ML20209H281

Forwards Summary of Util Ultrasonic Exam of Cast Stainless Component Welds at Byron Unit 2 & Braidwood Unit 1,per KA Ainger Re Insp of Steel Component Welds W/Relief Requests.Procedure NDT-C-38 Also Encl

ML20209H281
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	09/02/1986
From:	Miosi A COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20209H286	List: ML20209H281 ML20209H288
References
2061K, NUDOCS 8609150203
Download: ML20209H281 (31)

Text

- . . . - _ - - - _ . . -.

- W A , One First Nabonel Plaza, Checa00, Illinois

• Address Reply 17. Post Omco Box 767 Chece00. Illinois 80000 - 0767 1

> September 2, 1986 1

Mr. Harold R. Denton U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, DC. 20555

Subject:

Byron Station Unit 2

, Braidwood Station Unit 1 Inspection of Cast Stainless Steel Component Welds with Relief Requests NRC Docket Nos. 50-455 and 50-456

Reference:

June 25, 1986 K.A. Ainger letter to H.R. Denton

Dear Mr. Denton:

Enclosed is the report (Attachment A) which summarizes I efforts by Commonwealth Edison to perform meaningful ultrasonic I examinations of cast stainless steel component welds at Byron and Braidwood Stations. This report includes discussions of an ultrasonic examination procedure developed specifically for these welds, the training of inspection personnel and the results of preservice examinations performed at Byron Unit 2 and Braidwood Unit l 1 with the new procedure. Also, enclosed are the relief requests that document where the preservice examinations did not meet ASME Section XI requirements. Approval of these relief requests by the l Nuclear Regulatory ca==i==ian (NDri is required prior to fuel load

, at the respective sites.

Following discussions with NRC and Electric Power Research Institute (EPRI) personnel in November, 1985, Commonwealth Edison's

! System Materials Analysis Department (SMAD) implemented a program to develop an ultrasonic examination procedure capable of detecting large flaws in the cast stainless steel welds at Byron and l Braidwood. Previous attempts at examining these welds were 4

unsuccessful due to severe attenuation, scattering and re-direction i

of sound energy by cast material microstructure. To reduce the

. severity of these problems during the development of the new procedure, SMAD utilized state of the art ultrasonic techniques made known to them by EPRI. The new procedure was optimized by

] fine-tuning the EPRI techniques to the material properties of the Byron and Braidwood welds.

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Development of the examination procedure involved the manufacturing of curved calibration standards from a cast stainless steel elbow with attenuation properties comparable to the Byron /Braidwood cast material. Refracted longitudinal wave transducers capable of detecting the calibration holes and notches in the calibration blocks were then procured. A full-size cast stainless steel weld mockup was also obtained from the Marble Hill plant to simulate in-plant conditions.

Verification of the new procedure's capabilities was performed on the Marble Hill mockup. Circumferential and axial notches were cut into the inner Thesediameter (I.D.) surface of the notches were detected during mockup to simulate weld flaws.

examination from the cast side of the mockup. The procedure was also tested on four weld samples borrowed from the Westinghouse Pressurized Water Reactor Owners Group. These samples contained mechanically induced and thermal fatigue cracks. Only one crack in the samples could not be detected. Identification of this crack was prevented by outer diameter surface geometry of the weld sample.

Based on these test results, SMAD concluded that the procedure can identify large flaws in the counterbore region of the cast stainless steel welds. The capabilities of the new procedure were demonstrated to Nuclear Reactor Regulation and NRC Region III personnel at the Braidwood site on June 26, 1986.

Preservice inspections of the cast component welds at Byron Unit 2 and Braidwood Unit 1 have been completed. Tne cast side of these welds were recently examined using the new procedure. The non-cast side of the welds were examined previously by other ultrasonic techniques. Preservice inspections at Byron were performed by Ebasco Services, Incorporated, the preservice inspection contractor. Inspections at Braidwood were performed by Commonwealth Edicen Company (CECO) perennnal. Prior to examining the cast side of the welds, inspection personnel demonstrated their ability to detect notches and cracks in the weld mockup and weld samples to the satisfaction of the CECO corporate Level III examiner.

l Examinations made on the cast side of the welds include circumferential and axial angle beam scans for reflectors transverse and parallel to the welds. Straight beam scans were made for attenuation, angle beam interference and wall thickness measurements to assist in plotting I.D. surface geometry and to define the extent of examination coverage. Examination results for both Byron and Braidwood are summarized in Attachment 3 of the enclosed report.

