ML17341B331
| ML17341B331 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 07/31/1982 |
| From: | FLORIDA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML17341B330 | List: |
| References | |
| NUDOCS 8208160303 | |
| Download: ML17341B331 (64) | |
Text
REPORT OF STEAM GENERATOR INSPECTION AND TUBE REPAIR TURKEY POINT UNIT 4 JULY 1982 OUTAGE 8208160303 820809'DR ADOCK 0500025k
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TABLE OF CONTENTS
1.0 INTRODUCTION
- EVENT DESCRIPTION 2.0 RESULTS OF STEAN GENERATOR INSPECTION PROGRAM 2.1 Steam Generator Annulus Search 2.1.1 Preface 2.1.2 Fiberoptics 2.1. 3 Operation 2.1.4 Video Camera 2.1;5 Comparison of Techniques 2.1.6 Recent Experience at Another Plant Location 2.1.7 Determination of Visual Technique Used in Turkey Point Unit No.
4 Steam Generator 2.1.8 Results of Fiberoptics Annulus Search 2.2 Steam Generator Eddy Current Inspection Program 2.2. 1 Description of Eddy Current Inspection Program 2.2.2 Results of the Eddy Current Inspection 2.2.2.1 Eddy Current Indications 2.2.2.2 Tube Restrictions 2.3 Results of Profilometry Inspection 2.4 Review of Prior Eddy Current data for R44-C57, R44-C58 3.0 TUBE DAMAGE ASSESSNENT AND RECOMMENDED SAFEGUARDS 4.0 SAFETY EVALUATION 4.1 Continued Operation Mith Foreign Objects Present in Steam Generator 4.2 Tube Plugging APPENDICES 1.
Foreign Object Retrieval Operations Performed in'Secondary Side of Turkey Point Unit No.
- July, 1982 Outage.
2.
Description Of Metal Impact Monitoring System Applied to Turkey Point Unit No.
LIST OF FIGURES Steam Generator A Inlet - Location of Tubes Eddy Current Inspected Steam Generator A Outlet - Location of Tubes Eddy Current Inspected Steam Generator 8 Inlet - Location of Tubes Eddy Current Inspected Steam Generator B. Outlet - Location of Tubes Eddy Current Inspected Steam Generator C Inlet - Location of Tubes Eddy Cur riant Inspected Steam Generator C Outlet - Location of Tubes Eady Current Inspected Gauging Results, Steam Generator 8 Inlet.
Results of Profilometry Inspection of Tube R44-C57.
Steam Generator 8 Inlet Results of Profilometry Inspection of Tube R44-C58.
Steam Generator 8 Inlet Eddy Current Signals R44-C57 and R44-C58 Eddy Current Signals R44-C57 and R44-C58 Recommended Plugging - Steam Generator A
Recommended Plugging - Steam Generator 8
Reccmmended Plugging - Steam Generator C
LIST OF TABLES 1.
Inventory a'nd Dispostion of Foreign Objects Observed 2.
Number of Steam Generator Tubes Inspected 3.
Eddy Current Indications Reported 4.
Number of Tubes Restricting Passage of Probe Listed 5.
Eddy Current Data Analysis - Steam Generator B - Row 44C57 and C58 6.
Summary of the Damage Assessment and Recommended Sentinel Plugging 7.
Recommended Tube Plugging
0
a 1.O INTRODUCTIOH - EYE OESCRIPTION On July 6, 1982, existing primary to secondary 1 akage in agleam generator B ah Turkey Point No. 4, began to show signs of incre'sing.
Over the next approxi-mately 36 hou'rs the rate of leakage increased from about 1.2 gallons/hour to an estimated 5 to 10 gallons/hour.
Florida Power and Light Company elected to
. shut the plant down to locate and'repair the source of leakage.
After entry into the Steam Generator B was effected, the source of leakage was identified as tube R44 C57, hot leg.
Eddy current (EC) testing detected the presence of an apparent through wall penetration at the top of the tubesheet in the leaking tube.
A similar signal, unchara"terized due to its complexity, was 'detected on the adjacent tube, R44 C58, hot leg.
Since the neighboring tubes,did not exhibit dents at the top of the tubesheet, and since a similar leakage event had occurred the previous month in Steam.
Generator B at R44 C36, cold leg, a program including secondary side vi'sual inspection and selected tube EC te'sting was established.
2.0 RESULTS OF;.STEN GENERATOR INSPECTION PRO"=RAH 2.1 Steam Generator Annulus Search 2.1.1 Preface 0
The purpose of this review is to describe the 'echnique used to visually inspect and record the nature and location of certain foreign material(s) found in the secondary side of the Turkey Point Unit 4 Steam Generators.
This method was also ised to provide pictorial data for the evaluation of associated tube anomalies.
Introduction The fiberscope used by Mestinghouse for steam generator inspection is a current, "state-of-the-art" viewing device. It is a bundle of glass fibers
$ n which the light necessary for viewing travels through some of the fibers while the remainder tr ansmit the image.
A cable through the center provides a means
'of tip angulation to increase the range of view.
