ML19305D212

Summary of 800212 Meeting W/Util & Westinghouse at Forest Hills Lab Re Results of Facility Steam Generator Insp.Insp & Plugging of Steam Generators Was Acceptable & Supports Resumption of Power Operation.Supporting Matls Encl

ML19305D212
Person / Time
Site:	Prairie Island
Issue date:	03/20/1980
From:	Grotenhuis M Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
Shared Package
ML19305D213	List: ML19305D212 ML19305D215 ML19305D218
References
NUDOCS 8004140199
Download: ML19305D212 (17)

Text

' I cTAc Meeting Summary for Prairie Island 2 NARCH

o ;ggg Docket Files Gerald Charnoff, Esquire NRC PDR Shaw, Pittman, Potts and Trowbridge Local POR 1800 M Street, N.W.

OPbl Readin9 Washington, D. C.

20036 NRR Readin9 "f"

Ms. Terry Hoffman Executive Director D. Eisenhut Minnesota Pollution Control Agency R. Tedesco 1935 W. County Road B2 f,f"es Roseville, Minnesota 55113 W. Gammill The Environmental Conservation Library L. Shao Minneapolis Public Library J. Miller 300 Nicollet Mall f J.

Minneap lis, Minnesota 55401 YU r

ter A. Schwencer Mr. F. P. Tierney, Plant Manager D. Ziemann Prairie Island Nuclear Generating Plant P. Check Northern States Power Company G. Lainas Route 2 D. Crutchfield Welch, Minnesota 55089

8. Grimes T. Ippolito Joclyn F. Olson, Esquire R. Reid Special Assistant Attorney General V. Noonan Minnesota Pollution Control Agency G. Knighton 1935 W. County Road B2 D. Brinkman Roseville, Minnesota 55113 Project Manager OtLU Robert L. Nybo, Jr., Chairman 01&E (3)

Minnesota-Wisconsin Boundary Area C. Parrish/P. Kreutzer Comission ACRS (16) 619 Second Street NRC Participants Hudson, Wisconsin 54016 NSIC TERA Clarence D. Fierabend Licensee Resident Inspector Short Service List Prairie Island Nuclear Generating Plant U. S. Nuclear Regulatory Comission P. O. Box 374 Red Wing, Minnesota 55066 l

l 8004140(qq

gkB RfCg o

UNITED STATES g

8 NUCLEAR REGULATORY COMMISSION g;

WASHINGTON. D. C. 20655

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/

NARCH 2, o uso Docket No: 50-306 Licensee:

Northern States Power Company (NSP)

Facility:

Prairie Island Nuclear Generating Plant Unit No. 2 (Unit 2)

Summary of Meeting Held on February 12, 1980 to Discuss the January 1980 Unit 2 Steam Generator Tube Inspection.

On February 12, 1980 representatives of NSP, NRC and Westinghouse (W) met at the W Forest Hills Laboratory to discuss the results of the Unit 2 steam generator inspection.

Attendees are listed in Attachment 1.

Background

On January 10, 1980 NSP issued R0-80-3 which notified the NRC that a defect had been found in a tube on the hot leg side of steam generator 21 (SG 21) during a routine inspection while Unit 2 was being refueled.

On January 15, 1980 a supplement to R0-80-3 was issued indicating that additional defects had been found on the cold leg side of SG 21 and SG 22.

These defects were generally located on the periphery of the SG's at the first and second tube support plate.

An eddy current inspection was performed on all the peripheral tubes on the cold leg side of each SG.

The inspection was expanded into the center of the tube bundle until no further tube degradation was observed.

The defect in the tube on the hot leg side of SG 21 was attributed to an improperly installed tube lane blocking device.

The cause of the defects on the cold leg side of SG 21 and SG 22 could not be identified at that time.

A tube was removed from the cold leg side of SG 22 and taken to the W Forest Hills Laboratory for both non-destructive and destructive examinations.

The purpose of this meeting was to discuss the results of the SG inspection.

The l

agenda for the meeting is given in Attachment 2.

Unit 2 has been operated with an all volatile secondary water chemistry treatment system since startup.

The demineralizer has been operating on a non-continuous basis since December 1977.

Generally it was operated during startup, testing and after modifications.

The SG's were very clean and the chemistry records indicated that the water had a high purity record.

Sludge l

lancing was performed regularly.

