ML20106E438

Nonproprietary Westinghouse Modified D2 & D3 Steam Generators Performance Summary Rept

ML20106E438
Person / Time
Site:	05000000, McGuire
Issue date:	07/05/1984
From:	WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML082321458	List: ML20106E438
References
SG84-07-008, SG84-7-8, NUDOCS 8410290232
Download: ML20106E438 (91)

Text

- - _ _ _ _ _. _.

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,a SG84-07-008 MODIFIED D2 AND D3 STEAM GENERATORS PERFORMANCE SLMMARY REPORT 1

JLILY 5, 1984 2

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8410290232 840928 PDR ADOCK 05000369 p

PDR 1307c/0188c/071184:5 1

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-o TABLE OF CONTENTS I.

INTRODUCTION AND

SUMMARY

A.

Introduction B.

Sumary C.

Conclusions II. D2 AND D3 MODIFICATION DESCRIPTION A.

D2 and D3 Design Description B.

Modification Description III. PLANT INSTRUMENTATION AND DATA REDUCTION A.

Pre-Modification Data 8.

Pre-and Post-Modification Data Comparison C.

Pre-/ Post-Modification Plant Data / SSP 8 Full Scale Teet Data Comparison D.

Sunmary/ Conclusions IV. ED0Y CURRENT EXAMINATION AND EVALUATION A.

Typical Pre-Modification Data B.

Post Modification Data C.

Conclusions V.

ALMARAZ PREHEATER INLET MODIFICATION VISUAL INSPECTION A.

Technical Discussion B.

Conclusions 1307c/0188c/071184:5 2 2

J I.

INTRODUCTION AND SLM1ARY In October of 1981, a tube leak occurred in one of the steam generators ir$ the Ringhals 3 pow?r plant in Sweden. The Ringhals 3 power plant contains three (3) Model D3 steam generators, which are of the splitflow preheater design.

The plant was shut down and an investigation as to the cause of the leak was started. Eddy current examination (ECT) of the steam generator tubes in each of the stean generators at the Ringhals 3 plant revealed indications of wall i

i reduction. The indications were located primarily in the first three rows of tubes adjacent to the feedwater inlet. At the time of the shutdown the Ringhals 3 power plant had operated for a total of 113 effective full power days.

The Almaraz 1 power plant in Spain was also in operation with Model D3 steam l

generators.

It was shut down for steam generator inspection in October of 1981. The results obtained from the Almaraz 1 steam generator ECT examination i

were similar to those obtained from Ringhals 3.

In addition to performing eddy current examination of the tubes in the steam generators, tubes were removed from Ringhals 3 and Almaraz 1 for laboratory examination. The types of examinations included profilometry, macroscopic

(

visual, microscopic, scanning electron microscopic, radiography and hardness.

These examinations confirmed that wear was the cause of the tube wall reduction.

There are two models of Westinghouse splitflow preheat steam generators,

(

Models D2 and D3. The primary difference between the models is that the Model D3 steam generator contains a flow distribution baffle between the tubesheet i

and the first tube support plate whereas the Model D2 does not.

l At the time of the Ringhals 3 tube leak, there were 3 plants in operation using steam generators of the Model D2 or D3 design. The plants were:

l l

1307c/0188c/071184:5 3 i

[

i Plant Location Steam Generator Model Ringhals 3 Sweden D-3 Almaraz 1 Spain D-3 McGuire 1 USA D-2 Due to the findings at Ringhals 3 and Almaraz 1, W recomended that the three plants operate at a reduced power level, pending development and installation of a modification to address the tube wall reduction issue.

In response to the findings at Ringhals 3. Westinghouse undertook a program to investigate the cause of the tube wear phenomenon and to develop a modification to address it.

Efforts undertaken to identify the nachanism causing the wear included investigation of the. flow behavior within the preheat region using several scale model test facilities, a flow induced vibration dynamic analysis tube model, and a mechanical tube test model. The investigations resulted in the identification of turbulence in the preheater inlet plenum as the major excitation mechanism causing tube movement and subsequent wear. Evidence of fluid elastic excitation was discovered for tubes in regions adjacent to the impingement plate.

Primary functional requirements for the undification were, therefore, (a) to modify the character of the inlet plantsn turbulence and reduce its magnitude and (b) to promote more uniform flow into the tube bundle over a wide area and thereby minimize flow velocities adjacent to the tubes.

A modification to the preheater inlet region of the steam generators was designed which reduced the turbulence of the feedwater introduced into the tube bundle and distributed the feedwater over a larger area of the tube bundle than in the original design.

Section II of this report describes the D2/03 Steam Generator and the manifold modification.

l 1307c/0188c/071184:5 4

..D.

Pre and Post Modification accelerometer instrumentation results are described in Section III. This section compares both plant and full scale test data obtained before and after the modification.Section IV sumarizes the eddy current wear measurenent results obtained prior to the modification and the change in wear depths between pre-modification and post-modification data for up to six months of post-modification operation.

i i

1307c/0188c/071184:S 5

B.

Sumary The cause of the excessive tube wear in the Model D2 and D3 steam generators was identified as being due to exceptionally high flow velocity and turbulence in the inlet feedwater flow region. A modification to the inlet region was implemented consisting of the replacement of the installed impingement plate and four hole reverse flow limiter with a double perforated plate manifold and a nineteen hole fim limiter. The modification was designed to alter the character of the inlet plenum turbulence and reduce its magnitude to an acceptable level. The modification was designed to also promote uniform flow into the tube bundle over a wide area thereby minimizing flow velocities adjacent to the tubes. The manifold modification has been incorporated in all Model D2 and D3 steam generators.

Four Model D2/D3 steam generators were instrumented with accelerometers in selected tubes prior to the manifold modification and five, including the initial four units, were instrumented after the manifold installation. A sixth unit has been instrumented with the manifold installed but data from this imit were not available at the time of the report. An objective for the manifold modification was to obtain tube vibration levels at 100 percent power comparable to the pre-modification measurements at 50 percent power. At 50 percent power operation prior to the modification, negligible wear was indicated by eddy current measurements. The post modification accelerometer data shm that vibration levels, as indicated by the displacement data and the Ga product of acceleration and displacement, are generally less than the pre-modification values at 50 percent power. The post modification data are also consistent with the full scale model test data obtained as part of the manifold modification design effort.

Post-codification eddy current measurements have been obtained and evaluated for four plants. These data were obtained for up to six effective full power months of operation after the manifold installation. The eddy current results shm that no new tube wear indications have been found at the preheater support plates locations. For tube wear indications found prior to the manifold modification, the average depth ch'enge per generator was found to vary from approximately -1 percent to +4 percent. These changes are well 1307c/0188c/071184:5 6

within the typical scatterband of +10 percent for eddy current measurements and are not indicative of further wear.