The apparatus is flexible and can be directed to almost any accessable location within the working length.
The equipment used for the steam generator annulus search is an Olympus 1F1193 Industrial Fiberscope; Olympus ILK-4 Light Source; and Olympus OM-1 35mm camera with fiberscope adaptor.
The fiberscope has a working length of l08 in.
and a depth of field ranging from 10am to infinity.
The field of view is 65'nd is enhanced by angulation of the viewing tip which can be turned in any direction.. This scope affords the optimum view'provided size is not a constraint.
A 35mm camera can be attached to the scope to document any viewed condition.
The best "feel " or picture of the situation is seen through the eyepiece of the operator.
2.1.3 Ojeeratfon To prepare for an inspection, the handhole covers and tube lane blocking devices are removed.
Mater on the tubesheet should be removed, The fiberscope is hand fed into the generator.
The inspector scans every tube, photographing any abnormal conditions.
A 360'nspection can be obtained through the two penetrations on opposite ends of the tube lane.
A search requires about one ten hour shift per generator, if no abnormal conditions exist.
~ S
2.1.4 Video Camera A.
Introductf on
.. The video camera system used by Mestfnghouse HSD fs made especially for dark tight areas fn a radiation ffeld. It uses a low light level camera tube which fs radiation tolerant and operated remotely
. from a control unit.
Except where constrafned by fts size (21 fn. x 1.25 fn.) the camera can reach most areas of the generator.
B.
Description At present the system fn use fs the Mestfnghouse ETV 1250 Hfnfature Underwater TV Camera.
In addition, a rfght angle rotator capable of 360'otation, and video recorder are used.
The camera has a.125 ft. cable allowing the control unit to be in a lower radiation area.
The focus range fs from 1 fn. to fnffnity lfmfted only by light which reaches approximately 16 inches above the tubesheet.
C.
Operation Scan and documentation of the steam generator require the tube lane blocking device and any water on the tubesheet be removed.
A track fs set up fn the generator bundle to shell annulus to guide the camera and a control station fs set up.
This initial preparation time is 4 shifts.
It fs anticipated that each scan would then take 4 shifts per generator.
2.1.5 Com arfson of Techni ues Fiberoptfcs fs the preferred method of fnspection whereas the video camera provides an all fnclusfve record documentatfon.
The operator of the ffberscope can obtafn a better understanding of the total conditions since the image fs three-dimensional; fs fn color; and fs quite clear with minimum
- glare, a condition whfch video has trouble controlling.
The fiberscope can
'l
look from unlimited angles and distances wher'eas the video camera cannot.
The video documentation takes about five times as long, which results in more radiation exposure to personnel.
Documentation through the fiberscope provides clearer results but 100 percent documentation would require thousands of pictures. 'onsequently, unless 100 percent documentation is necessary, fiberoptics is the preferred method.
2.1.6 Recent Ex erience at Another Plant Location The initial inspection with the fiberscope of a steam generator at another plant, where it was determined that the damage was extensive, resulted in a decision that 100 percent documentation would be required.
All efforts were therefore directed to a video camera. inspection.
Problems associated with'the video results at this site were poor lighting, glare or burnout, and lack of clarity.
2.1,7 Oetermination of Visual Techni ue Used in Turke Point Unit 4 Steam Gener ators Base'd upon the initial fiberscope inspection of Turkey Point Unit 4 Steam Generator B, it was determined that a fiberscope was the inspection equipment which would provide the optimum data for a technical evaluation of the tube anomalies.
In accordance with this determination, the fiberoptics technique was used for the visual inspection of th'e annulus region in each steam generator, and for the. photographic recording of foreign objects observed in these steam generators.
2.1.8 Results of Fiberoptics Annulus Search As a result of the fiberoptics i'nspection of the steam generator. annuli, a
number of foreign objects were observed and photographically recorded.
A list of the objects observed 'in each steam generator is provided in Table 1.'
photographic record of the objects has been prepared and has been presented in
TABLE 1 Inventory and Disposition of Foreign Objects 0bserved in Secondary Side of Turkey Point Unit No.
4 Steam Generators - July, 1982 Outage Steam Generator Size Location Position I. Weld Rod
- 2. Flat Bar
- 3. Coiled wire or strip
- 4. Coil ed Wire 8"
1 ong
]
II x 2II Very Small Mass about 1/32"xl/4" X 2" Very Small about 1"long
- Outlet, R43-44, C33 Inlet R35-36, C18 Originally R45 now unknown
/
Unknown, sighted first day of inspection only Protruding from bundle Yes Protruding from bundle'es Between Tubes No Between tubes 4B
- 1. Bolt
- 2. Flat Stock
- 3. Stainless Steel Tube..
with wing nut Pin 5.
Weld Rod 6
"Glob"
- 7. Flat Stock
- 8. Pi ece of metal/slag
- 9. Hire 10.
