ML18227D317

Letter Response to Request for Information on Program to Assure Integrity of Small Bend Radius Tubes in Steam Generators Which Have Experienced Denting

ML18227D317
Person / Time
Site:	Turkey Point
Issue date:	10/26/1976
From:	Robert E. Uhrig Florida Power & Light Co
To:	Lear G Office of Nuclear Reactor Regulation
References
Download: ML18227D317 (12)

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FLORIDAPOWER & LIGHTCOMPANY October 26, 1976 L-76-369 Office of Nuclear Reactor Regulation Attn:.'eorge Lear, Chief Operating Reactors Branch ¹3 Division of Operating Reactors U.

S. Nuclear Regulatory Commission Washington, D. C.

20555

Dear Mr. Lear:

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Re:

Turkey Point Units 3 and 4

Docket Nos.

50-250 and 50-251 Steam Generator Ins ection Pro ram In response to your telephone request of October 21,

1976, concerning information on our program to assure the integrity of small bend radius tubes in steam generators which have experienced "denting,"

we have prepared a program which in-volves the cooperation of three other utilities and Westing-house Electric Corporation.

The program will involve various inspections at six plant sites and is generally described in Attachment 1 to this letter.

Attachment 2 describes details of each of the inspection plans, the information to be gained, and the application of the information to the overall program.

Attachment 3 describes our detailed participation.

We will continue to keep NRC informed as information is ob-tained.

Operation will not be resumed until after NRC concurs in the corrective action to be taken.

Very truly yours, Robert E. Uhrig Vice President REU/GDW/hlc

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Norman C. Moseley, Region II Robert Lowenstein, Esq.

PEOPLE... SERVING PEOPLE

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ATTACHl1ENT 1 As a result of the evaluation of Row 1 U-bend tubes removed from Surry Steam Generator 2-A, the program of action which follows was formulated by the involved utilities with the participation of the klestinghouse Electric Corporation.

This program has three general objectives:

2.

Establish whether or not the condition is confined to Surry Unit 2.

Verify the correlation between flow slot bowing and the change in ovalization of U-bend tubes as it relates to tube conditions observed at Surry Unit 2.

3.

Define and implement a program that will assure the continued safe operation of'he affected steam generators.

The proposed program gonsists of five separate types 'of inspections with appropriate evaluation as follows:

1.

Handhole entry inspection of first tube support plate flow slots.

a.

Visual b.

Photos/TV Camera

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c.

Measurement of Flow Slots 2.

Upper bundle entry.

a.

TY Camera/Videotaping 3.

Eddy current probing in Rows 1 through 5 around U-bend to the extent possible.

4.

Drilling 3-inch access opening at the top tube support plate.

a.

Tube sample removal from Rows 1

(and if possible from Row 2) b.

Visuals/Photos c.

Measurement of Flow Slots 5.

Tube pulling (through tubesheet).

Removal of a leaky dent.

These inspections are more fully described in Attachment 2.

~EAN GENERATOR INSPECTION PRO H.

OCT.

NOV DEC FEB Tur key Point 83 Re ueling 2

3 Turkey Point ~4

, 3, 4a, 4b Surry Pl fueling 2,3,5 Surry b2 Rein pect 1 $

$ 3 Indian Point ~2 3, 4b, 4c San Onofre 1, 2, 3

1.

Hand Hole Inspection 2.

Topside Entry 3.

Eddy Current 4.

Inspection Port 3" a)

Tube sample removal b).-Visuals/photos

'c)

Measurement of flow slots 5.

Tube Pulling

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ATTACHiiENT 2 STEAtl GENERATOR U-BEND TUBE LEAKAGE OVERALL INSPECTION PROGRAM The inspections and field operations outlined in the following paragraphs are designed to provide that information necessary to answer the principal objectives of the program, viz.,

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 4:hange in ovalization of U-bend tubes as it relates to the tube conditions observed at Surry Unit 2.

3.

Define and implement a program that will assure the continued safe opera-

'tion of the affected steam generators.

The first objective will be addressed by removing U-bend samples from a steam

.generator at another site to 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, depehding upon 'the degree of distortion of the upper tube support plate flow slots, determihed for each affected steam generator.

The data obtained from the additional U-bend samples will be supplemented by eddy current examinations to the extent possible at all affected sites in order-to determine the condition of the narrow radius U-bends.

