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NUCLEAR REGULATORY COLWISSION WASHlfJGTON. D. C. 20555 y
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UlW 2 91974
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I D. G. Eisenhut, Assistant Director for Operational Technology Division of Operating Reactors
SUMMARY
OF MEETING WITH REPRESENTATIVES OF WESTINGHOUSE CORPORATION ON STEAM GENERATOR TUBE SUPPORT PLATE CRACKING On the evening of May 10, 1976, Mr. V. Stello, Jr., Director, Division of Operating Reactors was informed by telephone from Mr. C. Eicheidinger of Westinghouse about the steam generator tube support plate cracking proble'm associated with Turkey Point Unit 4 and Surry Unit 2.
A staff meeting was conducted on May 11, 1976, to discuss the possible causes and safety implications of the problem. It was decided then te invite Westinghouse to make a full presentation to the staf f on May 12, 1976.
The meeting was held in Bethesda. The list of attendees and the rueeting agenda are attached.
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SUMMARY
The meeting began with brief introductions by Mr. D. G. Eisephut. of NRC and Mr. C. Eiche1dinger of Westinghouse. This was folloved by a l
description of the meeting agenda by Mr. T. M. Anderson of Wes'tinghouse.
Mr. Anderson stated that the tube support plate cracking was discovered during the course of investigating the steam generator tube denting.
i Then, he went on to summrize background information on the subject of tube denting, as provided to the staff in November and December,1975.
Mr. W. D. Fletcher of Westinghouse then proceeded to 'give an upd.:te on the Westinghouse's diagnostic programs for the tube denting phenomenon.
This presentation included a suremry of ECT and visual inspection results obtained prior to and since December,1975, to March 31, 1976, an assessment of the progression of denting phenomenon at affected operating plants, and the characterizat!on of tube leakage related to denting.
From Mr. Fletcher's presentation, we have observed the following:
1.
The denting phenomenon has been detected only in steam generators '
which have operated for a significant period of time on phosphate
. chemistry before conversion to the all volatile treatment (AVT) chemistry; 3
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"Hourglassing" of tube support plates and tube leakage associated
.<dii with denting have occurred only at the Turkey Point and Surry plants; No deuting, "hourglassing" of tube support plates, or tube leakage 3.
have been observed in steam generators which have operated only on AVT chemistry, or which utilized phosphate control only for a limited time period; 4.
Leakage associated with the tube denting has been detectable and of slow nature which allowed adequate time for plant shutdown.
Following Mr. Fletcher's presentation, Mr. A. A. Massaro of Westinghouse described the procedure utilized at Turkey Point 4 and Surry 2 to remove a sample of top plates with dented tube samples intact.
He chen presented the results of visual cbservations of support plate cracks at Surry 2 and showed photographs.taken on May 9,1976 in a Surry steam generator.
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These photographs showed the wedge area and the patch plate area of t]he top support plate.
Mr. R. T. Begley of Westinghouse Research Laboratories followed Mr. Massaro with a presentation on the preliminary findings.
of the initial investigation of the plate segment which was removed from Turkey Point 4.
He indicated that the cracks were present before the segment was removed and that, from observing the failure cross-section, the failure mechanism is duc' tile or is simply caused by over-stress. Mechanical tests of material samples made out of the removed plate segment showed no reduction of strength.
Dr. L. Conway of Westinghouse / Tampa Division then presented the results of analyses of the tube suppcrt plate under a postulated load acting radially on the ligament in the plane of the support plate.
Results tend to support Mr. Begley's observation of the ductile failure mechanism.
Dr. Conway also made an assessment on the safety implications of the
, problem. This assessment is summarized as follows:
The configuration of the tube support plate / tube bundle and the a.
corrosion mechanism leading to denting result in t]he development of-- --
compressive loads on the tubes and the plate itself. These forces tend to leck the tubes ar.d the plate firmly together even in the presence of tube support plate ligament cracking.
The presence of compressive forces and corrosion products were evidenced by the fact that very large forces were required to pull the specimens.