Deepwell Socket 0.375"x1.0" 0
5 IIx2 IIX6 II 0.375"x6" 1.0" diam x2" long 8 II l.0"
- 0. 375"xl. 5" x 2"
.5" x 1.0" Inlet, R45, C48-50 Inlet, R44-45, C53-54 Inlet, R44, C55
- Outlet, R43, C33-34 Loose on tubesheet adjacent to tubes
- Standing, adjacent to tubes Wedged on Tubesheet Between tubes Outlet, R42-43, C32-33 Between tubes Yes Yes No Yes No 0.32"xS" long Inlet, R44,C56-58 11/16" x Near manway side tube-1/2" drive lane blocking device
- Loose, on tubesheet
- Loose, on tubesheet Yes Yes
- Outlet, R42, C31-32 Hedged on Tubesheet Yes
- Outlet, R43, C32-33 Wedged at an angle Yes Inlet, R44, C57-58 Wedged between tubes Yes 4C
- 1. Pin
- 2. Meld Rod 3.
Tapered Plug
- 4. Pi ece of Metal
- 5. Mire
- 6. Hire 1" diam x 2" long 8" long
- 1. 0"xl.5" 1 ong 0.5" diam.
3/16"xlO"long App. 1/16" x 10" long Inlet, R45, CSO-54 Inlet, R45, CS4-55
- Outlet, R44, C34-3S
- Outlet, R44, C55-56 Inlet, R45,C53-54 Inlet, R45, C53-54 l
Loose on tubesheet Yes Standing between tubes Yes
- Medged, on tubesneet Yes Hedged on tubesheet Ye Located ia bundle'e Leaning into bundle Ye
~
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album form to the HRC staff at the joint NRC/Florida Power and Light Co./Westinghouse Electric Corporation meeting on the subject outage on Friday, July 23, 1982 in Bethesda, Maryland.
2.2 Steam Generator Edd Current Inspection Pro ram 2.2.1 Descr i tion of Eddy Current Ins ection Pro ram limited multifrequency eddy current inspection program was pezfozrre8 in the inlet and outlet loop of each of the three Turkey Point Unit 4 steam generators as a result of the July 1982 primary-to-secondary leakage event.
(The primary frequencies were 400Khz and 100 Khz, both in the differential mode.)
In general, the program consisted of the eddy current inspection of unplugged tubes in the periphery of the tube bundle plus additional tubes in the vicinity of observed foreign objects.
The locations of the tubes inspected in this program are shown for each leg of each steam generator in Figures 1 to 6, inclusive.
The numbers of tubes inspected are summarized in Table 2.
In
'team Generator.:,B inlet, where.the tube leak was found, the tubes were inspected through the uppermost support plate (tube support plate No. 6).
In
- addition, any tubes restricting passage of the standard 0.700-inch diameter probe for this plant were gauged with probes of successively smaller diam ter (0.650 and 0.610-inch) as required until. clearance was realized.
Additional tubes, 'surrounding those found with 0.650-inch or smaller restrictions or surrounding tubes with reported eddy current indications, were added to the original program as required.
I In Steam Generator B outlet, as well as in both legs in each of Steam Generators A and C, the tubes were inspected only through the first support
- plate, and gauging was not performed.
l
)
C TABLE 2 TURKEY POINT UNIT 4 JULY 1982 OUTAGE
,/
NUMBER OF STEAM GENERATOR TUBES INSPECTED Steam Generator Number of Tubes Inspected Extent of Ins ection A inlet A outlet 201 171 First Support Plate First Support Plate B inlet B outlet 167 106 Sixth Support Plate First Support Plate C inlet C outlet 148 163 First Support Plate First Suppor t Pl ate
K ~..-
V A
33 8
83 C
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02 9
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H H
P I ets es 2
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V LLLP U Q RRRRL t PLI V TNLLILLALLLHPSIHLASLLI I LLLIL I t LLLlLLR Sl RU SLLLLRV<TLL Ps VP Ll I I I I HI NLLS LLI LLLLLLSILI LLRLLLLLLlLlSLtINISSLLLILLLNRRNLLH SR ~ PRLJJJt L NLLL I I J JJJ JJ JJJ J J J J J J JLLLLLLLLLLLPt"HKLttLLLLLLLLLSLLLLILLI I LLI l I StILtILtlSLLLLLLLNRRLLLI L PLLI LLLLPPPR J JJ J J J JJJJJJJIXXIXLLLLLLLILHIIZIIXLLI-LILI LLPXXXZILLLlLLLILLXIXXXPLLLI-LLLLPPZXIXLLLLI-LI-LLI PHP JJJJ JJJJJJJJJIXXIXJJJ JJJJJJ JIXXXXXJJ JVJJJ JJJIZXZJJJJJJJJJJJZZXZXJJJJJJ JJ JJJZZXXJ J J JJJ JJJJJJJ
+
+
e---,NANMAY FIGURE 4
'IRKEY PODir UNIT 4 STEAM GENERA'mR 8 OUTLET NOZZLE -+
~
~
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TtA3ES Pt,VGGED 0/7dt CP 6/70 VR tL 6/00 p tICCH PI.UGGED I I/00> td.Ctt PLUGGCO I I/d!ItICCII PLV6OCD II/dl>II/It Id. ON.T SPREES FLA-L Ol UMNS
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+