A fiberoptic system, entering the modificaton by means of an access port in the feedwater piping, has been used to examine circumferential welds of the modification components to the feedwater nozzle thermal liner and linear welds at the flow splitter vanes.' This inspection shows that fiberoptics is a viable means for visual examination with sufficient resolution to detect significant structural changes, surface indications and foreign objects such as in the entrance plate holes.

Small foreign objects can be retrieved from the reverse flow limiter and entrance plate region of the modification.

1307c/0188c/071184:5 7

C.

CONCLUSIONS The available post-modification plant accelerometer data and eddy current measurements indicate that the manifold modification objectives for reducing tube vibration levels have been achieved.

Specifically, 1.

Measured post-modification vibration levels are less than or comparable to the design objective levels obtained at 50 percent power prior to the podi fica tion.

2.

Post-modification eddy current data for up to six months of operation have not detected any tubes with new wear indications and changes from prior wear indications are small and well within the scatterband of eddy current measurements.

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l 1307c/0188c/071184:5 8

O o

II. 02 AND D3 MODIFICATION DESCRIPTION A.

D2 and D3 Design Description The Model D2 and Model D3 steam generators designs are basically similar.

Figures 11-1 II-2 and II-3 illustrate certain aspects of the preheater sections of the two models,* showing some of the differences in design. The major difference between the Model 02 and Model D3 design is that the Model D3 has a flow distribution baffle (FDB) between the tubesheet and the first tube support plate, whereas the Model D2 does not (see Figures 11-1 and II-2).

Also, in the Model D3 steam generator design the center partition plate extends to the top of the preheater section, whereas in the Model D2 design, the partition plate extends only to the upper most preheater tube support plate or baffle plate, see Figure !!-2.

In addition, there is a difference in the impingement plate between the two nodels as shown in Figure II-3.

In both designs, the feedwater is introduced into the preheater area through the main feedwater nozzle. Before entering the preheater, the feedwater passes through a reverse f1w limiter which is an orifice device mounted within the main feedwater nozzic to provide a restriction to backflow in the event of a costulated feedline break accident. The original reverse flow limiter configuration was that of a large cylinder with four venturi nozzle penetrations. The limiter was welded to a support cylinder which was in turn welded to the nozzle thermal sleeve. Flow out of the four venturi nozzles was directed at an impingement plate assembly which was mounted upstream of the tubes and supported from metal bars extending between support plates 5 and 6.

See Figures II-1 and II-2. The impingement plate shielded the tubes from the direct force of the incoming feedwater. Some of the incoming flow did pass throegh the impingement plate assembly through staggered penetrations in the double perforated plates which sade up the assembly. Most of the incoming flow was deflected above, beim or to the sides of the assently.

1307c/0188e/071184 :S 9

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s 4 Within the preheater section, the feedwater flows into the tube bundle in the direction of the divider plate in the center of the steam generator. Vertical flow of the water is restricted by tube support plates through which the steam generator tubes extend. The flow enters the preheater between support plates 5 and 6 which form the inlet pass chamber.

As the flow reaches the divider plate, it is split into vertical upflow and downflow with the nejor portion of flow passing through cutouts in the support plates.

Both above and below the initial inlet pass, additional support plates form a series of chambers through which the flow is directed across the tubes. These crossflow chambers comprise the preheater section.

During normal operation, the feedwater is heated in the preheater region and exits from the top and bottom of the preheater as shown by the direction arrows of Figure II-1.

The flow from the preheater joins with the water and steam mixture in the remainder of the steam generator.

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I 1307c/0188c/071184:5 10

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B.

Modification Description The modification to the inlet plenum of the Model D2 and D3 Steam Generators significantly reduces tube vibrations by reducing the level of turbulence in the feedwater flow entering the tube bundle. The modification consists of the addition of an internal manifold and replacement of the four hole reverse flow limiter with a 19 hole reverse flow limiter. The manifold is designed, also, to distribute the flow to the tube bundle in a more uniform manner than was achieved by the originally installed impingement plate configuration. The 19 hole reverse flow limiter provides a more uniform flow to the inlet plenum than did the four hole reverse flow limiter.

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The discharge area of the manifold exit penetrations isj'ogt[,] times the I

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the area of the nozzle. This distribution of flow to the heat exchanger tube

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bundle is spread over percent of the width of the first row of tubes with the manifold installed.

The modification was made through the feedwater nozzle. The assembly is welded to the nozzle thermal liner with no supports internal to the steam 9enerator plenum area required. The individual features of the modification are shown on Figure II-4, an exploded view is shown on Figure II-5 and a section illustration is shown on Figure II-6.

At the entrance of the steam generator nozzle the four hole reverse flow limiter has been replaced by a 19 hole reverse flow limiter of equal net flow area (0.22 ft.2). The larger number of smaller holes in the 19 hole reverse flow limiter results in smaller flw jets, which provide a more fully developed flow entering the internal manifold. The 19 hole reverse flow limiter thus provides a quicker degradation of peak jet velocities which assists in the reduction of turbulence.

The internal manifold assembly, illustrated on Figures II-4 and II-5, consists of six box assemblies, a flow splitter, a support sleeve, and bolting for assembly of the six boxes.

1307c/0188c/071184:5 11

PREHEATER INLET MODIFICATION G

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Flow entering the manifold is divided into six flow channels by the flow splitter. Each channel feeds one of the six manifold boxes. Flow turbulence associatedwiththejetsfromtheflowlimiter,[

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The natural frequency of the manifold and its components is no less than twice the fluid excitation frequency. Erosion and corrosion considerations were addressed by the choice of materials, design co4 guration and hole sizes.

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The final design was analyzed considering nominal full power feedwater flow as well as the full range of normal and transient conditions including f aulted and test conditions.

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III. PLANT INSTRUMENTATION APO DATA REDUCTION Selected steam generator tubes at Ringhals 3, Almaraz 1, McGuire 1 and V. C.

Summer were internally instrumented with piezoelectric biaxial accelerometer strings. Accelerations were neasured in two orthogonal horizontal directions at each accelerometer location. To support the accelerometers within the tubes, spring fingers were attached to the accelerometers. Spring fingers were also placed along the instrumentation cables within the tubes to minimize extraneous signals due to cable motion. Figure III-1 presents a typical accelerometer configuration.

Installation of the accelerometers was accomplished by cutting the selteted tubes in the U-bend area between the top support plate and the first anti-vibration bar. The accelerometers were then inserted into the tube from the top and pulled into position from the bottom. After measuring the accelerometer locations and orientations, the tubes were plugged at the tubesheet. The top and of the tube was left open to the secondary side water. Conduit was installed between the cut end of the steam generator tube and the instrumentation penetration point on the steam generator upper shell to protect the instrumentation leads.