These compres.sive forces tend to preserve the geometry of the plate even if cracked.
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The tube support plates are primarily des?igned for purposes of fabrication and to prevent flow induced vibration of tubes in W.
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critical locations during normal operation.
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of the present condition of the support platesPreliminary evaluation and Surry 2, indicates that their original functions will
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impaired.
, at Turkey Point 4 not be Altho, ugh not _ expected to occur, loose pieces of c.
plate should not cause catastrophic tube failure eve cracked support case of postulated accident conditions.
n under worst piece of plate material sample at velocities up to 100 f /Result impacting an unpressurized tube. samples showed n t sec accident is about 70 ft/sec. maximum flow velocity that could ac o tubs failure.
The steam line break d.
The present assessment is that continued operati steam. generators will have no adverse impact on p bli on of affected
' safety.
c health and u
Following a brief caucus held by NRC staff were made by Mr. D. G. Eisenhut:
, the following statements
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The staff was in essential agreement with the a.
presented by Westinghouse,' based on the data availabl postulatcd mechanism b.
e.
e Based on the information presented, the staff did I
plate cracki.ng to be an immediate safety hazard aff not consider the health, and safety.
could continue and the start up of Turkey Point 4Therefore, the not be delayed.
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and Surry 2 should t
The staff requested that Westinghouse submit c.
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of planne,d future action.used during the. meeting as soon as possi a schedule d.
during the course of investigation of the dentiThe st
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cant findings necessary, informal technical discussions can be arr ng phenomenon.
If convenicace.
anged at mutual v-o.
l' L. C. Shao, Chief I
Engineering Branch Division *of Operating Reactors i,
Enclosures:
1 As stated i e l'
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See Next P; age i
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V. Stello, Jr., OR K. ~ Goller, OR R. Baer, OR K. V. Seyfrit, I&E L. Frank, OSD R. J. Stuart, OR W. S. Hazelton, OR M. Fairtile, OR V. Rooney, OR.
J. S. Wetmore, OR'
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C. Y., Cheng, OR V. Noonan, OR F. M. Almeter, OR B. D. Liaw, OR o
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AGENDA L.
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W/NRC MEETING - 5/12/76
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I. - Introduction
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Summary B. Update Progress of Diagnostic Programs II. M y! TSP Sample Removal A.
Removal Procedure B.
FLA/VIR Visual Findings C.
FLA/VIR Lab Exams III. Assessment of Present Conditions of S. G. at VIR & PLA A.
Tubing B.
Support Plates IV.
Safety Assessment A.
Noraal Operatiot.
B.
Accident Conditians V.
Summary A.
Action Plan / Schedule S
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M O
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A List of Attendees
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Westinghouse - NRC -- Meeting on Steam Cenerator Tube Support riate Cracking NAME.
Organization i
V. Stello NRC-DOR D. Eisenhut NRC-DOR.
V. Noonan NRC-DOR L. Shao NRC-DOR R. Stuart NRC-DOR B. Liaw NRC-DOR F. Almeter NRC-DOR R. Klecker NRC-DOR W. Hazelton NRC-DOR D. Malinowski Westinghouse /NES J. Weeks BNL T. Anderson Nestinghouse/NES A. Massaro Westinghouse /NES C. Eicheldinger Westinghouse /NEC E. Sweeney, Jr.
VEPCO D. Speide11, Jr.
. W. Collins NRC p
i C. Cheng NRC-DOR K. Seyfrit
'NRC/IE L. Frank NRC/OSD R. Baer NRC/ DOR S. Legge Westinghouse /NES D. Marburger Westinghouse /NES J. Samios Westinghouse /NES V. Rooney NRC/ DOR M. Fairtile NRC/ DOR J. Halapatz NRC/ DSS l
R..Begly Westinghouse /NES R. Longdon Westinghouse /NES Et J. Wetir; ore NRC/ ORB 3 T..
Conway Westinehouse/Tamon
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