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ROWS
~
NANMAY FIGURE 5
'mRXbY POINI'NIT 4 STEAM GENHN'IR C INLEf JULY, 1982 GUTAGE
DOz St 05 Ct Ot 0/7hJ TVOCS PLVOOCD e/7aI PCS PLVOOCD I/7OI T1eCS PLVO~
O/70 I TVOCS PLEAD 9/7OJ TLSCS PLl&OCD I I/7OI TM)CS PLVOOCD 1/77I T1RICS PUKOCD O/77 J TVOCS PLVCQCD h/77 J TlbCS PLVOOCD 7nrJ ~ tlCh.C ta.. re amer IOO II~
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$ >SN
- 6) Q (0 Q NR M lA LA 0 1
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00 b~'b RR RRRI 'bbb SNKNM NBT I K00000HNK KRKI bLMKblCbKbKN 000000 KMKKN KKK LKKKK StCRKbb RKL K K K HH KKK LLLF SKLKL.SKNLKILK SSKXKLSKHLKLLK KKKK NHNLLKLK KKKKNNNKLLKLKNXXXXXLKLLKKLKKH FFFFFFFFFFFFFFFFFFFFFFFFFFFFF KRKLKLBKBKKKKKBiLKKKLl 1KKKKKKRRLKKKK JXXHXLKKKKKKKKLLLKUKLLLKKKKKKHHLKKKKH FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF RKKK S
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"'9 37 36 34 32 33 31 28 29 27 26 24 22 23 21
.19 17 16 14 12 13 11 18 8
6
~
3 ROWS
+--- HANMAY FIGURE 6
'IURKIY POINT UNIT 4 STEN GENERATOR C VJI'IZl'LY 1982 QJTAGE NOZZLE -+
2.2.2 Results of e Eddy Current Ins cotton
~
2.2.2.1 Eddy Current Indications
~
'ddy Current '(wall loss) indications were observed only in Steam Generator B.
The reported indications are listed in Table 3.
TABLE 3 TURKEY POINT UNIT 4 - JULY 1982 OUTAGE EDDY CURRENT INDICATIONS REPORTED I ~
g
~
r S team Genera tor Row-Col umn Eddy Current In die ati ons El evati on B inlet B inlet B inlet 44-57 (1eaket
)
44-58 44-56 99 percent, 99 percent 56 percent Top of tubesheet Top of tubesheet 10 'bove tubesheet B outlet B outlet B outlet B outlet B outlet B outlet B outlet 42-31 42-32 43-32 43-33 43-34 41-32 41-32 29 percent 29 percent 32 percent 25 percent
. 38 percent
<20 percent
<20 percent 5" above tubesheet 5" above tubesheet 4" above tubesheet 4" above tubesheet 4" above tubesheet 25" above tubesheet 40" above tubesheet Mith the exception of the tube at R41-C32, the observed indications were at tube locations and elevations which have been correlated directly or approxi-mately with the locations of foreign objects (See Section 2.8, Table 1.)
h
~ p 2.2.2.2 Tube Restrictions Restrictions to the passage of the eddy current probe were noted in each of the steam generator loops tested.
As noted
- above, gauging with smaller-diameter
- probes, as required, was accomplished only in Steam Generator
J.
B inlet, since the eddy current inspection was initiated in this leg, where the leaker was located, prior to the availability of results of the secondary-side visual examinations.
As these results were made available and it became evident that the leak as well as other reported indications and tube damage were associated with foreign objects ob'served at or near tube sheet elevations, further EC inspections were made only in the region of interest i.e.,
up to the first tube support plate, in order to reduce unnecessary exposure.
The nunbers of tubes restricted to the various-sized probes are listed in Table 4.. The locations of the 0.650 and 0.610 inch restrictions in Steam Generator B inlet are shown in Figure 7.
2.3 Results of Profilometry Ins ection Two (2) tubes in Steam Generator B and thirteen (13 tubes in Steam Generator C were reported as possibly having bulges (detected visually or by the eddy cui rent inspection).
A special inspection of tnese tubes,'nd three (3) adjacent tubes in S/GB was performed using special probes designed to provide data on the profile of the tubes inner diameters.
The purpose of this study was to verify and map the contours and orientation of the reported bulges.
The five (5) tubes inspected by this method in Steam Generator B were the leaker (R44-C57) and four adjacent tubes (R44-C58, and R43-C55, 57, 58).
Evaluation of the profilometric data clearly shows bulges in Tub'es R44-C57 and 58, where the largest bulges were observed visually, but does not show bulges in the other three tubes in Steam Generator B.
In tube R44-C57, the maximum bulge size (inner diameter) was measured as 0.799 inches.
This is 24 mils in excess of the nominal tube I.O. of 0.775 inches.
In tube R44-C58, the maximum I.D. of the bulge was measured as 0.802,inches.
This is 27 mils in excess of the nominal tube I.D.