All indications identified during the examinations were evaluated as acceptable to Section XI requirements. Limitations of examination coverage are identified. Outer diameter geometry of some welds precluded inspection of the Code required examination volume.

The ultrasonic examination performed on the cast stainless steel welds to Byron Unit 2 and Braidwood Unit 1 represent Commonwealth Edison's best effort ot meet Section XI preservice examination requirements. Relief from Code requirements is required since the ultrasonic procedure was proven to detect only major weld flaws. Also, the extent of examination coverage was limited on some welds. Relief requests for the Byron Unit 2 and Braidwood Unit 1 examinations are provided respectively in Attachments B and C to this letter. These relief requests will be incorporated into the preservice inspection program plans at the sites.

Please direct any questions you may have concerning this issue to this office.

One signed original and fifteen copies of this letter and enclosure are provided for your review.

Very truly yours, klM A. D. Miosi i Nuclear Licensing Administrator cc: L. Olshan J. Stevens 2061K l

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. ULTRASONIC EXAMINATION OF CAST STAINLESS COMPONENT WELDS AT BYRON UNIT 2 AND -

BRAIDWOOD UNIT 1 9

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ABSTRACT This report summarizes the results of pre-service ultrasonic inspections performed on the weldments joining statically cast austenitic stainless steel (SA-351 grade CF 8A) fittings to various components in the heavy wall reactor coolant piping at Byron Unit-2 and Braidwood Unit-1. The examination procedure / technique was developed and optimized by Commonwealth Edison and demonstrated to the satisfaction of the Nuclear Regulatory Commission (NRC) representatives on June 26, 1986 at Braidwood. Contractor personnel (Ebasco Services, Inc.) performed inspections at Byron Unit-2, and Commonwealth Edison personnel inspected Braidwood Unit-1. All NDE personnel were trained to perform these examinations to Commonwealth Edison's procedure NDT-C-38, Rev O, dated June, 1986. As recommended by the NRC, every weldment in both units has been examined to the extent possible, and any limitations due to the geometry and jolut configuration for complete coverage were noted and are reported in this summary report. All recorded indications have been evaluated as acceptable to the ASME Section XI.

1.0

Introduction:

An interim report submitted to the NRC (Letter from Mr. K. A.

Ainger to Mr. H. R. Denton dated June 25, 1986, NRC Docket Nos.

50-454/455 and 456/457) described progress made by Commonwealth Edison toward development of an ultrasonic examination (UT) procedure / technique for performing pre-service volumetric inspection (PSI) of various cast components in the Byron Unit-2 and Braidwood Unit-1 reactor coolant piping systems. This developmental program showed that an improved, state of the art UT technique will detect large flaws (25% or greater thru the wall), if present, in most of reactor coolant piping components. The procedure / technique was demonstrated to the satisfaction of the NRC representatives on June 26, 1986 at the Braidwood Construction site. The ability of this UT procedure to penetrate the cast material to the I.D. surface and its sensitivity to find defects was demonstrated utilizing a mock-up and a cracked specimen obtained from the Westinghouse PWR owners group.

2.0 Procedure / Technique:

Details of the developmental program culminating in a viable procedure / technique for inspection of static cast stainless steel components are presented in a separate report (Attachment 1). The Commonwealth Edison procedure. NDT-C-38 Rev 0, June, 1986 (Attachment 2), represents the best effort, state of the art procedure that attempts to meet ASME Section XI requirements for volumetric examination to the extent possible. Basically, it calls

for use of a 1-inch dia. x 1.0 MHZ focused dual element refracted L-wave transducers, Panametrics EPOCH 2002, or equivalent UT scope, and calibration standards made to the requirements of the ASME code. The contact transducers are mounted on axial and circumferential contoured wedges and produce a focused, refracted L-wave to an approximate 41 degree angle of incidence. The calibration standards employed are actual sections of a full size statically cast 31 inch to 29 inch reducing elbow, specially selected on the basis of similar ultrasonic attenuation to the Byron /Braidwood fittings.

The calibration procedure requires the use of side drilled holes for the sweep set up, and the use of 10% and 25% notches for the sensitivity standards. Scanning sensitivity is specified to the noise level of 10 to 30 percent of full screen height.