Prototypical internal accelerometers were tested at the Westinghouse Research and Development Center to evaluate typical as-mounted response characteristics. The amplitude response of the accelerometers is dependable for frequencies between 15 and 600 Hz.

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A schematic of the plant instrumentation and data acquisition system is shown in Figure III-2.

The output of a biaxial accelerometer was input into a pre-amplifier. The pre-amplifier was mounted in an instrumentation junction box located inside the containment building close to the stesn generator. The j

output of each pre-amplifier was passed through the containment penetration and then input into a charge amplifier.

Before being recorded, the signal from the charge amplifier was further conditioned usi ng a signal conditioning amplifier. All signals were recorded on magnetic tape for later analysis.

1307c/0188c/071184:5 13

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FIGURE III-2 SCHEMATIC 0F TYPICAL W STEAM GENERATOR TUBE VIBRATION MONITORING DATA ACQIIISITION SYSTEM SIGNAL PATH 1

1

The accelerometer locations for the various plants are shown on Figures III-3 and III-4. These figures show the locations of the accelerometers used during both the pre-and post-modification testing. The accelerometers are designated by the column number and elevation, e.g., accelerometers in tube R49C51 located between Tthe Support Plates (TSP) 5 and 6, are designated 51-5.5 and accelerometers located in tube R49C51 at the elevation of TSP 7 are designated 51-70.

Data recorded at the plant site were reduced by Westinghouse. The objective of the reduction was to provide information that would determine the vibrational amplitudes, the frequency content and the relationships between various accelerometer signals.

Spectral analyses were performed using a Westinghouse Digital Data Analysis Package or a Nicolet 660B, dual channel analyzer.

Figures III-5 and III-6 define the notation on the frequency spectral and time history plots.

[Jb Theproductofthe{

g has been correlated with the level of tube wear that has occurred in Model D steam generator preheaters. The amount of wear is related to the amount of wort expended during the wear process. An indication of the work done by the tube on the baffles can be inferred from the vibration measurements. {

[hi vibration wear parameter, Ga, provides a means for characterizing wear at different power levels and in different plants and is presented to aid in the evaluation of test results.

1307c/0188c/071184:5 14

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A.

PRE-MODIFICATION DATA Pre-modification data were collected at 4 plants, Almaraz Unit 1, Ringhals Unit 3, McGuire Unit 1, and V. C. Summer.

Steady state data were recorded at various power levels including zero power. The maximum power levels which were recorded during pre-and post-modification testing are summarized in Table III-A.1.

A sample of the pre-modification 0-200 Hz RMS acceleration spectra are shown inFiguresIII-A.1andIII-A.2.(

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1 6., c, t-4 Tables III-A.2 and III-A.3 contain the 15 - 100 Hz RMS displacements and the calculated Ga values for 50 and 100 percent powers. (

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1 FIGURE III-A.1 TUBE R49C51 - 6.5K ALMARAZ UNIT 1 l

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POST KD.

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TUBE POWER TUBE POWER PLM f0.

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RINELS 3 W45 100%

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W51 100,80/20 W58 100%

W58 100,80/20 49/68 100%

W68 100,80/20 RItGRLS4 W40 100%

90/10,80/20 W60 100%

90/10, 80/20 1

M 100%

90/10,80/20 l

V. C. SLMR W51 50%

49/51 100%

W57 50%

W 57 100%

l FCGUIRE1 WW 75%

49/31 100%

W%

10 I

49/50 10 l

M 75%

W71 100%

l l

ALMAZ1 W51 100%

49/51 100%

M 100%

M 200%

1307c/0188c/071084:5 16

,ry,-wgi.--__

_,m.-.__.

_._y_____-._.,.,___.,,.o,,,-~%.,,

. m

- -. - _ _ _ _. - -,.,.._,___,_--,-,,__,.,.-_,_-__,_,--...-_.-.mme

A um

.s n

m-&4h-a V

a a

4 A-RAL 4

a a-J a

+a-.k k-.

6

- S TABLE III-A.2 E-/ POST-MODIFICATION Ga COMPARISONS 1

.r e

h 4

0 o

4 1

a F

l i

4 1

1.

L i

f,

l a

e i

4 l

i t

d i

l Em I

f i-L

(-

,.,,,,,,,.. -, - - -... -,,,,.,,,_...~.,,,.,,,,,., -,. _,.,,,,,,,, _ _,,, _,,,, - _ _ __.,,, --,-,,.,,, _, ---,.,

,-a-w,,,.-,,,,,n_,-

t'-.

{

TABLE III-A.3 M,4 C PRE-/ POST-MODIFICATION a RMS C(MPAR150NS 1

s Y

i i

i n

h a

D

a.d4C FIGURE III-B.2 Tube R49/C515.5Y Pres and Post-Modification Acceleration Spectra Comparisons

r a

45,4 <-

i i

)

4 J

l I

4 f

I l

l I

FIGURE III-8.3 Tube R49/C715.5K Pro. and Post-Modification Acceleration Spectra comparisons

Ab,4 <-

I E

d FisuRE III.

-Tube R49/C715.5Y Pre-and Post-Modification B.4 Acceleration Spectra Comparisons l

N

'" "- ~ '- - - -

,w.__

B.

PRE-AND POST-MODIFICATION DATA COMPARISON Post-modification data were collected at 5 plants, V. C. Summer, McGuire Unit 1, Ringhals Unit 3, Ringhals Unit 4, and Almaraz Unit 1.

Steady state data were recorded at various power levels including zero and full power. Also, at Ringhals Units 3 and 4, data were recorded at full power with split feedwater flow through the main and auxiliary feedwater nozzles (see Table III-A.1).

Figures III-B.1 and III-B.2 show a comparison' of the pre-and post-modification 0 - 200 Hz RMS acceleration spectra. (

e c., c., e Figure III-B.5 through III-B.8 show a comparison of pre-to post-modification acceleration time history plots.[

.., e

-. L L

l l

1307c/0188c/071184:S 19

.s.

c4d4 c i

l i

FIGURE III-B.1-Tube R49/C515.5X Pres and Post-Modification I

Acceleration Spectra Comparisons i

/

h l

FIGURE III-B.2 Tube R49/C515.5Y Pres and Post-Modiff catton Acceleration Spectra Comparisons

4 i

i i

l t

FIGURE III-B.$ Tube R49/C715.5X Pre and Post-Modification Acceleration Spectra Comparisons i

I

\\

o 1

)

i FIGURE III. -Tube R49/C715.5Y Pre-and Post-Modtfication B.4 Acceleration Spectra Comparisons

c46,4 c.

i FIGURE III-B.6 Tube R49/C40 3.0f Pre-and Post-Modtffcatfon

Time History Acceleration Comparisons

45,4 <-

J FIGURE III-B.7 Tube R49/C715.5X Pre. and Post hdification Time History Acceleration Comparisons

/

FIGURE III-B.8 Tube R49/C715.5Y Pre-and Post-Modtfication Time History Acceleration Comparisons u_ :

Table III-A.2 and III-A.3 contain pre-and post-modification 15 - 100 Hz RMS displacements, and the calculated Ga values for all five post-modification plants. {

l SC t-L C.