The orientation of the bulges was in the direction of the tube bundle periphery, where one of the foreign objects was observed lying on the tubesheet.
Plots of the resulting data for these two l
tubes along eight radii at the elevation. of the maximum bulge radius are shown in Figures 8 and 9.
A C
C.
F HIJ K
L 122I II 3
aS SQ I
3CW lU""ES PLUGGED PRIOR TO 18/75 8/75'ARE HOLE PLUG HL E/P CL SHC+ MELD 0/75q BLARE HOLE PLUGS HL,CL 5/78g TUBES PLUGGED 8/70>
'rUOES PLUGGCD II/.Op TUBES PLUGGED 7/77'ELD REPAIP.
7/77'UBCS PLUGGCD H
9 H
79 P
28 R
~
52 S
48 T
50 U
42 V
I M
5
~
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1 Or 77'TUBES PLUGGED 2 70t 'YUOES PLUI'GED 8/78:
TUBES PLUGGED I/79i TIIOCS PLUGGED 5/00p HCCH PLUGGED
'I/00>
HCCH PLUGGCD II/Ol;HCCH PLUGGED
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l ll I,'
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+
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ROWS
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+.NANMAY nmKEY FOWr UNIT 4 GAUGING. }ISULTS-JULY, 1982 TUBE RESTRICTIONS X "-.S40 PROBE M3. OF TUBES None 1
NOZZLE -+
FIGURE 7
~ ~ $
~
~
TABLE 4
. TURKEY POINT UNIT 4 JULY 1982 OUTAGE NMBER OF TUBES RESTRICTING PASSAGE OF PROBE LISTED S/G Probe Diameter Number of Restrictions A Inlet A Outlet
.700 - inch
.700 - inch 46 3
B Inlet
.700 - inch
.650 - inch
.610 - inch
.540 - inch
, 57 21 1
none B Outlet
.700 - inch 13 C Inlet C Outlet
.700 - inch
.700 - inch 28
~
~
Results of the profilometric inspection of the thirteen tubes in steam generator C selected on the basis of bulge-type signals d=-.ducted in the normal EC inspection zt the top of the tubesheet in the outl-'t leg were in:onclusive inasmuch as evidence of bulges (if present) could not be definitely established.
Tubes R4-C1; R5-C1; R7-Cl; R9-C2; R10-C2; R33-C15; f.'.2-C41, 42, 55; R43-C32, 33, 34; and R44-C37 were the locations thus identified.
2.4 Review of Prior EC Data for R44-C57 R44-C58 Table 5 provides an independent analysis of the eddy current data from Steam Generator B, R44-C57, 58.
These data encompass the period from the 1976 inspection to the present.
Also included as Figures 10 and 11 are photographs of the oscillographic display of the eddy current signals.
These data show incipient wall loss in 1977.
The 1981 and 1982 photos indicate a strong tube distortion (bulge) influence at the point of tube penetration.
~ ~ ~
e
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'IURKEY POINI'NIT 4 RESULTS OF PROFILQKKY INSPECTION OF TUBE R44-C57, STEAM GENERATOR B, MZZ
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TURKB'OINI'NIT4 RESULTS OF PROFILQKIRY INSPECTION-OF TUBE R44-C58, STEAM GYRATOR B, INLET
,r
~
~
TABLE 5 EDDY CURRENT DATA ANALYSIS STEAM GENERATOR B ROM 44 COLUMNS 57 AND 58 J
- Row 44 Column 57 April 1976 -
Some distortion of the tubesheet, but nothing to indicate loss-of-wall ot any denting or bulging.
May 1977 and April 1979 Change in distorted tubesheet signal with. some indication of loss-of-wall at and above the top of the tubesheet.
Row 44 Column 58 April 1976 - Same as R44-C57 May 1977 and April 1979
- Same as R44-C57 May 1980 July 1981 Duly 1982 Signal starts in the direction of a bulge (to right) but is rapidly drawn back to the left.
This could be caused by loss of wall in that area.
Complete saturation of the 400 Khz and the 400/100 Khz mix.
No infor-mation available other than that there is a fairly large bulge.
However, the 100 Khz signal indi-cates 60 'percent - 80 percent loss-of-wall in that area.
Same as above for 400 Khz and 400/100 Khz mix.
Phase angle of 100 Khz signal has rotated further clockwise to the thru-wall area, May 1980
- Same as R44-C57 Duly 1981 - Same as R44-C57 f 400 Khz and 400/1 mix.
The 100 Khz nal shows the pre of bulging but is torted by a verti component probabl to loss of tubew Duly 1982 - Same as R44-C57 400/100 Khz mix.
100 Khz signal i at face value wo<
an I.D. indicati However, it is b that the bulge
(
goes horizontall the right and th left) combined w
O.D. loss-of-wal (which goes down then up) has ro a real 0.0. los wall into the I.
plane.
R44C57
~
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R 44CSS V
I
e 3.0 TUBE DAMAGE ASSESSMENT AND RECOMMENDED SAFEGUARDS Peripheral tubes in both the hot-and cold-legs of all ".h-,=e steam g-:.",erators have been examined visually from the secondary side using fiberoptics as well as EC probes through, the primary side.