3.0 Training of UT personnel:

Ebasco Services, Inc. have the contract for PSI of Byron Units 1 & 2. Commonwealth Edison performed the baseline inspection on i Braidwood Unit-1. Personnel, from both organizations, performing the inspections were ASNT certified Level II inspectors. They received forty hours of additional training for procedure / technique i familiarization. A mock-up consisting of a full size statically cast stainless steel elbow welded to a wrought piece of pipe was used for the training purposes. Test samples made from a cast elbow welded to a wrought pipe and containing both thermal and mechanical fatigue cracks, which were obtained from Westinghouse PWR owners

group, were also used. The inspectors demonstrated their proficiency to the satisfaction of the Ceco Level III by their ability to detect notches in the mock-up and cracks in the owners group samples. The requirements in the procedure for recording and evaluation of signals, profiling of weld contours and identifying physical or metallurgical constraints for complete examination were explained to the inspectors in detail.

4.0 Inspection Results A total of fifty-six welds were examined from the cast side in each unit (Byron 2 and Braidwood 1).

The number of welds at various locations are as follows

1. Reactor safe end-to-cast elbow - 4

2. Steam Generator Nozzle-to-cast elbow - 8

3. Forged pipe-to-cast elbow - 20

4. Forge pipe-to-cast pump casing - 4

5. Forge pipe-to-cast valve body - 12

6. Cast elbow-to-cast pump casing - 8 Total welds 56 The summary results of the examinations are presented in . Detailed inspection reports are available at the respective plant sites. The angle beam refracted L-wave examination of these welds was supported with a straight beam examination for attenuation measurement, angle beam interference and wall thickness measurements, to assist in plotting I.D. geometry and to define the extent of coverage. Contour gauges were used when necessary to show

actual weld profiles at the O.D. Angle beam examinations were All performed to detect flaws parallel and transverse to the weld.

restrictions which precluded 100% coverage were noted.

Specific comments on each weld are given in the summary reports (Attachment 3). In general, the valve body contour on the O.D.

surface presented some limitations during the axial scan.

Circumferential scans (for longitudinal defects) were limited to a short distance from the edge of the weld crown for both the valve As and pump welds because of the physical shape of these castings.

a result, the extent of coverage required by the procedure could not be obtained. However, the primary interest in pre-service and in-service volumetric examination is to detect any flaws in a volume of metal adjacent to the weld, near the I.D. surface. This area could be defined as the volume of metal in the counterbore region t

including the weld metal. Both axial and circumferential scans were capable of locating any defects within this area of interest. This l

(

is verified by the fact that root and counterbore signals were identified even though the extent of coverage was reported to be limited in the inspection reports.

In addition to obtaining root and counterbore signals on most of the welds, base metal inclusion indications were noted in six Byron welds and five Braidwood Unit-1 welds. A review of construction radiographs confirmed the presence of base metal inclusions in some cases. Supplementary UT examinations were performed and construction drawings were reviewed to assist in the

evaluation of recordable indication, whenever necessary. All 1

recorded indications were evaluated as acceptable to ASME Section XI.

5.0

Conclusion:

Pre-service volumetric examinations to the extent possible have been completed on all statically cast stainless steel component

! welds using the latest, state of the art ultrasonic examination procedure / technique on both Byron Unit-2 and Braidwood Unit-1 l i reactor coolant piping systems. The UT technique was proven to be capable of detecting any major flaws present or possibly initiating in-service, in the areas of interest near the veld I.D. Weld root and counterbore signals obtained on the majority of the welds showed the ability of this technique to penetrate ultrasound into I statically cast stainless steel to the I.D. surface, i Reflectors identified in the 41 RL examinations were i evaluated / verified by 0 plotting, review of the applicable l radiographs when necessary, and supplemetary UT examinations. All

! recorded indications have been evaluated as acceptable to the ASME Section XI code acceptance criteria. However, relief from the requirements of IWB-3514 is required due to the nature of the examination sensitivity and the extent of coverage possible.

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0119P

A TTA CHMENT 1 Development of UT Inspection Technique / Procedure for Static Cast Stainless Steel Components in PWR Piping Systems

Devolep20nt of a Rollablo Ultraconic T00t Technique for Static cast stainless Steel Components in PWR Piping Systems i

1 i 1.

Introduction:

l 1 The nuclear industry and regulatory agencies approach to ensure the integrity of nuclear piping systems is strongly dependent upon i the reliable, in-service volumetric examination of the component

. welds. Of the two volumetric examination techniques, radiography l and ultrasonics, ultrasonic inspection technique is considered more J practical and reliable than radiography for in-service inspection (ISI). The ISI requirements are specified in 10 CFR 50.55a(g), 1 1

1 which in turn legally incorporates ASME Section XI, by reference.

