ML19308D766

Summary Rept,CR-3 Steam Generator Repair.

ML19308D766
Person / Time
Site:	Crystal River
Issue date:	08/22/1978
From:	FLORIDA POWER CORP.
To:
Shared Package
ML19308D764	List: ML19308D763 ML19308D766
References
NUDOCS 8003130769
Download: ML19308D766 (9)

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1 i SUlmARY REPORT F

CRf3 STEAM GENERATOR REPAIR

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AUGUST' 22, 1978

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Introduction and Summary This report provides the results of the Steam Generator repair effort at

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Crystal River Unit III. The report sumarizes all inspections and repairs and as such may duplicate infe mation previously provided. All repairs have been successfully completed and the unit is now available for contin-ued operation.

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Discussion of Repairs The planned repair which is now complete consisted of:

Video Inspection and Categ'orization of Tube Damage Search for Tube Leaks Installation of Shielding Installation of Screens in Lower Generator Piping

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Repair Leaks NDE Repairs and Dress Damaged Tubes 100% Free Path Check of Tubes .

,. Clean Obstructed Tubes Plug Tubes From Which Debris Cannot be Removed

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Perform a 3% Eddy Current Examination of Tubes Gas Test Repaired and Plug Welded Tubes Remove Shielding Flush Tubes Remove Screens and Close Up OTSGs The planned repair has been very successful. Video inspections from two lines of sight of the tube end damage in the "B" generator were recorded on "stop-action" discs by two television cameras mounted on a modified remote eddy current manipulator. The recordings were viewed by B&W Engineering

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personnel on a television screen providing an approximate 5X magnification.

This video inspection was used to classify the tube end damage into the following four categories:

i Class I (55% of the tubes)

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No damage or limited impact or rollover of tube ends. Defonned material

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does not include weld material.

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Class II (6% of the tubes)

Partially separated metal chip existing with Class I, III, or IV damage.

Class III (26% of the tubes)

Minor weld damage extending into the upper 1/3 of the tube-to-tubesheet weld height.

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Class IV (17% of the tubes)

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Damage to tube ends and weld metal in excess of Class III.

The above percentages exceed 100% since Class II can exist with Classes I, III, and IV.

Seventeen pieces of debris found on the tubesheet surface were removed.

The largest piece was the hub of the spider of a BPR assembly. Sixteen smaller pieces ranging from 1/8" x 1-1/4" x 3/4" to 1/8" x 1-1/2" x 21/2" were alse removed and are believed to be part of the spider arms and poison

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rod clad.

The upper manway of the "A" generator was also opened and the visual exami-

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nation revealed no debris on the upper tubesheet, no tube end damage, nor any tube-to-tubesheet weld damage. The program for this generator then consisted only of a leak detection program which found no leaks, a free path check from which no debris was. detected, and a 7% eddy current exami-natin of the tubing which resulted in no tubes with indications exceeding

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the plugging limit. One tube was plugged, however, as preventative maintenance. ,

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The leak detection program for both steam generators was similar and con-

• sisted of pressurizing the secondary side with helium gas in excess of 100 psi. A mass spectrometer capable of detecting 10-8 cc/sec leak was used to interrogate each tube end with a probe remotely positioned by the modified eddy current manipulator. No leaks in either generator were found.

' Specially designed dome shielding was installed and found to be quite suc-cessful in reducing radiation exposure. Aluminum sheets and lecd blankets were placed on the tubesheet. A special B&W designed rapid installation

dome was used to support lead blankets overhead.

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Screens were installed in the piping leading from the lower generator head so that any debris that fell down a tube could readily be caught and removed.

The tube ends were then cleaned of the partially attached slivers. Small sections of the tubesheet were exposed by removing the shielding. Person-nel were allowed to enter the upper head and slivers were removed. Two men teams were used for this operation. While one man removed the slivers, the other held a camera for remote viewing by quality assurance persennel.

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A 100% free path check of all tubes was performed. The check was performed by remotely driving a free path probe up the tube at a constant known speed with a remote probe positioner in the lower head. This special B&W de-signed fixture was developed for this free path check and subsequent eddy

' current examination of tubes with damaged upper tube ends. Again, a tele-vision camera mounted in the upper head was enployed to confirm the com-

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plated free pass of the probe. This inspection found nineteen tubes sus-pected of being blocked by debris. The final disposition of these nineteen tubes is given in Table 1.

Of the nineteen tubes, seven tubes were determined to be clear, debris was removed from five by pushing it out with a nylon coated stainless steel

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cable, and seven tubes were removed from service in order to isolate the nonremovable debris. Plugging of the tubes was accomplished by the stan-

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dard explosive tube plugging technique or a special welded plug commonly used in the B&W fabrication shops. Plug selection was based on debris location within the tbbe. This data is also included in Table 1.