PRE-/ POST-MODIFICATION PLANT DATA /SSPB FULL SCALE TEST DATA COMPARISON The Swedish State Power Board (SSPB) in cooperation with Westinghouse, erected and operated a full scale Model D3 preheater tube vibration test facility at the SSPB Alvkarleby hydraulics laboratory. THe SSPB full scale model duplicates the inlet pass of the nodel D3 preheater and includes a section of full length tubes representing the full height of tubes from the tubesheet to the U-bend elevation. Upper and lower pass flow conditions are not simulated and therefore this model is restricted to single pass effects. Provisions for adjustment of the tube support plates was provided to simulate the actual hot operating steam generator support plate conditions.

Support conditions were adjusted to achieve replication of operating tube vibration response based on comparison with the field measurements of actual tube vibration response.

Figures III-C.1 and III-C.2 show plots of RMS displacement and Ga values vs percent power obtained from the pre-modification SSPB test data and plant data. A comparison of these figures show that the plant data compare well with the SSPB full scale test data.

Figures III-C.3 and III-C.4 show similar plots of the post-modification SSPB full scale test data and plant data, respectively. A comparison of these figures shm that the post-modification plant data compare well with the SSPB full scale test data. Hence, the pre-and post-modification plant tube vibration data are consistent with the data obtained from the SSPB full scale model.

l e

1307c/0188c/071184:5 20

4 1

Up S

d 4

1 l

l 1

4 i

a 1

k I

i r

i h

j l-f f

i

[

..... m.c.,

I It

c

&i4 C-Figure III-C.2 D2/D3 Fre-Modification Plant Data

43,4 c.

i i

f Figure III-C.3 SfFB Fost-Modification Test Data

-.. -... ~. -- - - - - - - ' ~ ~ ~ ~ - ~

- ~ ~ ' ' ~ ~ ~ ' ~ ~ ' ^ ~ ~ ~ ~ ~ ~ ' ~ ~ ~ ~ ~ ~ ' ' ~

4S,4 C

't.

I 1

4 1i I

i i

i I

{-

i i

l 5

t I

e i

h i

Figure IIT-C.4 D2/D3 Post-Modification Plant Data 2

D.

SUP94ARY/ CONCLUSIONS Tube vibration data were collected at 5 plants equipped with nodel D2/D3 steam generators. Data were collected before and after the installation of a preheater inlet manifold modification, and were recorded at power levels ranging from 0 to 100 percent power.

Reduction and analysis of the recorded data provide a data base for the data summary shown in Table III-D.1, and the following observations and conclusions.

1.

The post-modification values of RMS displacement, peak-to-peak g's and.

Ga's at 100 percent power are generally less than the corresponding pre-modification values at 50 percent power. Operating experience with the unmodified configuration indicated low wear rates at 50 percent power.

It is thus expected that the design nodifications will result in a significant reduction in the wear rate. This has been confirmed by eddy current testing.

2.

Although tube support plate hole alignment can vary from generator to generator, the post-modification plant data show a tendency for improved tube support in addition to reduced vibration levels.[

o. m. c i

3.

Pre-and post-modification plant tube vibration data are consistent with data obtained from full scale test models.

1307c/0188c/071184:5 21

TABLE III-D.1 D2/03 POST MODIFICATION DATA SLpWARY Pre-Modification Data o 100 Percent Pqwer

• 6 a t

- Plant Data:

- SSPB Data:

~

o 50 Percent Power "f it-

- Plant Data:

Manifold Data

_e.L Sc o SSPB 100 Percent Power o Plant Data 100 Percent Power (5 plants)

a.,t., L Conclusions o Plant data at 100 Percent Power i SSPB Manifold at 100 Percent Power 1 re-Modification Plant Data at 50 Percent Power P

o Instrumented tube data indicates modification objectives are met 4

1307c/0188c/071184:5 22

i a

I V.

EDDY CURRENT EXAMINATION APO EVALUATION

' A.

Typical Pre-Modification Data Eddy current testing is typically used to inspect the heat transfer tube i

conditions in steam generators.

Initial eddy current testing at Ringhals 3, following the tube leak indicated degradation of the tubes of Row 49, 48 and 47 on the outlet (cold leg) side of the staan generators in the preheater region. Similar results were reported at Almaraz 1.

These initial inspections were made using the differential eddy current technique.

Continued development of eddy current testing methods resulted in the l

technique used presently which is a combination of a differential and absolute I

eddy current testing method. The absolute eddy current component is used to determine the depth of indications suspected to be caused by wear, the differential eddy current assists in locating the indications and also provides an inspection of the remaining tubing for potential degradation resulting from other mechanisms.

A combined differential / absolute eddy current inspection was conducted at Ringhals 3 in March 1982.

During this inspection,1668 tubes were inspected i

and 799 indications were identified.

Following the inspection, the plant returned to operation limited to a 40 percent power level and operated for 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />.

In June of 1982, an eddy current inspection similar to the one performed in March was conducted. A total of 1716 tubes were inspected and 610 indications were identified. The following table presents a summary of the inspection results.

i i

I l

t i

f 1307c/0188c/071184 :S 23

Ringhals-3 ECT Inspection Summary Inspection Item S/G 1 5/G 2 S/G 3 March 1982 Total Tubes Inspected 556 556 556 Tubes w/indicctions 80 439 280 June 1982 Total Tubes Inspected 572 572 572 Tubes w/ indications 52 338 220 The totals of the June inspection for indications were lower than that reported in March as a result of a change in the eddy current technique used and~ not due to a significant change in the stean generator tubing condition.

Eddy current testing is least sensitive in detecting and estimating depth for small indications.

Sensitivity and accuracy increase as the size of the indication increases. Many of the March indications were very small and were not again detected in the June inspection due to the limited sensitivity of eddy current testing for the small indications.

To provide additional information on changes in tube conditions between the two inspections, eddy current signals from the Ringhals-3 March and June inspection were reviewed using a signal to signal comparison method. The selection included a sample of all size indications including zero degradation.