I The ISI program requirements in Section XI require that pre-service inspection (PSI) be performed on various components and weldsents

)

I before the nuclear unit is placed into service.

! Commonwealth Edison Co.'s Byron and Braidwood, Units 1 and 2, are l Westinghouse four loop pressurized water reactors of essentially i

identical designs. Eacn plant utilizes statically cast stainlass i

steel fittings (elbows), pump casings and valve bodies in the reactor coolant systems. The material specificatione for the pump casings and valve bodies is SA351-CF8M and for the elbows SA351-CF8A. The piping is made of wrought stainless steel to SA376-304N (forged pipe) specification, j Unlike wrought stainless steel pipe welds, the code required ultrasonic inspection of cast stainless steel components has been recognized as extremely difficult to perform due to severe l 1

attenuation, scattering and angle shift of the sound beam.

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Pre-service examinations on Byron Unit-1 were performed using the best available technique at that time. Where possible, examinations were conducted from the wrought pipe side only and some credit was taken for the ultrasound penetration through the weld, to a limited extent, into the cast stainless side. Exemption from examination from the cast side was requested from the NRC. However, because substantial progress had been made in the industry since the Byron-Unit 1 PSI towards the development of a reliable UT technique for examining the cast components, the Nhc requested that Byron Unit-2 and Braidwood Unit-1 be examined on a "best effort" basis.

This best effort would involve surveying the techniques used at other plants, developing a procedure that would represent the latest state of the art, and performing ultrasonic examination to the extent possible on every weld from the cast component side. Only then, would the NRC consider a relief request, if needed, on a weld by weld basis.

i 2. Industry Survey:

I

, Commonwealth Edison contacted the Electric Power Research l

! Institute personnel who had participated in the Georgia Power's i

! Vogtle Unit 1 PCI. On November 18, 1985, Dr. Xavec Edelman and Mr.

J. Mark Davis of EPRI visited the Byron site to examine the Byron

! Unit-2 cast stainless steel components with the UT technique that was used at Vogtle. They concluded that due to the lack of a representative calibration standard they could not perform a meaningful examination of Byron components. They also stated that the statically cast Byron components were more attenuative than the

centrifuga11y cast components at Vogtle. They recommended that ,

l Commonwealth Edison's NDE personnel visited the Vogtle plant to become familiar with everything that was done at Vogtle and then undertake a developmental program to improve the procedure which would be needed to examine the statically cast components at Byron-2 and Braidwood-1.

The UT technique used at Vogtle basically involves the use of carefully designed 1.0 MHZ dual element nominal 45 degree angle beam refracted L-wave transducers, and use of appropriate calibration standards. On the other hand, Westinghouse, who performed the PSI for Yankee Atomic Electric Company at Seabrook Unit-1, used R-L fixture (booted shoes with water column) utilizing 41 angle beam refracted L-wave transducers. The Yankee Atomic report states that this Westinghouse technique was demonstrated to the NRC at several plants including Wolf Creek, Commanche Peak, Callaway and Millstone III.

3. Calibration Standard:

Statically cast stainless steel elbows were available at the cancelled Marble Hill plant. Commonwealth Edison personnel visited Marble Hill on January 7, 1986 and examined nine statically cast elbows, out of which one 31-inch to 29-inch reducing elbow was selected as having comparable attenuation to that of the Byron /Braidwood castings. The attached Table 1 shows the results of attenuation measurements made on the original calibration block used in the Byron Unit-1 inspection, representative values for Byron Unit-2 and Braidwood Unit-1 static cast elbows, the Vogtle

d calibration blocks, the Marble Hill 31 to 29-inch reducing elbow and representative values for the new calibration blocks prepared from this reducing elbow. ..

Four calibration blocks were machined from this elbow; two from i

the 29-inch diameter end (2.34 inch final machined thickness) which had lower overall attenuation and two from the 31-inch diameter end (2.83 inch final machined thickness) which had higher attenuation.

Both axial and circumferential side drilled holes (S.D.H.) and I.D.

notches were machined into each block. The S.D.H.'s are 3/16 inch .

diameter and are located at 1/4, 1/2 and 3/4 T locations. The I.D.

notches were machined to 10, 25 and 50% throughwall depths.

