ML20040C121
| ML20040C121 | |
| Person / Time | |
|---|---|
| Site: | Indian Point, Surry, Turkey Point, Haddam Neck, San Onofre  |
| Issue date: | 12/14/1976 |
| From: | Liaw B Office of Nuclear Reactor Regulation |
| To: | Shao L Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13319A635 | List:
|
| References | |
| FOIA-81-313 NUDOCS 8201270288 | |
| Download: ML20040C121 (2) | |
Text
'
D~
0
. ENCLOSURE 2 STEAM GEERATOR U-EEND TUBE' LEAKAGE CVERALL INSPECTION PROGRAM
~
The inspections'and field op~erations outlined in the following paragraphs are desig.ed to provide that information necessary to answer the principal objectives of the program, vi=.;
1.
To establish whether or not the condition is confined to Surry Unit 2.
2.
To establish the validity of correlation between flow slot bowing and the change in ovalizatien of U-bend tubes as it rela'tes to the tube conditions observed at Surry Unit 2.
3.
Define and implement a progran that will assure the continued safe operation of the affected steam generators.
The first obj ective will be addressed by recoving U-bend sacples from a steam generator at another site t'o determine whether the tubes are in a similar condition to that found at Surry Unit 2.
If so,_
the condition will be considered as potentially generic at other affected plants, dependin'g upon the degree of distortion of the upper tube support plate flow slots, detercined for each affected. steam generator.
The data obtained freq the additional U-bend sampics will be supple-mented by eddy current examinations to the extent possible at all affected sites in order to determin'e the condition of the narrow radius U-bends.
l If the Surry Unit 2 condition is found in the additional U-bend samples, this data will add to that previously obtained to meet objective 2 above.
As part "of a program =ed field effort, it is planned to.recove a straight length of steam generator tubing that has leaked at a l
dented region in order to determine the cause of that leakage.
Any l
relationship between the U-bend conditions found at Surry Unit 2 and the leaking dented region should be established by this work.
The plant and steam generator selected for the additional U-bend samples will caxi= ire the opportunity for determining if the U-bend conditions are potentially generic to the affected plants.
Turkey Point Unit 4, Steam Generator B, has been selected since its condi-tion appears cost sicilar to Surry Unit 2, Steat Generater A.
t i
8201270288 810925 I
p c
1
-2 '
If the condition found at Surry Unit 2.is not found in the U-bend samples recoved from Turkey Point Unit 4, and distortion of flow slots is found equivalent to the distortion at Surry Unit 2, it
=ay be concluded that the condition is not generic and possibly the result of a unique condition at Surry Unit 2.
This conclusion may be supported by eddy current data analysis from other potentially affected steam generators.
Any remedial action to be taken at one or core steam generators must avait the findings of the inspection progran.
Remedial action could include consideration of additional tube plugging in a pattern designed to li=it the possibility for U-bend leakage as detercined by the inspection findings.
Details of the individual inspection items are provided belou:
Item 1:
HANDEOLE INSPECTIONS Access is provided into each end of the tubelane at a
location between the tubesheet and the first tube support
~
plate.
The objective of the handhole inspection is to 4
document the condition and dicensions of the support plate flow slots by TV vidcotape and photographic tech-niques.
These techniques have been used previcusly and very good results have been obtained for the first (and soretites second) tube support plate.
This inspection will use high intensity lighting to attempt to view higher support plates.
The dimensions of the lower plates will be correlated'with the upper support plate dimensicns for analysis and for future reference.
Item 2:
TOPSIDE EUTRY INSPECTION Topside entry provides a means for determining the condition of the upper tube support plate.
The inspection is intended to determine if distortion of
'the narrow radius U-bend tubes has occurred.
This inspection requires entry through the upper shell manway and through the transitien cone to reach the top of the tube bundle.
Viewing the top support plate will be attempted by inserting a smal? TV camera, with video-tape capabilities, into the tubelane.
This requires that sufficient. space be present between-the tube bundle and the wrapper to per=it entry of the TV camera and its orientation down the tubelane.
If the required space is not available selected tubes may have to be removed to allow the catera's entry.
The ca= era will record the tube supp'ert plate condition at the flow slots and dimensions for both flou slots.and tube leg scacing will be detercined from the videotape recordings.
C
.p
. Iten 3:
EDDY CUPS 2NT TESTING An eddy current inspection progran will be i=ple=ented to the extent possible, to exa=ine all tubes in Rows 1 thrqugh 5, through the U-bend.
This inspection would be expected to supplement other observations of the condition of the tubing in this region.
Considerable difficulty has been experienced during previous inspections in passing a regular addy current probe through small radius U-bends.
The resulting eddy current signals have been noisy which lends core uncertainty to the findings than in the tube's straight length.
To overcome these difficulties, laboratory calibration and technique refinement are presently in progress.
Ite= 4:
THREE-INCH INSPECTION PORT A three-inch inspection port will be installed in Steam Generator B at Turkey Point Unit' 4, in Steat Generator A at Surry Unit 1, and in a steam generator at Indian Point Unit 2.
These ports will permit visual and TV videotape records to be obtained at these plants.
At least nine tubes in Row 1 and, where practical, an equivalent nunber in Row 2 are planned to be recoved from Turkey Point Unit 4 Steam Generator B and Surry Unit 1 Steam Generator A for subsequent examinatien.
The tubes will be TIG cut just above the upper tube support plate.
This permits receval of the entire U-bend plus several inches of straight length below the tangent point.
This same technique and sacple recovery was successfully utilized at Surry Unit 2, l
Steam Generator A in Row 1.
Item 5: ' TUBE PULLING FOR LEAKIUC DENT (One Sample) i To address the question of what causes leakage at some dented regions adjacent to the tube support plate, c straight length of tubing is planhed to be racoved free a stean generator at Surry Unit 1.