Additionally, profilometr~ was completed on selected tubes which appear to have bulges from the fiberscope examination.
The following assessment of tube damage is based primarily on the results of visual examination and supplemented, where applicable, by EC' and profilometry data.
The major concern with tube damage on peripheral tubes is the potential of large leakage due to:
(1}
Impact/wear damage to an active tube by a loose foreign object, and (2)
Severance near the tubesheet of a structurally degraded plugged tube and its interaction with an active tube, resu1ting eventually in a large leak due to impact/wear damage.
Based on previoa~ s experience, a tube must undergo a significant (visible) structural degradation before it could precipitate any large leak due to either of the above failure paths.
The logic to safeguard against any major tube failure is, therefore, to isolate the'ctive tube bundle from all structurally degraded tubes and loose foreign objects.
The most positive a
roach would be to physically remove all foreign objects and structurally approa unstable tubes if present (and/or segments thereof).
However, another acceptable approach would be to create a picket, fence around all identified foreign objects and str ucturally degraded tubes along with a monitoring system to forewarn of any progression of damage through the picket fence towards the active bundle, so as to assure a safe and orderly plant shutdown for any corrective action.
P
~
g I
The sentinel plug concept* fs recommended for use fn tubes forming the picket fence.
Sfnce the observed tube damage fs prfmarfly to the peripheral tubes and the faf1ure paths for a potentfal large leak are also associated mainly with these tubes, the sentinel plugs are approprfate next to the damaged perfpheral tubes only.
Any other areas of concern are recommended to be picket fenced vfth conventional (mechanfcal) plugs.
'Table 6 surmarfzes the tube damage assessment and recomnended picket tubes with sentinel plugs.
- Sentinel plugs are standard mechanical plugs with a small, built-fn leak path, fnstalled fn the unit into the inlet side of tubes not known to be damaged but located adjacent to tubes where for efgn objects were wedged, or where known tube damage had been established.
The purpose of 'these plugs fs to provide early warning in the form of controlled leakage of about 0.15
,gallon per minute, fn the unlikely event of a damaged peripheral tube severfng at the tubesheet,and damaging the neighboring tube plugged wfth the sentinel plug through impact/wear interaction, resu1ting fn a through-wall penetration of the sentinel fence.
I
w s
TABLE 6 TURKEY POINT UNIT NO. 4 STEAM GENERATOR:S
SUMMARY
OF TUBE DAMAGE ASSESSMENT AND RECOMMENDED S" 35j'INEL PLUGGING+
,/
5/G-A Tubes R43-C32, R44-C35:
.Local wear marks near tubesheet due to loose weld rod:
wear pattern about 3/8" long axially and deepest penetration may be approaching through-wall.
Both tubes are structurally stable and were previously p1ugged.
Sentinels:
R44-C36, R43-C33-36,
.R42-C33 (6 total).
2.
5/G-8 Tubes R45-C54:
. Locally indented over 3/8 to I/2" near tubesheet R44-C55-58:
Locally bulged near tubesheet, axial length, about 1/4",
maximum bul ge "30 mils.
(Profilometry on R44-C57-58 shows bulges to
'xtend over 60 to.120 degrees around circumference with maximum bulge size of 25 mils.)
R45-C53, R43-C59-61:
show polishing, peening and small ding marks.
All tubes are structurally stable and with the exception of R44-C57-.58, all were pr eviously plugged.
Sentinels:
R43-C54-58.
(5 total) 3.
5/G-C Tubes R45-C51-54, R44-C55:
Indented locally due to Impacting by a loose pin; damage somewhat more severe than R45-C54 in S/G-B, with possible thru-wall penetrations on R45-C52 and 53.
All tubes are structurally stable and were previously plugged.
Sentinel s:
R44-C50-52, R44-C54 (4 total)
- Fence is completed'by tubes plugged in previous outages and additional neighboring tubes plugged conventionally at the present outage.
Tube R44-C57 fn S/G-B was a leaker and was plugged conventionally.
o i
~
6
~
~
~
4.0 SAFETY EYALUATIOM C
S Y
~
~
~
4.1 Continued 0 eration.with Forei n Objects Present in Steam Generators I
.All three steam generators have been visually inspected on the secondary side utilizing fiber optic techniques.
These techniques allow the fnspection of the entire periphery of the tube bundle.
The inspection results have cataloged and located observable foreign objects around the periphery of the steam generators.
These objects as well as observable tube damage have been documented with photographs.
All loose objects have been removed.
Three small foreign objects still remain wedged between tubes in the bundle.
On the basis of their apparent
- mass, these objects have been assessed as presenting no potential for tube damage in the event they may become dislodged.
An eddy current inspection has been performed around the wedged foreign objects to determine the condition of the tubes adjacent to foreign objects.
A review of previous EC inspection tapes has been performed to attempt to determine if wedged foreign objects are in fact wedged and have been in their present locations for a period of time.