I Twenty of the tubes examined in the most recent inspection were also examined in the last inspection in 1976.

Six of these tubes had an indication

. of defects during this inspection, whereas no indications were observed in these tubes in the 1976 inspection.

Summary The meeting was opened with introductory remarks and a discussion of agenda item I, Tube Wear Caused by Blocking Device and Corrective Action, by Mr. Watzl (NSP).

Mr. Watz1 explained that after studying the tube lane blocking device and the location of the defect, NSP and W concluded that the defect in tube on the hot leg side of SG 21 was due to improper installation of the tube lane blocking device.

Corrections applied to prevent recurrence of this problem are as follows:

1.

The installation procedure for the tube lane blocking device has been modified and verification that the installation is proper is provided by the QC department.

2.

The tube lane blocking devices were modified to include a bolt that will I

assure a proper tight fit.

3.

Tubes that are near the tube lane blocking device have been preventively plugged.

On the basis of the above remedial actions NSP concluded that this kind of problem would not occur in the future.

Agenda item II, Cold leg, Peripheral tube findings, was discussed in a presentation by the W staff.

A summary of the eddy current inspection results was given and (see attachment 3) an illustration was presented showing the area inspected and the defective tubes.

(See Attachments 4 and 5).

In order to understand the cause of the defects on the cold leg side of the SG's tube R34 C79 from the cold leg side of SG 22 was removed for non-destructive and destructive tests.

This tube had a 45% defect at the second tube support plate.

Results of the inspection of this tube are given in figures (1 through 5).

A summary of the test results from other W plants that had cold leg side tube defects is given in attachment 7.

Briefly, the conclusions reached by W are:

1.

These defects were not due to intergranular attack.

2.

There was no evidence of increased cold work due to wear, fretting, vibration, etc.

3.

Defect areas appeared free of gross deposits.

Swirl patterns were noted I

and nearby pits were observed.

4.

Some chemicals were found as noted in attachment 8.

These tests are

[

continuing.

. A summary discussion on the possible cause of the defects indicated that there was no evidence of vibration fretting, no hardness increase and no evidence of cold work.

It was believed to be corrosion due to local concentra-tion of resin fines at the tube support plate.

Similar cold leg indications have been found in the Takahoma Unit 1 plant although not due to the same corrodent.

The thinned surfaces were clean and therefore, the cause is presumed to be a dissolved corrodent rather than particulate.

Safety considerations were presented by Mr. Hirst (W).

Ar outline of his presentations is given in attachment 9 (ten pages).

He conc'wded that:

1.

Adequate burst strength is maintained for the type of defects observed, even if through wall.

Leak before burst criteria remains valid.

2.

Corrosion rate was 1.8% per month based on postulated corrosion mechanism inc alving resin fines.

3.

The safe operating interval was 16 months.

Consideration of future actions was given by Mr. Fletcher (W).

These include chemistry surveillance which would be closely monitored, particularly during low power tests.

Some sulphate and other tests would be continued in the future.

The chemical tests would also be applied to Unit 1.

Mr. Krumpos, NSP, concluded by summing up the future inspection plans for the next refueling in about January 1981.

The inspection would follow the Technical Specifications (Regulatory Guide 1.83) and would include hot leg, wedge, U-bend, cold leg, all previous indications and the tubes surrounding them.

The next inspection of Unit 1 steam generators will take into account the findinns in this inspection of Unit 2.

A similar inspection plan would be a,nplied to the Unit 1 SG during the coming fall outage.

Consideration is being given to removing the demineralizer or at least minimizing the startup and shutdown cycles which introduced more resin fines into the systems.

The above areas were presented by the NSP and W staff.

The presentation allowed for questions by the staff until all questions were answered.

Following the presentations the staff met separately to summarize and prepare conclusions.

The staff conclusions were as follows:

1.

The inspection and plugging of the SG's was acceptable and supports a resumption of power operation of Unit 2.

2.

The accident analysis was acceptable as a basis to support resumption of power operation.

3.

The presentations by NSP & W should be documented and R0-80-3 should be l

supplemented in about three weeks to include the latest results.

l l

4.

The additional data from the continuing W study should be submitted in i

about three months.

. 5.