4. Search Units:

One set of calibration standards was sent to Krautkramer Branson l (KBA) and the second set was shipped to Harisonics Labs. Each set 1 concieted of one 2.34 inch thick calthration block and one 2.83 inch thick calibration block. The transducer manufacturers were

! requested to build angle beam refracted L-wave transducers producing f optimum results on the 10% and 25% deep I.D. notches. KBA made a l

set of search units sooner than Harisonics and delivered to Ceco for evaluation. A set consisted of one unit for the axial scan and one for the circumferential scan.

Each search unit consists of two, 1.0 inch dia. x 1.0 MHZ, Alpha series flat-facod transducers mounted on contoured, removable wedges

! that produce an approximate 40 to 45 degree, dual, refracted 1 longitudinal wave focuaned near the calibration block !.D. surface.

The actual focal point appeared to be somewhat beyond the I.D.

surface.

5. UT Results on Calibration Blocks:

Using KBA supplied search units, tests were conducted on both calibration blocks using the Nortec 131, Sonic Mark 1, Krautkramer USIP 11 and Panametrics EPOCH 2022 UT machines. The EPOCH 2002 g

produced the best signal-to-noise ratios (at 0.5 MHZ filter on the 10% and 25% I.D. notches). The USIP II and Mark I were adequate, but not as good as EPOCH 2002. The Nortec 131 was found inadequate for angle beam examination.

One interesting observation was that despite attenuation difference between the two calibraion blocks, approximately the same results were obtained with respect to the background noise (10 to 20% screen height at the reference sensitivity) and the signal-to-noise ratio (2 or better) for the I.D. notches.

Since the ec=bination of KBA anarch untra and the EPOCH 2002 UT machine produced good results, no further evaluation of the Harlsonics transducers was performed.

6. UT Technique /i'socedure Verification:

For the purpose of verifying the ultrasonic technique would work on actual components, it was decided to obtain a full size mock-up.

Conversation with Marble Hill personnel revealed that they had a spool piece in storage made of a 27.5 inch 1.D., 25 degree statically cast elbow welded to a wrought piece of pipe using the GAW process. Commonwealth Edison purchased the spool piece and had

f it sectioned lengthwise to provide access to the I.D. surface.

Notches were ground into the I.D. surface on the elbow side at various locations and varying depths using a very thin cut-off wheel. Both circumferential and axial notches were cut. Notch depths were 10%,

25% and 50% thru wall. Circumferential notches were located very close to the I.D. weld root and midway between the weld root and and l 1

of the counterbore. An axial notch was cut across the weld root at the I.D.

In addition to this mock-up, four pre-cracked samples were obtained from the Westinghouse PWR Owners Group. These samples were made from segments of statically cast elbows welded to wrought pipe I

pieces. Two samples contained mechanically induced fatigue cracks and the other two contained thermal fatigue cracks. The crack l depths were 1.0" and 0.5" for the mechanical fatique cracks, and 0.7" and 0.85" for the thermal fatique cracks. The elbow side of l

these semp1== were in the ad-cast condition, unlike the actual elbows at Byron and Braidwood where the O.D. surface has been machined to a distance of about 6-inches from the weld centerline.

1 Notches in the mock-up and cracks in three of the four owner's Group samples were detectable using the newly developed UT l

procedure / technique. In one Owners Group sample, the crack could not be detected because of the O.D. geometry. Transducer " lift-off" i

occurred resulting in a loss of contact near the weld crown and

( making crack detection difficult in this sample. However, this crack and cracks in the other three samples were detectable from the i

pipe side using the same refracted L-wave technique.

Detection of notches in the mock-up and cracks in the owner's Group samples were easily verified by using a " dampening" technique. Furthermore, the counterbore and the I.D. root bead signals were also detected and verified using the dampening technique. The ability of the refracted L-wave to penetrate a statically cast structure was proven. However, an interesting observation made during these tests, which cannot be easily explained was the sweep location of the signals from the notch and the cracks did not coincide with the expected location for such signals.

Figures 1 through 4 illustrate the phenomenon observed. Figure 1 shows the UT signals from the owners group sample when scanning back away from the weld on the cast side. The signal from the crack should have appeared ahead of the counterbore signal. Instead, it always stayed further out on the sweep distance. Similar observation was made on the 25% notch signal from the mock-up as shown in Figute 3. The reason for the notch or crack cignal to appear at approximately "5/8 node" rather than "3/8 node" is not known. Mode conversion and/or angle shift are possible causes for this anomoly.