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An eddy current examination was performed on three percent fo the OTSG tubes plus on those tubes from which debris was removed to give a high con-fidence level that tubes had not been damaged by debris removal or by debris that may have passed through during plant operation. This inspec-tion revealed no indications exceeding the plugging limit.

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The final stages of the repair consisted of testing the welded repairs with a gas / soap bubble test per ASME requirements, removing the shielding,

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flushing the tubes with a stream of water to remove any small particles that may have been generated during the repair, removal of the lower piping screens, and final cleaning of the upper and lower heads prior to installa-tion of hand hold and manway covers.

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Summary and Conclusions Based on the above successfully complnh d repair pro. gram and the technical

( assessments previously provided in the reference letter, it is concluded

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that the damage sustained by the OTSG will not have. a detrimental effect on its safe operation over the time remaining on this fuel cycle. This con-clusion is based on:

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1) The "hard" rolled tube-td-tubesheet joint strength is independent of the seal weld and any damage to it.

2) The minimum leak path raquired by ASME Codes has not been violated.

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3) Low cycle fatigue failures will only cause nuisance plant shutdowns for repair when leakage exceeds plant limitations.

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4) Stress corrosion cracking requires an incubation period longer than the remaining time in the first fuel cycle.

5)' Every upper tube joint has been visually inspected, catalogged; and ,

appropriately dressed.

6) Every upper tube joint has been leak tested with sophisticated mass l l

spectrometer and no leak found.

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7) A 100% free pass check of all tubes has been performed. Debris not l I

removed from tubes was isolated from the primary system by plugging the tubes.

8) A 3% eddy current examination of the tubes did not reveal any debris related damage.

9) Weld repaired and plugged tubes were gas tested per ASME requirements.

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10) The upper and lower heads were appropriately cleaned after a tube flush prior to closing up the steam generators.

The number of tubes removed from service at this outage (seven in the "B" generator and one in the "A" generator) is extremely small (less than .02%)

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and will have no effect on the existing ECCS analysis.

Reference

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1. Letter W. P. Stewart to R. W. Reid, dated May 16, 1978.

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TABLE 1 ,

j "B".0TSG: DISPOSITION OF VERIFIED DEBRIS TUBES, l -

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TUBE LOCATION DEBRIS LOCATION DEBRIS ECT FINAL R0W - TUBE DEPTH FROM TOP STATUS RESULTS DISPOSITION COMENTS -

'. 4 5 >24" REMOVED NO RETURNED TO 18" BPR INDICAT. SERVICE 6 4 24" LODGED N/A PLUGGED 9 4-1/2" ,

7 ~l >24" LOD 6t.D N/A PLUGGED 9 12'

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13 4 1/2" REMOVED NO RETURNED TO

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20" BPR INDICAT. SERVICE 19 2 FLUSl! LODGED N/A PLUGGED 9 4-1/2-6" .

22 91 4-1/2" LODGED N/A PLUGGED

, 9 4-1/2" 28 95 --

CLEAN NO RETURNED TO INDICAT. SERVICE 46 79 --

CLEAN NO RETURNED TO INDICAT. SERVICE

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47 65 --

CLEAN NO RETURNED TO INDICAT. SERVICE

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48 2 --

CLEAN NO RETURNED TO

INDICAT. SERVICE 49 2 1" ***

4 REMOVED RETURNED TO ***30 - 40% ID INDICATION BETWEEN 18" BPR SERVICE ISTH TSP AND UTS.

50 21 1" REMOVED

• NO RETURNED TO

, 24" BPR INDICAT. SERVICE i

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52 87 >24" REMOVED NO RETURNED TO

, BPR CilIP INDICAT. SERVICE 61 1 --

CLEAN NO RETURNED TO

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INDICAT. SERVICE

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TABLE I (Cont'd.) .

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, "B" OTSG: DISPOSITION OF VERIFIED DEBRIS TUBES

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TUBE LOCkTION DEBRIS LOCATION DEBRIS ECT FINAL R0W - TUBE DEPTH FROM TOP STATUS RESULTS DISPOSITION C0tNENTS

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69 24" LODGED N/A PLUGGED 9 6" 70 34 --

CLEAN *** RETURNED TO ***20% ID INDICATION BETWEEN SERVICE 13TH and 14TH TSP 82 1 7" LODGED N/A PLUGGED 9 30" 101 122 8 - 10" LODGED '/A PLUGCED 9 15' 111 64 CLEAN *** RETURNED TO

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• • • INDICATION BETWEEN SERVICE 12TH AND 13TH TSP

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