The allowable SG leakage rate for the Prairie Island Plant Unit Nos. 1 and 2 should be modified to meet the requirements of the standard Technical Specifications of 500 gpd per steam generator (attachment 10 pages 3/4 4-17, 3/4 4-13, 83/4 4-3 and B3/4 4-4).

6.

The secondary chemistry monitoring program presented by NSP in their application dated November 22, 1978 is acceptable.

7.

Based on the above, there is adequate technical justification to support l

a return to power operation.

8.

The staff defers any conclusion regarding the acceptability of the proposed 12 month operating interval pending our evaluation of the final report (item 3 above) and future operating experience.

t y,[ucIa"

/

. Irotenhuis /

Senior Project' Manager Operating Reactors Branch No. 1 Division of Operating Reactors cc: w/ enclosure l

I

P Attachement 1 Attendance M. Grotenhuis NRC B. D. Liaw NRC C. W. Hirst W-NTD P. J. Krumpos NSP G. H. Niels NSP E. Watzl NSP R. Kelly W

J. Strosnider NRC l

E. L. Murphy NRC R. G. Aspden WR+D l

W. R. Utley W-NC0D Dan Malinowski 9 NTD W. D. Fletcher W NTD A. W. Klein 9 NTD C. W. Rowland W NSD J. C. Hayood 9 NTD j

A. Baum W NTD T. Timmons W NTD A. J. Baum 9 NTD E. P. Morgan 9 NTD F. Almeter NRC J. Weeks BNL r

b P

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NORTHERN STATES PDWER COMPANY - NRC MEETING FEBRUARY 12. 1980 Westinghouse Forest Hills Site INTRODUCTION: NSP l.

Tube Wear Caused by Blocking Device and Corrective Action.

E. Watz1 11 Cold-leg, Peripheral Tube Findings a.

Review In-Plant inspection Findings D. D. Malinowski b.

Tube Pull & Lab Examination R. G. Aspden c.

Summary A. W. Klein

- Cause

- Rate d.

Safety Considerations C. W. Hirst NSP/ Westinghouse e.

Future Actions

- Chemistry Surveillance

- Inspection Plans i

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/LWAnf 3 PRAIRIE ISLAND #2 STEAM GENERATOR INSPECTIONS JANUARY, 1980 SG #21 SG #22 u INLET Tubes inspecte'd e

thru U-bend (720 mil probe) 345 345 e

thru U-bend (540 mil probe) 63 90 e

e thru #7 Support Plate 92 92 e thru #1 Support Plate 75 e Indications Reported 1

0 e OUTLET e Tubes inspected thru U-bend (540 mII probe) 27 0

e e thru #3 Support Plate 466 934 e thru #7 Support Plate 257 213 e Indications Reported E 20% Eddy Current Indications 30 37 o

< 20% Eddy Current Indications 30 54 e

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4

&L4 *1 SURVEY OF WESTINGHOUSE OPERATING PLANTS COLD LEG STEAM GENERATOR EC DATA 3 20 I

o Plants reporting TSP elevation tube wastage:

MlHAMA #2 1/75 5 tubes

• TAKAHAMA #1 12/75 8 tubes GINNA 2/79 (3/75) 2 tubes y1 PRAIRIE ISLAND #2 1/80

&t' tubes ROBINSON #2 11/75 3 tubes i

Tube pulls at Mihama #2 and Takahama #1 Indicated PO4 wastage e

Findings at Robinson #2 and Ginna were following periods of P0 3 usage e

and during first examinations of the Cold Leg areas where the Indications existed.

PO4 wastage is the probable cause since no riew o

Indications have been found since that time No other plants have reported Cold Leg wastage in the absence of PO4 e

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SUMMARY

OF METALLtlRGICAL EXAMINATION Obs.

1. 1

1. 2

1. 4

1. 6

1. 7 TSP WALL REDUCTION LVDT 9 mils 22 mils None Nonc X-ray Thinning Thinning Micrometer 10 mils 20 mils Metallography 7 5 mils 25 mils None Nonc OD suface at wall thinned location of TSP Nos. I and 2.

1.

No intergranular attack was present.

No evidence for increased cold work at surface; based on metattography 2.

and microbardness readings.

3 Arcas were f ree of gross deposits, frequently contain swirls, and have pits nearby.

4.

Deposi ts in and near wall thinned area contain Na, P, AI, Si, Ca, S, Cl, K, Ti, Mg, Hi, Cr, Fe.

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