If indications had grown in depth, a noticeable change in the i

eddy current signal shapes would have taken place.

If signal shapes are similar, no measurable increase in wear has occurred.

It was concluded that no measurable growth had occur; ed.

The initial inspection at Almaraz 1 in November 1981, found wear as in Ringhals 3 but not as advanced in terms of number of tubes and depth.

Following this inspection, operation was limited to 50 percent power for 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />. The next eddy current inspection was performed in March of 1982, followed by operation for 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> at 50 percent power and a third inspection in July 1982.

t The following table is a comparison between the March and July inspection results for indications of wall loss greater than or equal to_10 percent.

i 1307c/0188c/071184:S 24

i ALMARAZ UNIT 1 R0W 47-49 COLD LEG MARCH 1982 - ELY 1982 ECT COMPARISON OF INDICATIONS > 10 PERCENT ABSOLUTE S/G Row Column Plate March 1982 July 1982 Reading Number Number Nunter Abs Depth Percent Abs Depth Percent Change 1

49 54/6

<10 10 48 50/6 17 17 0

53/6 18 15

-3 54/6 20 17

-3 60/6 12

<10 2

49 68/7

<10

<10 3

49 47/6 11

<10 50/6 13 11

-2 57/6 21 23

+2 61/6 15 15 0

63/6 14 13

-1 55/6 12 11

-1 65/6 23 25

+2 68/6 15 15 0

• Cannot compute a reading change l

1307c/0188c/071184:5 25

This comparison shows that little or no change was observed in the condition of the tubes between inspections. The reading changes in the table of Almaraz inspectici results are within the accuracy range of normal eddy current testing, which is on the order of 10 percent.

In order to better compare tube conditions from March to July a signal to signal comparison was also made for the Alneraz 1 plant. This was accomplished in a manner similar to that for the Ringhals 3 plant. The thirty-fi'te signals reviewed using this method indicated no change in the condition of the tubes.

The McGuire-1 Plant has Model D2 steam generators. The first in-service inspection of the steam generators was performed in March of 1982 by a Duke Power subcontractor.

Differential eddy current was performed and revealed, five indications in Steam Generator C.

Following the March 1982 inspection McGuire-1 returned to operation, which was limited to 50 percent power with short periods of operation at 75 percent power. The next eddy current inspection was performed in June of 1982. A total of 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> were accumulated at 75 percent power. The inspection method employed was predominantly the differential method. A limited number of tubes were inspected using the absolute method. The results of the inspection are given in the following table.

McGuire 1 ECT Data TUBES WITH INDICATIONS IN BOTH MARCH AND JUNE l

Eddy Current Indication (Differential Method) (Percent) l l

S/G C Baffle No.

March June R49 C40 6

<20 27 1

R49 C41 6

< 20 34 R49 C74 6

<20

<20 R49 C75 6

< 20 20 R49 C76 6

<20

<<20 i

i 1307c/0188c/071184:5 26

The June inspection revealed 68 indications, occurring in all four steam 9enerators. Only 27 of the indications were due to wear. The breakdown of indications is as follows:

9 - > 20 percent wear indication 18 - < 20 percent wear indication 31 -

distorted signal 10 - PV, dent, or pilgering (Note 1)

Therefore, 27 readable wear indications were exhibited in June compared to five in March.

Note 1: PV (Permeability Variations), Dents (not occurring at a support plate), and pilgering are attributable to manufacturing.

l t

1307c/0188c/071184:5 27

B.

Post Modification Data The preheater inlet modification was completed at the Ringhals 3 plant in July 1983, in the W. B. McGuire No.1 plant in February,1983, at the V. C. Summer plant in May,1983 and at the Almaraz No.1 plant in June,1983.

Since that time, McGuire and Almaraz 1 operated approximately 6 effective full power months (EFPM) and V. C. Summer operated for approximately 3 EFPM before shutting down for eddy current inspection of the steam generator tubes. This section addresses the results of the first eddy current inspections following operation with the modification.

Description of Eddy Current Testing The eddy current techniques employed to inspect the tubes at all four plants were basically the same although three different testing subcontractor were employed by the utilities. At Almaraz 1. Technatom performed the inspection under Westinghouse supervision. At V. C. Sumer, the inspection was performed by Con-Am, Inc. and at McGuire 1 it was performed by Babcock and Wilcox.

Multiple-frequency eddy current techniques employing two differential and two absolute mode data channels were used in all three inspections. At Almaraz 1

]

and V. C. Sumer, the differential data channels were operated at test frequencies of 550 kHz and 130 kHz. The differential frequencies employed at McGuire 1 were 400 kHz and 130 kHz.

In all three inspections the absolute test frequencies were 300 kHz and 100 kHz. The wear scar depths are analyzed from the absolute mode data.

All data was initially analyzed on-site by the inspection subcontractor. This same data was re-analyzed by Westinghouse Steam Generator Technology Division and compared to that from prior inspections to nonitor the performance of the modification. The results are discussed below.

1 1307c/0188c/071184:5 28

.o Ringhal s-3 Westinghouse has not analyzed the ECT data from the last Ringhals 3 inspection. However, reports from the utility indicate that no further tube degradation has occurred since the modification.

V. C. Sumner This inspection was performed by Con-Am, Inc., who also did the on-site analysis.

No detectable wear at support plate elevations was reported.

Westinghouse re-analyzed the data from all tubes in Rows 44 through 49 in all three steam generators. The findings were consistent with those of Con-Am.

No wear was indicated at the support plate elevations in the preheater section of the stean generators.

W. B. McGuire No. 1 This inspection was performed and the initial data analyzed by B & W.

The results of a comparison of the 3/84 data to that obtained in 4/83 as analyzed by Westinghouse is shown in Table IV-I.

There was a slight negative change in the average wear depth in Steam Generator A, and a positive change in the remaining three steam generators. The results will be discussed in Section IV.C, Conclusions.

It is significent that no new indications were observed after 6 EFPM of operation.

Almaraz I This inspection was performed by Technatom and the data was analyzed by Zetec, Inc. The results of the comparison between 5/83 and 2/84 are shown in Table IV-II.

Steam Generator No. I shows a slight negative change in average wear depth and steam generators No. 2 and 3 show some small positive changes.

Again it is significant that no new indications were observed in the 2/84 inspection.

1307c/0188c/071184:5 29

TABLE IV-1 W. B. McGUIRE 1 STEAM NUMBER OF AVERAGE GENERATOR INDICATIONS CHANGE A

36

- 0.67 percent B

1

+ 4.00 percent C

3

+ 3.33 percent D

2

+ 3.50 percent Combined 42

- 0.07 percent 1307c/0188c/071184:5 30

.a' *,

TABLE IV-11 ALMARAZ STEAM NUMBER OF AVERAGE GENERATOR INDICATIONS CHANGE 1

10

- 0.20 percent 2

7

+ 1,71 percent 3

19

+ 4.32 percent Combined 36

+ 2.55 percent I

l 1

1307c/0188c/071184 :S 31 i

L

22-.

