Conference, Portland, Oregon, June 1983, Paper 83-PVP-92.

l.

TAdur F-l TRANSIENTS USED IN FATIGUE CRACK GROWTH ANALYSIS Occurrences in Design Life Primary Hydrotest 10 Primary Leak Test, Turbine Roll 220 Secondary Leak Test 200 Heatup/Cooldown 600 OBE 400 Thermal Transient' #1 27,790 Unit load / Unload (18300 Step Load Increase (2000 Feedwater Cycling (4000

' Loop Out of Service (140 Loss of Power (80 Reactor Trip B (160 Reactor Trip C (10)

Inadvertent Startup of Inactive Loop (20 Inadvertent SI Actuation (80 Thermal Transient #2 3,217,000 Step Load Decrease (2000)

Large Step Decrease (200)

Loop Out of Service (80 Loss of Power (40 Partial Loss of Flow (80 Control Rod Drop (80 6

Steady State Fluctuations (3.15 x 10 )

Loss of Load (Thennal Transient #3) 80 Thermal Transient #4 260 Reactor Trip A (230)

' Inadvertent RCS Depressurization (30)

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TABLE 5-2

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STRESSES USED IN $4TIGUE CRACK GROWTH ANALYSIS i

Transient Cycles Maximum Axial Stress Minimum Axial Stress Inside Surf.

Outside Surf.

Inside Surf.

Uutside IUFF (ksi)

(ksi)

(ksi)

(ksi)

Primary Hydro 10 23.650 35.644 0.000 0.000 Heatup/Cooldown 600 32.275

-25.098 0.000 0.000 OBE 400 12.903 42.149 15.785 32.024 Thermal Trans. #1 24790 8.444

-6.624 11.326 33.414 Thermal Trans. #2 3217000 19.559 29.021 11.326 33.414 Loss of Load 80 18.375 32.251 11.326 33.414 Thermal Trans. #4 260 37.488 13.977 11.326 33.414 Primary Leak Test 220 19.040 28.699 0.000 0.000 Secondary Leak Test 200 2.666

4. 01 8 0.000 0.000 5:

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TABLE 5-3 RESULTS OF FATIGUE CRACK GROWTH ANALYSIS Initial Crack Crack Dimension After half, width, 10 years 20 years 30 years 40 years

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a = 0.295 0.30 0.31 0.32 0.33 Initial Crack

length, L = 3.188*

3.24 3.35 3.46 3.56 9

1 5:

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TABLE 5-4 STRESSES USED IN ALLOWABLE FLAW SIZE CALCULATIONS 1

Primary Hydrotest Distance from ID Axial Stress Temperature Surface, + wall thickness (ksi)

(*F) 0.0 23.65 150*F 0.10 23.78 150

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0.30 24.07 150 0.50 24.71 150 0.70 26.21 150 0.90 32.50 150 1.0 35.64 150 Heatup - Cooldown 1

0.0 32.28 474*F O.10 24 /17.'

474 0.30 9.75 474 0.50

-1.98 474 0.70

-10.89 474 0.90

-20.36 474 1.0

-25.10 474 General Condition 1 0.0 85.84 234.9*F 0.10 65.84 310.2 0.30 25.81 443.8 0.50

-5.96 539.9 0.70

-29.09 596.2 0.90

-53.17 622.0 1.0

-65.21 633.3 m

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Figure 5-1 Description of Indication Analyzed, Byron Unit 1 Pressurizer b

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m.

gen 700 600 500 400 300 200 100--

90

[~

80

~ 70 wd so SUS SURFACE FLAWS-U 50 (Air Environment) s g 40

= (.0267X10-') AK 3#8' i

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t 2

3 4

5 6 78910 20 30 40 50 60 70 8090 00

• STRESS INTENSITY FACTOR MANGE, aX (KSI T l g

Figure 5.2 Upper Bound Fatigue Crack Gro'wth Data for Reactor Vessel Steels

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0213e:1 14

220 200 18 0 l

i 16 0 14 0 z

I g

12 0 KIa E

i Na yH 10 0 x x o

3O m

j o

F 80 e'..

go 3 H sx y

60 ac 40 -

20 -

RTNOT a

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-50

+M

+E

+I 0

( T-RTNDT) F j

I I

Fig. 5.3 l.ower Bound K,a and K i

SA-508 Class 3SteeIE Test Data for SA-533 Grade B Class 1, SA-508 Class 2, and i

i 1

l

s N' I-

• l 3

5 I

I I

Semi-minor axis:

Semi-major axis: 0.3* T = 4.17, CASE I

1. 6 ',' n = 1. 225"

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1.25 -

m 2.