The following actions were taken to assure the integrity of the steam generator tubes during the next period of operation:
(a)
A conservative tube plugging program including preventive plugging and the use of sentinel plugs was developed during the foreign object retrieval operations as a contingency position in the event that the larger, more significant of these objects could not be removed.
As the r'etrieval efforts continued, all of the significant objects were successfully removed.
However, the planned plugging program has been implemented in full to maintain conservatism.
All the tubes surrounding the wedged foreign objects have been plugged and sentinel plugs have been installed a~ound potentially degraded tubes.
Sentinel plugs are standar d mechanical plugs with a small leak path built into the plug.
The sentinel I
plug will alert the operator iri the'nlikely event that a tube adjacent to potentially degraded tube'as started to leak, will limit the postulated leak and will allow the plant to respond to the situation in a normal controlled
- manner, (b) A met'al impact monitoring system has been installed on the secondary side of each steam generator as a means of detecting wedged foreign objects which may become dislodged or any additional foreign objects which may
g 4
~
0 intrude into the steam generators.
The detection of significant'mpacts will allow the plant to undergo an orderly shutdown for steam germ.'.;- inspection.
The proposed period of operation for the unit is until approximately mid-October 1982 at which time it is planned to shut down for steam generator replace.':ent.
Completion of the above actions and the short operating interval allow operation of this plant with known foreign objects in the steam generator without presenting undue risk to the health and safety of the public.
4.2
~Tb P1 ggi As a result of the eddy current and visual inspections, a number of tubes were plugged for various reasons.
In each steam generator, several tubes were considered to be pluggable due to their proximity to observed foreign objects, the presence of a bulge in the tubes, or both.
Additionally, in Steam Generator 8, the leaker (R44-C57),an adjacent tube with a 56 percent eddy current indication {R44-C54),
and three tubes with restrictions at the tube support p'fates were designated for p'iugging.
In the case of the restricted
- tubes, one was a 0.610 inch restriction, a size which had been plugged in earlier inspections in this unit, and the others were 0.650 inch restrictions, plugged conservatively because of their peripheral locations.
Sentinel plugs were installed into fifteen of the tubes, as described in 0
Sec tion 3. 0 above.
The location of the tubes plugged is shown in Figures 12, 13, and 14 for Steam Generators A, B, and C respectively.
A list of the tubes plugged, including the location of the sentinel plugs, is given in Table 7.
33 63 1
1 2
92 131 I
9/74p TUBES PLUGGED 6/7Sp TUBES PLUGGED DATE HOT KHOMMp TUBES PLUGGED StIOP MELD S/764 TUBCS PLUGGED 11/764 TUBES PLUGGED 7/77'UBES P1.UGGED 7/77'ELD REPAIR HL, E/P CL I
K L
N N
P 169 2/78p TUIIFD PLUGGED 86 ~
8/78p TUBES PLUGGED 2
~
StIOP MELD, HL ttISDRILLED 79 4/794 TUBES PLUGGED 72 S/8BI HECH PLUGGCD 27 11/89l tICCH PLUGGED 36 11/81IHECH PLUGGED SERVERS FL'A-A COLUMNS PXXOKKOXXOX0XC JO 4~
42 43 41 38 39 37 36 34 32 33 31 38
28 2627
2425 22 23 21
19'S 14 12 18 8
6 4
2 3
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+
+-MANMAY FIGURE 12
'IURKLY POINT UNIT 4 SKAM GENERA1QR A JULY, 1982 OUTAGE REC{BKNDED PLUGGING NOZZLE
t
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L
'12'I 1
3 45 QQ I
SC4 TU:-ES PLUGGED.PRZOtt TO 10/75 0/7st BAIZE HOLE PLUG HL E/P CL SHC> VELD 0/. Sp BIRC HOLE PLUGS HL,CL G/75<
TUBES PLUGGED 0/75'UBES PLUGGED Il/.dg TUBES PLUGGED 7/77/
LIELD REPAIR 7/77'IUSES PI.UGGED II 0
H 70 P
28 R
52, S
48 T
Sd U
12 Y
M 5
10/77'UBES PLUGGED 2/78g
'TUBES PLUGGED 8/70 TUBES PLUGGED 8/79'IUBCS PI.UGGED 5/80<
HECK PLUGGED
'll/00s t<ECK PI.UGGCD II/BtgKECK PLUGGED I I/Olgtt/P. tlL OIILY 0/02t tIECII PLUGGED SERZES 44 FLA-B m etpL 60 R)00
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TABLE 7
TURKEY POINT UNIT 4 JULY 1982 OUTAGE RECOMHEhDED TUBE PLUGGING The following tubes are recomnended for plugging:
Steam Generator'A":
(6 tubes)
Preventive Plugging due to proximity to foreign objects:
R42 - C33*
R43
-. C33*, 34*, 35*, 36*
R44 - C36*
Steam Generator "B ":
(25 tubes)
Preventive Plugging due to proximity to foreign objects:
R41 - C30, R42 - C31, R43 - C32, R44 - C51, R45 - C53 31, 32, 33 32, 33, 34, 35 33, 34, 54*, 55*, 56*, 57*, 58*
58 llkBLT b:
R44 - C57 Pluggin for Eddy Current Indications:
R44 - C54 (56 percent)
(*) Denotes sentinel plugs installed on the inlet side, normal plug to be installed on the outlet side of the designated tubes.