C.

CONCLUSIONS While Tables IV-1 and IV-11 indicate an average positive change (greater thru-wall penetration) in wear depth, it is Westinghouse's judgement that there has been no significant further tube degradation. The changes in indications, when viewed re]ative to the repeatability of ECT from one inspection to another, are not significant. At the 300 kHz test frequency, a scatterband of + 10 percent is considered typical. At the 100 kHz test frequency, the scatter is + 15 percent. The indication changes noted are well within these scatterbands. This coupled with the fact there were no new indications lead to the conclusion that the changes are not indicative of further wear.

1301dQ188dQ71184 :5 32

. _ ~. -

V.

ALMARAZ PREHEATER INLET MODIFICATION VISUAL INSPECTION A.

Technical Discussion The preheater inlet modification components of the three (3) steam generators of Almaraz Unit 2 were visually inspected in March 1983 prior to operation with the modification. This inspection was performed after the feedwater piping was rewelded to the feedwater nozzle and after subsequent hydrostatic pressure testing. An industrial fiberoptic system with 35mm attachments was utilized to perform the baseline inspection.

An existing access port in the feedwater piping used for inservice inspection of piping welds provided the access required for the visual examination. The fiberoptic probe was inserted through the existing port and manuevered through one of the Reverse Flow Limiter Venturi holes to gain access to the flow splitter and manifold.

By articulating the tip of the fiberscope, the desired position for observation and/or for taking photographs was obtained.

The examination concentrated on specific areas of the modification:

o Circumferential Welds (Figure V-1)

Reverse Flow limiter to the Support Cylinder Flow Splitter to Thermal Sleeve Manifold Support Sleeve to Thermal Sleeve Manifold to Manifold Support Sleeve o

LinearWelds(FigureV-2)

Flow Splitter Vanes to the Center Post Flow Sp1ftter Vanes to Ring 1307c/0188c/071184:5 33

4 4

m me FIGURE y.1 IftLDl#SftCTIONOFINMALLEDIEN1FE0

c.

A.C e b a

F19ere V-2 Weld Inspection of Installed Flow Splitter

..L.

s I

o Hardware Tapered Stud Assemblies High Strength Bolt Assemblies As-installed gap between the Flow Splitter and Manifold Entrance Plates o

Foreign Object Search At Almaraz 1, all three steam generatores had a visual inspection performed at the utilities initiative after operation. The inspection was made of the inlet modification components using the inspection pc,rt for access. The inspection was of sufficient clarity to provide assurance that Go surface abnormalities existed.

B.

Conclusions The visual inspection described above has provided a baseline with which to compare subsequent inspection results after an interval of operation. On the basis of the baseline inspection, the following conclusions can be drawn:

o Fiberoptic inspection of the preheat modification components is a viable means for visual observation; o

Photographic resolution is sufficient to detect significant structural changes or surf ace indications; o

Small foreign objects / debris can be successfully retrieved through the inspection port, o

Post operation inspections may be satisfactorily performed.

1307c/0188c/071184:5 34

I.

d.d 4 C l

l l

l l

l l

l FIGURE III-B.7 Tube R49/n7: 5.5X Pre-and Post-mdf fication f

Time H1 story Acceleration Conparisons

Oba G C FIGURE III-B.8 Tube R49/C715.5Y Pre-and Post-Modification Tfme History Acceleration Cooperf sons

l Table III-A.2 and III-A.3 contain pre-and post-modification 15 - 100 Hz RMS displacements, and the calculated GA values for all five post-modification plants.

9 m,c, t.

L C.

PRE-/ POST-MODIFICATION PLANT DATA /SSPB FULL SCALE TEST DATA COMPARISON The Swedish State Power Board (SSPB) in cooperation with Westinghouse, erected and operated a fu'll scale Model D3 preheater tube vibration test facility at the SSPB Alvkarleby hydraulics laboratory. THe SSPB full scale model duplicates the inlet pass of the model D3 preheater and includes a section of full length tubes representing the full height of tubes from the tubesheet to the U-bend elevation. Upper and lower pass flow conditions are not simulated and therefore this model is restricted to single pass effects. Provisions for adjustment of the tube support plates was provided to simulate the actual hot operating steam generator support plate conditions.

Support conditions were adjusted to achieve replication of operating tube vibration response based on comparison with the field measurements of actual tube vibration response.

Figures III-C.1 and III-C.2 show plots of RMS displacement and GA values vs percent power obtained from the pre-modification SSPB test data and plant data. A comparison of these figures shew that the plant data compare well with the SSPB full scale test data.

Figures III-C.3 and III-C.4 show similar plots of the postanodification SSPB full scale test data and plant data, respectively.

A comparison of these figures show that the post-modification plant data compare well with the SSPB full scale test data. Hence, the pre-and post-modification plant tube vibration data are consistent with the data obtained from the SSPB full scale model.

1307c/0188c/071184:5 20

.. _.. _ = _. _ - -

1 C4b,4C.

4 J

l Figure III-Col 3SPB Pre-Modification Test Data

f 4

i 4

f 1

2 Figure III-C.2 D2/D3 Fre-Modification Plant Data

s Yi4 L 1

i i

=

L Figure III-C.3 SSPB Post-Modification Test Data

-1

&,4 C-r 1

I i

4 i

1 i

e 4

4 i

/

i e

I f

l:

l-i i

Figure IIT-C.4 D2/D3 Post-Modification Plant Data 1

u l

D.

SUfHARY/ CONCLUSIONS l

Tube vibration data were collected at 5 plants equipped with model D2/D3 steam generators.

Data were collected before and after the installation of a preheater inlet manifold modification, and were recorded at power levels f

ranging from 0 to 100 percent power.

Reduction and analysis of the recorded data provide a data base foi the data summary shown in Table III-D.1, and the following observations and conclusions.

1.

The post-modification values of RMS displacement, peak-to-peak g's and GA's at 100 percent power are generally less than the corresponding pre-modification values at 50 percent power. Operating experience with the unmodified configuration indicated low wear rates at 50 percent power.

It is thus expected that the design :rodifications will result in a significant reduction in the wear rate. This has been confirmed by eddy current testing.

2.

Although tube support plate hole alignment can vary from generator to generator, the post-modification plant data show a tendency for improved tube support in addition to reduced vibration levels.(

eo.,c,e

.a 3.