1.

m i-A O

5;j p-

't

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• GENERALCONDIT10ft;_/

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PRIllARY HYDR 0

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n- ~ ~

w s-s

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s, L

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c

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s s

p'

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g w

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ss

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flGURE 5-4 Results of Stress Intensity Factor Calculation, Indication in Byron linit 1 Pressurizer Shell Weld (Case t )

Q 1-l

.g Semi-major axis 1.78

CASE II l 225, Semi-minor axis 0.33 '

T = 4.17 in., n = 1.225 in.

. L 1.78 GENERAL CONDITION r'

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[

l

,e 1

e

/

0.32 as

/

PRIfMRY HYDR 0 y

u

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~

I O

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FIGURE S-5 Results of Stress Intensity Factor Calculation Indication in Byron Unit i Pressurizer Shell Weld (Case II)

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...,.[ s SECTION 6 REPAIR OF INDICATIONS IN PRESSURIZER (IF REQUIRED)

A.

Background

A pre-service ultrasonic inspection of the pressurizer (PZR) Bottom Head to shell circumferential weld reported two questionable indications.

The indications are approximately 20 inches apart and estimated to be at a depth of iT or deeper, located from the 0.0 surface. The length of the indications are approximately 3 to 4 inches in length.

B.

Repair Options (1) Repair From Vessel I.D. Surface Considerations were given to performing a weld repair from the I.D.

surface, based on the indication locations being within the inner IT thickness of the weld. This approach is not recommended for the following reasons:

Access to back side of weld is limited due to heater arrangement.

Removal of some heaters may be required to improve welder access.

Welding preheat will affect welder efficiency during I.D.

weld repair.

Weld repair from the vessel I.D. is judged to be inefficient and impractical.

(2) Repair From. Vessel 0.D. Surface Employing the Temper Bead Weld Technique Weld repair can best be accomplished from the 0.0. surface of the weld joint. The following, however, must be considered if a weld repair is made to the Pressurizer from the 0.D. surface employing the temper bend technique:

The repair cavities will be approximately 6" long by a depth greater than iT.

Defect sizing and location by U.T. is not accurate and additional grinding may be required if other indications are observed either visually or by surface NDE methods. This may alter the repair cavity.

- There is a potential for opening additional undetected indications during weld repair in the highly restrained weld repair cavity.

,./

The residual stresses resulting from the weld repair may be more detrimental than the effects of the original questionable indications if not removed.

(3)' Repair from Vessel OD Surface Employing Conventional Weld Repair Conventional weld repair would require a post weld heat treatment (PWHT) at 10250F + 250F of a band of 2 inches above and below the weld repair arounii the entire vessel. The problems associated with this include the following:

1. To avoid sensitization of the instrument nozzles, these nozzles would have to be removed during PWHT and replaced after PWHT.

2. A redesign of the instrument nozzle to pressurizer shell weld will have to be developed, analyzed and qualified to allow attachment from the OD.

3. The heater support plates will have to be unbolted and all tack welds removed in order for the plate to be free to move.

4. Ensure that the stainless steel heater well temperatures do not exceed 8000F by keeping the pressurizer insulated and cooled.

This would avoid sensitizing the stainless steel.

It should be noted that a preliminary thermal evaluation of the assumed PWHT conditions indicates that the heater well temperature will remain remain below C400F. This evaluation was performed using very conservative heat transfer assumptions. Relaxing some of these assumptions would in all probability show that the heater wells would remain below 8000F.

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• SECTION 7 OVERALL CONCLUSIONS AND RECOMMENDATIONS 1.

Repair the five rejectable and questionable areas in the steam generators.

2.

Do not repair the questionable areas in the pressurizer. The ultrasonic examination from the inside diameter, the visual examination and the radiographic examination did not produce indications which exceed ASME Code Section XI requirements. Obtaining any meaningful data from the outside diameter surface was very difficult to obtain and the supporting data from the complementary non-destructive examinations were found to be acceptable.

3.

The results of a fracture evaluation of the questiontble indications in the pressurizer (which assumed that these questionable indications were indeed real) clearly show them to be acceptable throughout the plant lifetime by a wide margin band upon conservative assumptions.

4.

In the event that it is deemed desirable to repair the pressurizer indications, the repair should be made employing the temper beads weld technique from the outside surface of the vessel. This would avoid any potential sensitization of the heater wells and eliminate the necessity to remove and replace tha instrument nozzles from the OD.

h_u...