~
~1
~
RECONEISED TUBE PLVGG1NG Preventive Plu in for Restrictions:
R9-C91 R25 -
Clo'R40
- C67 Steam Generator "C":
{43 tubes)
Preventive Plugging due to presence of tube bulges or proximity to foreign objects:
R3-R4-R 5-R -
7R-R10-R11 '-
R32-R33-R41-R42-R43-C 2 C1,2 C1,2 C
1 C 2 C2,3 C 2
- C15, 16
- C15, 16 C41, 42, C41,.42, C32, 33, C37, 48, 43, 54, 55, 56 43, 54, 55, 56 34, 35, 41; 42, 43, 53, 54, 55, 56 50*, 51*, 52*, 54>>
'I
(*) Denotes sentinel plugs installed on the inlet side, normal plugs to be installed on the outlet side of the designated tubes.
II
~
APPENDIX 1
Foreign Object. Retrieval Operations Performed in Secondary Side of Turkey Point Unit No.
- July, 19".?. Outage The techniques used in retrieving the objects required the use of electro-
- magnets, horseshoe
- magnets, grabbers, electricians snake and a special tool used to move objects'out into the annulus from between the tubes.
The special tool sends a piece of banding material down the tube lane and bends it 90 to go between the tubes and ease the objects into the annulus.
Extreme care was taken when pushing the objects into the annulus to prevent damage to the tube bundle.
There is usually no contact with the tubes when retrieving objects in the annulus.
tlost of the retrieval tools are wrapped with heat shrink tubing to prevent scratching tubes.
APPENDIX 2 UNIT 4 STEAM GENERATOR LOOSE PARTS MONITOR.
DISCUSSIOH:
the steam generator MIM system is a 6 chan" 1 system.
Each channel
'consists of'
- detector, a 932 Amplifier Module and a 1432 XmpactDetector Module.
The 6 channels feed a 1433P Contxol Module and a 143'3C Audio
'onitor.
A system alarm 9.s indicated on th 133A alarm module and 'on Annunciator Panel G where the alarm 9.s combined with the Reactor Vessel Metal Impact Alarm.
Each 932 Amp19.fier module has two controls.
One sets the low pass filter upper frequency limit. It 9s normally set at 50KHZ and should not xequire any reset'ting.
The second switch determines the amplifier gain-Xt 9.s set at a value of 50 and should not r qu9re adjustment.
Higher settings will overload the amplifier as indicated.by the amplifier monitor light turn-ing from green to xed.
A lower setting ww>> reduce gain and system sensitivity.
An excessive number of spurious system ala.m can be reduced by lowering the gain setting.
Xt should however,remain at z value of at le'ast 20.
Xf the gain is adjusted to reduce the number of spurious.alarms I & C should be notified.
The 1432 Impact Detector modules have no front panel adjustments. 'he module uses a filter arrangement to establ'sh a reference background noise s9.gnal, it then looks for a transient noise signal at. a given level above background.
When this occurs, a channel a'zrt will occur and be indicated by a red light on the 1432 module.
. The 1433P control module is activated when zny of the six impact channels gives an alert.
The control module will display the number of the first channel that s9.gnals an alert.
Xt will also start a timed counter. If 5 channel alerts on a given module'occ'ur i" a 10 second period, a system alarm will occur. If 5 alerts in 10 seconcs are not detected, then the system will automat9.cally reset.
The modu e has two controls.
The alarm reset switch is used to reset a system alam. It must be'epressed to
. clear the system after an alarm condition hzs occurred.
The second switch is the Auto Reset Per9.od,Switch.
It is no~lly in the enable position.
5ihen placed in disable, it eliminates the 0 second time period requirement for a system alarm.
The 133 Alarm module has a red indicator light that indicates a system alarm and an alarm test push button.
l I
The 1433 C Audio Monitor module has a'peake='nd a selector switch that can be used to monitor the audio on any one of the six channels.
All other controls are used for an. internal test simulator and should not be used for normal system operat9.on.
A listing of channel numbers and detector locations is attached as enclosure (1).
The system sensitivity 9.s set so that it will detect a 0.048 ft-lbf impact 1 foot from the detector.
Because of this high value of sensitivity alarms can be expected during any evolut9.o" which changes the status of the plant.
An actual metal impact will be a ve~ loud metalic clank on the audio speaker.
4
STEAM GENERATOR LOOSE PARTS MONITOR DETECTOR LOCATION Channel Number 5
Location 4A S/G Lo~er Level Tap 4A S/G Tube Sheet Drain 4B S/G Lower Level Tap 4B S/G Tube Sheet Drain 4C S/G Lower Level Tap 4C S/G Tube Sheet Drain 1432 Module Label BB CC
, Enclosure (1)
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