Pre-and post-codification plant tube vibration data are c:;nsistent with data obtained from full scale test models.

1307c/0188c/071184:5 21

TABLE III-D.1 D2/03 POST MODIFICATION DATA

SUMMARY

Pre-Modification Data o 100 Percent Power

">'st

- Plant Data:

- SSPB Data:

o 50 Percent Power

• > C t-i

- Plant Data:

Manifold Data o SSPB 100 Percent Power S C t--

i o Plant Data 100 Percent Power (5 plants) a.,t,9-.

Conclusions o Plant data at 100 Percent Power i SSPB Manifold at 100 Percent Power i Pre-Modification Plant Data at 50 Percent Power o Instrumented tube data indicates modification objectives are met 1307c/0188c/071184:5 22

I V.

EDDY CURRENT EXAMINATION AND EVALUATION A.

Typical Pre-Modification Data Eddy current testing is typically used to inspect the heat transfer tube conditions in steam generators. Initial eddy current testing at Ringhals 3, following the tube leak indicated degradation of the tubes of Row 49, 48 and 47 on the outlet (cold leg) side of the steam generators in the preheater region. Similar results were reported at Almaraz 1.

These initial inspections were made using the differential eddy current technique.

Continued development of eddy current testing methods resulted in the technique used presently which is a combination of a differential and absolute eddy current testing method. The absolute eddy current component is used to determine the depth of indications suspected to be caused by wear, the differential eddy current assists in locating the indications and also provides an inspection of the remaining tubing for potential degradation resulting from other mechanisms.

A combined differential / absolute eddy current inspection was conducted at Ringhals 3 in March 1982.

During this inspection,1668 tubes were inspected and 799 indications were identified.

Following the inspection, the plant returned to operation limited to a 40 percent power level and operated for 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />. In June of 1982, an eddy current inspection similar to the one performed in March was conducted. A l

total of 1716 tubes were inspected and 610 indications were identified. The following table presents a summary of the inspection results.

{

i i

1307c/0188c/071184:5 - 23

O' O

Ringhals-3 ECT Inspection Sumary Inspection Item S/G 1 S/G 2 S/G 3 March 1982 Total Tubes Inspected 556 556 556 Tubes w/ indications 80 439 280 June 1982 Total Tubes Inspected 572 572 572 Tubes w/ indications 52 338 220 t

The totals of the June inspection for indications were lower than that reported in March as a result of a change in the eddy current technique used and not due to a significant change in the steam generator tubing condition.

Eddy current testing is least sensitive in detecting and estimating depth for small indications.

Sensitivity and accuracy increase as the size of the indication increases. Many of the March indications were very small and were not again detected in the June inspection due to the limited sensitivity of

~

eddy current testing for the small indicaticns.

To provide additional information on changes in tube conditions between the two inspections, eddy current signals from the Ringhals-3 March and June inspection were reviewed using a signal to signal comparison method. The selection included a sample of all size indications including zero degradation.

If indications had grown in depth, a noticeable change in the eddy current signal shapes would have taken place.

If signal shapes are similar, no measurable increase in wear has occurred.

It was concluded that no measurable growth had occurred.

The initial inspection at Almaraz 1 in November 1981, found wear as in Ringhals 3 but not as advanced in terns of number of tubes and depth.

Following this inspection, operation was limited to 50 percent power for 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />. The next eddy current inspection was performed in March of 1982, followed by operation for 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> at 50 percent power and a third inspection in July 1982.

The following table is a comparison between the March and July inspection results for indications of wall loss greater than or equal to.10 percent.

1307c/0188c/071184:5 24

ALMARAZ UNIT 1 R0W 47-49 COLD LEG MARCH 1982 - JJLY 1982 ECT COMPARISON OF INDICATIONS > 10 PERCENT ABSOLUTE S/G Row Column Plate March 1982 July 1982 Reading Number Number Nunber Abs Depth Percent Abs Depth Percent Change 1

49 54/6

<10 10 48 50/6 17 17 0

53/6 18 15

-3 54/6 20 17

-3 60/6 12

<10 2

49 68/7

<10

<10 3

49 47/6 11

<10 50/6 13 11

-2 57/6 21 23

+2 61/6 15 15 0

63/6 14 13

-1 65/6 12 11

-1 65/6 23 25

+2 68/6 15 15 0

i i

i

• Cannot ccmpute a reading change l

l

(

l l

1307c/0188c/071184:5 25

This comparison shows that little or no change was observed in the condition of the tubes between inspections. The reading changes in the table of Almaraz inspection results are within the accuracy range of normal eddy current testing, which is on the order of 10 percent.

In order to better compare tube conditions from March to July a signal to signal comparison was also made for the Almaraz 1 plant. This was accomplished in a manner similar to that for the Ringhals 3 plant. The thirty-five signals reviewed using this method indicated no change in the condition of the tubes.

The McGuire-1 Plant has Model D2 steam generators. The first in-service inspection of the steam generators was performed in March of 1982 by a Duke Power subcontractor.

Differential eddy current was performed and revealed, five indications in Steam Generator C.

Following the March 1982 inspection McGuirc-1 returned to operation, which was limited to 50 percent power with short periods of operation at 75 percent power. The next eddy current inspection was performed in June of 1982. A total of 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> were accumulated at 75 percent power. The inspection method employed was predominantly the differential method. A limited number of tubes were inspected using the absolute method. The results of the inspection are given in the following table.

l McGuire 1 ECT Data TUBES WITH INDICATIONS IN BOTH MARCH AND JUNE Eddy Current Indication (Differential Method) (Percent)

S/G C Baffle No.

March June R49 C40 6

<20 27 R49 C41 6

< 20 34 l

R49 C74 6

<20

<20 l

R49 C75 6

<20 20 R49 C76 6

<20

<<20 i

1307c/0188c/071184:S 26 i

The June inspection revealed 68 indications, occurring in all four steam 9enerators. Only 27 of the indications were due to wear. The breakdown of indications is as follows:

9 - > 20 percent wear indication 18 - < 20 percent wear indication 31 -

distorted signal 10 - PV, dent, or pilgering (Note 1)

Therefore, 27 readable wear indications were exhibited in June compared to five in March.

Note 1: PV (Permeability Variations), Dents (not occurring at a support plate), and pilgering are attributable to manufacturing.

1307c/0188c/071184:5 27

.. ~ -

-O O

B.

Post Modification Data The preheater inlet modification was completed at the Ringhals 3 plant in July 1983, in the W. B. McGuire No.1 plant in February,1983, at the V. C. Summer plant in May,1983 and at the Almaraz No.1 plant in June,1983.