If the Surry Unit 2 coridition 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 programmed field effort, it is planned to remove a straight length of steam generator tubing that has leaked at a dented region in order to

,determine the cause of that leakage.

Any 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 maximize the opportunity for determining if the U-bend conditions are potentially generic to the affected plants.

Turkey Point Unit 4, Steam Generator 8,

has been selected since its condition appears most similar to Surry Unit 2, Steam Genera-tor A.

If the condition found at Surry Unit 2 is not found in the U-bend samples*

removed from Turkey Point Unit 4, and distortion of flow slots is. found equiva-lent 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 more steam generators must await the findings of the inspection program.

Remedial action could include consideration of additional tube plugging in a pattern designed to limit the possibility for U.-bend leakage as determined by the inspection findings.

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Oetails of the. individual inspection items are provided below:

Item 1:

HANOHOLE INSPECTIONS Access is provided into each end of the t0belane at a location between the tubesheet and the. first tube support plate.

The objective of the handhole inspection is to document the condition and dimensions of the support plate flow slots by TV videotape.

and

.photographic techniques.

These techniques have been used previously and very good results have been obtained for the first (and some-times 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 dimensions for analysis and for future reference.

Item 2:

TOPSIDE FHTAY IHSPFCTION.

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 transition cone to reach the top of the tube bundle.

Yiewing the top support plate will be attempted by inserting a small TY amera, with videotape capabilities, into the tubelane.

This re-

=quires that sufficient space be'resent between the tube bundle and the wrapper to permit entry of the TV camera and its orienta-tion down the tubelane.

If the required space is not available

" selected tubes may have to.be removed to allow the camera's entry.

. The camera will record the tube support plate condition at the flow slots and dimensions for both flow slots and tube leg spac-ing will be determined from the videotape recordings.

Item 3:

EDDY CURRENT TESTIHG

'n eddy current inspection proqram will be implemented to the extent possible, to examine all tubes in Rows 1 through 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 in-spections in passing a regular eddy current probe through small radius,U-bends.

The resulting eddy current signals have been noisy which, lends more uncertainty to the findings thin in the tube's straight length.

To overcome these difficulties, labor-atory calibration and technique refinement are presently in progress.

Item 4:

THREE-IHCH IHSPECTIOl'l PORT A three-inch inspection port will be installed in Steam Generator 8

at Turkey Point Unit 4,in steam generator A at Surry Unit 1, and in a steam generator at Indian Point Unit 2. 'hese ports will permit visual and TV videotape records to be obtained at these plants.

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At least nine tubes in Row 1 and, where practical, an equivalent number in Row 2 are planned to be removed from Turkey Point Unit 4 Steam Generator B and.Surry Unit 1 Steam Generator A for subsequent examination.

The tubes will be TIG cut just above the upper tube support plate.

This permits removal of the entire U-bend plus several inches of straight length below.the tangent point.

This same technique and -sample recovery was successfully utilized at Surry Unit 2, Steam.Generator A in Row l.

Item 5:

TUBE PULLING FOR LEAKING DFtlT (One Sample)

To address the question of what causes leakage at some dented re-gions adjacent to the tube support plate, a straight length of tubing is planned to.be removed from a steam 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 removal of this tube will be accomplished in the same manner as prior tube pulling operations.

The samole will receive extensive laboratory exam-

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ination,to determine its cause of failure.

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ATTACHMENT 3 FLORIO'OllER AND LIGHT COMPANY SPFCIFIC INSPECTION PLAN Florida Power and Light Company's specific plan for participation in the qeneral program will consist of the following:

~Tk Pi 1.

Handhole entry into steam generators A, 8, C

2.

Bundle entry into steam generators A, B, C

3.

Eddy current examination through ll-bend Row 1 - 5, steam generators A, B, C

4.

Drilling of 3" diameter access port at the top support plate on Steam Gen-erator 8 and removal of tube samples; flow slot videotaping.

~ik Pi 3

1.

Handhole entry into steam generators A, B, C

2.

Bundle entry into steam qenerators A, B, C

3.

Eddy current examination through tj-bend Rows 1 - 5, steam qenerators A, B, C

F The schedule for these items is shown on the integrated schedule provided. in Attachment l.

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