This most likely candidate tube is in Row 3, Column 62 in the hot leg of Steam Generator A.
The recoval of this tube will be accomplished in the same canner as prior tube pulling operations.
The sacple will receive extensive labora-tory examination to determine its cause cf failure.
r O
~~
ENCLOSUPJ. 3 SOUTHERN CALIFORNIA EDISON Col?ANY SPECIFIC IMSPECTION PROGEAM Southern California Edison Conpany's specific prcgram at SanfOnofre Unit 1 for participation in the general progra= for steam generator tube inspections will consist of the following:
1.
Ha,ndhole entry into steam generators'A, B, and C 2.
Upper bundle entry into steam generators A, B, and C 3.
Eddy current examination throug. U-bend P.ows 1-5, steam generators A, B, and C The schedule for these itets is shosen on the integrated schedule provided in Attachment 1 to this Enclosure.
e U
g e
p 6
O e
e e
e e
en em O
O (3
~
Attachr.ent 1 STEAM GENERATOR INS?ECTION PROGRAM OCT NOV DEC JAN FE3 MAR Refueling Turkey Point #3 1,
2, 3 Turkey Point #4 4
1, 2, 3, 4a, 4b, 4c I.efueling Surry 61 1,
2,3,5 Reinspect Surry #2 1, 2,3 Indian Point #2 g
3, 4b, oc
.... I San Onofre p
g 1,2,3 1.
Hand Hgle Inspection 2.
Topside Entry 3.
Eddy Current 4.
Inspection Port 3" a)
Tube sacple renoval b)
Visuals / photos c)
Measurement of flow slots 5.
Tube Fulling
g..
I g
9 UNITED STAi' S g
8'
- *4 NUCLEAR REGULATORY COMM!sslON WASHINGTON, D. C. 20b5
-m'%..*..j/
a DEC 141976 MEMORANDUM FOR:
L.Shao, Chief Engineering Branch, D0R FROM:
B. D. Liaw, Engineering Branch, DOR THRU:
N R. Stuart, Section B Leader, Engineering Branch, D0R
SUBJECT:
WESTINGHOUSE PWR STEAM GENERATORS ANTI-VIBRATION BAR PROBLEM On November 17, 1976, an inspector from Region V reported through Joe Collins of I&E headquarters that, during 'the inspection of San Onofre Unit 1 steam generators, excessive wear or corrosion of anti-vibration bars was found in one of the steam generators.
A failure of these bars could result in excessive flow induced vibration that might affect tube integrity, especially for those plants where tube denting phenomenon was observed.
Our main concern was whether or not conditions in San Onofre Unit 1 steam generators may also exist in
~
Surry Units 1 & 2 Turkey Point Units 3 & 4 and Indian Point Unit 2.
Two conference calls were made on November '18,1976:
the first one was with Jerry Hanes of Southern California Edison and the second call was with Dr. L. Conway of Westinghouse / Tampa.
Items discussed in these conference calls are summarized as follows:
1.
The San Onofre Unitl steam generator A (.SG-A) was dropped during installation.
In 1973, one tube in SG-A was plugged because of excessive wear against the anti-vibration bars after ECT inspaction of about 2000 tubcc. The affected area was limited within rcus 39-44 and columns 58-64.
,.7 2.
The anti-vibration bar design of San Onofre Unit 1 and Connecticut Yankee is unique in comparision with other Westinghouse plants currently being investigated because of denting and U-bend leakage:
'a.
Materials - carbon steel for San Onofre Unit 1 and Conr.ecticut Yankee; Inconel 600 for new models (44 and 51).
b.
Bar Cross-section - 3/8 inch round. bars; changed to square bars in the new models, c.
Clearances - (L-35 mils); was changed to (L-20 mils) for new models where L is tube spacing.
d.
Changes in V-bar configuration and angular spacing.
3.
San Onofre Unit has only four support plates, compared to seven for Model 51 and six for Model 44.
Document 18 L
(
i 4.
Some hourglassing of flow slots were observed in tne lower support plate of San Onofre Unit 1.
This is significant because San Onofre Unit 1 is still on phosphate secondary water treatment.
5.
The round bars in San Onofre Unit steam generators were observed l
to thin down to 1/16 inch along the contour of tube bundle.
t 4
6.
The question on the consequence of the antivibration bar failure was not answered during both telephone calls.
The licensee will report to the Conmission about the result of their investigation in the near future.
Connecticut Yankee On November 23, 1976, Connecticut Yankee reported through W. T. Russell, ORB 1,'that tube defects were found, during ECT examinations in 1973 and 1976, in the vicinity of anti-vibration bars. As a result, two f
tubes in SG #4 and additionally one tube each in SG #1 and SG #4 were plugged in 1973 and 1976, respectively.
Conclusions From the conversations with Mr. Hanes and Dr. Conway, we were assured that conditions existing in San Onofre Unit 1 steam generators should not appear in later models of Westinghouse steam generators.
Although there is not an immediate concern over the condition of anti-vibration bars, we believe it to be prudent to have an eddy current inspection of tubes in the'U-bend region to detect possible indications of tube fretting against the anti-vibration bars in other plants which have experienced tube denting and support plate hourglassing.
Upon reviewing the safety evaluatica of the San Onofre Unit 1 inspection results and tabsequent modifications, if any, shall determine if any ramificativns of the anti-vibratior. bar problem exist at Connecticut Yankee.
hL'f
)-
B. D. Liaw Engineering Branch Division of Operating Reactors cc:
V. Stello, Jr., D0R D. Eisenhut, OT K. Goller, OR R. Stuart OT M. Fairtile, OR D. Elliott, OR P.
ickson, OR urger, OR W. Russell, OR F. Almeter, OT
/
--