Since that time, McGuire and Almaraz 1 operated approximately 6 effective full power months (EFPM) and V. C. Sunner operated for approximately 3 EFPM before shutting down for eddy current inspection of the stean generator tubes. This section addresses the results of the first eddy current inspections following operation with the modification.

Description of Eddy Current Testing The eddy current techniques enployed to inspect the tubes at all four plants were basically the same although three different testing subcontractor were employed by the utilities. At Almaraz 1, Technatom performed the inspection under Westinghouse supervision. At V. C. Sunner, the inspection was performed by Con-Am, Inc. and at McGuire 1 it was performed by Babcock and Wilcox.

Multiple-frequency eddy current techniques employing two differential and two absolute mode data channels were used in all three inspections. At Almaraz 1 and V. C. Summer, the differential data channels were operated at test frequencies of 550 kHz and 130 kHz. The differential frequencies employed at McGuire I were 400 kHz and 130 kHz.

In all three inspections the absolute test frequencies were 300 kHz and 100 kHz. The wear scar depths are analyzed from the absolute mode data.

All data was initially analyzed on-site by the inspecticn subcontractor. This same data was re-analyzed by Westinghouse Steam Generator Technology Division

.and compared to that from prior inspections to monitor the performance of the modification. The results are discussed below.

i I

1307c/0188c/071184:5 28

d Ringh al s-3 Westinghouse has not analyzed the ECT data from the last Ringhals 3 inspection. However, reports from the utility indicate that no further tube degradation has occurred since the modification.

V. C. Sumner This inspection was performed by Con-Am, Inc., who also did the on-site analysis.

No detectable wear at support plate elevations was reported.

Westinghouse re-analyzed the data from all tubes in Rows 44 through 49 in all three steam generators. The findings were consistent with those of Con-Am.

No wear was indicated at the support plate elevations in the preheater section of the steam generators.

W. B. McGuire No. 1 This inspection was performed and the initial data analyzed by B & W.

4 The results of a comparison of the 3/84 data to that obtained in 4/83 as analyzed by Westinghouse is shown in Table IV-I.

There was a slight negative change in the average wear depth in Steam Generator A, and a positive change in the remaining three steam generators. The results will be discussed in Section IV.C. Conclusions.

It is significant that no new indications were l

observed after 6 EFPM of operation.

Almaraz I j

This inspection was performed by Technatom and the data was analyzed by Zetec, Inc. The results of the comparison between 5/83 and 2/84 are shown in Table IV-II.

Steam Generator No.1 shows a slight negative change in average wear depth and steam generators No. 2 and 3 show some small positive changes.

(

Again it is significant that no new indications were observed in the 2/84 inspection.

l 1307c/0188c/071184:5 29

e TABLE IV-1 W. B. McGUIRE 1 STEAM NUMBER OF AVERAGE GENERATOR INDICATIONS CHANGE 36

- 0.67 percent A

B 1

+ 4.00 percent C

3

+ 3.33 percent D

2

+ 3.50 percent Combined 42

- 0.07 percent 1307c/0188c/071184:5 30

p.

vei TABLE IV-11 ALMARAZ STEAM NUMBER OF AVERAGE GENERATOR INDICATIONS CHANGE 1

10

- 0.20 percent 2

7

+ 1.71 percent 3

19

+ 4.32 percent Combined 36

+ 2.55 percent l

l l

l l

l:

l i

l l

l

[

1307c/0188c/071184:5 31

c.

.n..

C.

CONCLUSIONS While Tables IV-1 and IV-11 indicate an average positive change (greater thru-wall penetration) in wear depth, it is Westinghouse's judgement that there has been no significant further tube degradation. The changes in indications, when viewed relative to the repeatability of ECT from one inspection to another, are not significant. At the 300 kHz test frequency, a scatterband of + 10 percent is considered typical. At the 100 kHz test frequency, the scatter is + 15 percent. The indication changes noted are well within these scatterbands. This coupled with the fact there were no new l

indications lead to the conclusion that the changes are not indicative of further wear.

i 1

i 7

i r

i

,_._. _ 1307c/_0188_c/_0711_84 53 _ 32, _ _, _

V.

ALMARAZ PREHEATER INLET MODIFICATION VISUAL INSPECTION A.

Technical Discussion The preheater inlet modification components of the three (3) steam generators of Almaraz Unit 2 were visually inspected in March 1983 prior to operation with the modification. This inspection was performed after the feedwater piping was rewelded to the feedwater nozzle and after subsequent hydrostatic pressure testing. An industrial fiberoptic system with 35mm attachments was utilized to perform the baseline inspection.

An existing access port in the feedwater piping used for inservice inspection of piping welds provided the access required for the visual examination. The fiberoptic probe was inserted through the existing port and manuevered through one of the Reverse Flow Limiter Venturi holes to gain access to the flow splitter and manifold. By articulating the tip of the fiberscope, the desired position for observation and/or for taking photographs was obtained.

The examination concentrated on specific areas of the modification:

o Circumferential Welds (Figure V-1)

Reverse Flow Limiter to the Support Cylinder Flow Splitter to Thermal Sleeve Manifold Support Sleeve to Thermal Sleeve Manifold to Manifold Support Sleeve o

Linear Welds (Figure V-2)

Flow Splitter Vanes to the Center Post Flow Splitter Vanes to Ring 1307c/0188c/071184:5 33

a 2

a

,4-S u

.--u a

J

_- 4 x-

- A e

Aw-a a

J an.A x

n I g i=

Q,( d pp t

O e

d 4

l l

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um i

FIGURE V-1 W LD INSPECTION OF INSTALLED MAN 1FDLD

A c4d4c i

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t s

t d

4 1-i J

I A

11-i a

1

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Figure V-2 Weld Inspection of Installed Flow Splitter

l f

f'

-_.._______...._,r-._,....._._...

,,-,_m_.m--,.,_..~-,..--.,_m--,,,,.

5.

o Hardware Tapered Stud Assemblies High Strength Bolt Assemblies As-installed gap between the Flow Splitter and Manifold Entrance Plates o

Foreign Object Search At Almaraz 1, all three steam generatores had a visual inspection performed at the utilities initiative after operation. The inspection was made of the inlet modification components using the inspection port for access. The inspection was of sufficient clarity to provide assurance that no surface abnormalities existed.

1 B.

Conclusions The visual inspection described above has provided a baseline with which to compare subsequent inspection results after an intsrval of operation. On the basis of the baseline inspection, the following conclusions can be drawn:

o Fiberoptic inspection of the preheat modification components is a viable means for visual observation; o

Photographic resolution is sufficient to detect significant structural changes or surface indications;

[

o Small foreign objects / debris can be successfully retrieved through the inspection port.

o Post operation inspections may be satisfactorily performed.

1307c/0188c/071184:5 34

__