Even though there is no explanation for this observation, it must be accounted for in the UT procedure. Normally, a UT procedure for pipe weld examination would require recording and evaluation of indications with the 1/2 V path or distance of the sound travel, llowever, as a result of this observation where the signal from coal reflectors appeared past the 1/2 V path, the procedure was written requesting the inspectors to record all indications. They also were

trained on the mock-up to observe this phenomenon and account for it when performing actual pre-service inspections. They demonstrated their proficiency by detecting cracks and locating them in the Owners Grou? samples.

7. Metallurgical Examinations:

Problems associated with ultrasonic examination of cast austenitic stainless steel are attributed to the as-cast microstructure. Sample pieces were removed from the 31.0 to 29.0 reducing elbow which was used to prepare the calibration blocks.

Mill certification and the heat treat charto for this elbow (attached) show the SA351-CF8A steel was solution annealed at 2000 F for 4 houro.

The attenuation measurements showned the thinner block to exhibit (29.0 inch end) 1000 attenuation than the thick block (31.0 inch end). Meta 11ogtaphic specimens were prepared from samples removed from both undo for microstructure examittation. Figura % nhown representative microstructures near the O.D. surface (Fig. Sa), at midwall (Fig. Sb) and near the I.D. surface (Fig. Sc) of the thin block. The microstructure of the thick block to similarly shown in Figures 6. A wold repair performed, probably during manufacture, in the thick block cample (Figure 6c). A was found near the I.D.

i variation in microstructure from completely dendritic to a mixture of equiaxed and dendritic to a comewhat fully equiaxed structura in observed in the same specimen. Moreover, the same elbow, which wan cast in one piece and heat treated as one piece, showed a 1/2" thick

_9 wide variation in microstructure from one end to the other. A test sample was re-heat treated at 2050 F for 1 hout and examined to determine the adequacy of the manufacturer's heat treatment. Figure 7 shows the microstructure of the lab solution annealed piece. The microstructure appeared to be somewhat modified; the grain structure is more equiaxed and less dentritic. However, the difference in the structures of the as-received and lab anneated specimens are not sufficient to make any positive conclusions with respect to the mill solution anneal.

The wide variation in attenuation measurements reported during actual inspections of Byron and Braidwood components and calibration blocks from different sources is a result of variations in the cast material microstructure. This has long been recognized in the industry, and was confirmed by this study.

8.

Conclusion:

The program undertaken by Commonwedith Edison has resulted in development of a viable ultrasonic inspection technique which will i

detect large flaws in statically cast austenite stainless steel i components. The technique / procedure was demonstrated on full size mock-ups and actual cracked samples. The wide variation in 1

attenuation of ultrasound energy by cast components is attributed to microstructural variations within a cast component, which was

! confirmed in this investigation. Further work is needed to account for the observation made with regard to 1.D defect signals appearing i

at unanticipated position on the sweep scale.

0121p

TABLE NO. 1 ULTRASOMIC ATTENUATION MEASUREMENTS OF CAST AUSTEN1 TIC STAINLESS STEEL CALIBRATION BLOCKS AND COMPONENTS Plant Straight Beam 450 Thru/Trans.

and/or httenuation Attenuation Comments Component (s) dB dB dB dB Lcw High Low High Byron Cast Safe-end Block is flat and has surface Calibration Block 40 59 63 63 and size restrictions for 450 thru.

Byron Unit #2 Could only resolve 1st back Cast Elbows 48 64 66 68 reflection on elbows examined.

Braidwood Unit #1 Resolution varied from 3rd back Cast Elbows 41 68 50 71 reflection to poor 1st back reflection.

Vogtle Cast The 2nd back reflection Calibration Blocks 38 55 53 60 was resolved most of the time.

Marble Hill Cal-blocks listed below were Reducing Elbow 35 59 49 65 cut from this elbow.

29* Dia./2.34*T Not Not Taken Refer to Attachment #1 Calibration Block 40 51 Taken 31" Dia./2.83*T Not Not Taken Refer to Attachment #2 Calibration Block 45 58 Taken Note: All attenuation measurements were taken with the Panametrics, EPOCH 2002, UT-Machine.

All straight beam attenuation measurements were taken with KRA I.0" dia.x 1.0 MHZ Trans.

All 450 Thru Transmission measurements were taken with 2-Harris 1.0" sq x 1.0 NHZ Trans.

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