ML20084H201
| ML20084H201 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 06/16/1970 |
| From: | Finfrock I JERSEY CENTRAL POWER & LIGHT CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084H205 | List: |
| References | |
| 0299, 299, NUDOCS 8305020101 | |
| Download: ML20084H201 (4) | |
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M ADi$oN AVENUE AT PUNCH BOWL Ro AD e MoRRISToWN, N.J. 07960 e 539 6111 i'
June 16, 1970' 91
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Dr. Peter A. Morric Q>
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Director j
i Division of Reactor Licencing l
United Staten Atomic Energy Commiccion l
Washington, D. C.
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Dear Dr. Morris:
1 Re:
Oycter. Creek Unit No.1 1
Docket No. 50-219 Inspection of Reactor Veccel Nozzles In the summer-and full of 15'68, all nozzles in the Oyster Creek reactor veccel, which contained furnace censitized auctenitic stainlecc steel cafe ends, were modified to eliminate the cenuitized material or to clad the incide and outside surfaces of the furnace concitized cafe ends with nonsensitized Type 308L ctuinlecosteeland/orInconelveldmetal. The censitized stainleco steel reactor vencel head nozzles were replaced with nonsensitized stainleco steel.
l In April 1970, the Oycter Creek Station van shut down for examination and maintenance of the control rod drive mechanismo. In view of the core apray l
nozzle cracking problems encountered at the Nine Mile Point Nuclear Station,
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it van decided to perform visual and liquid penetrant examinations of the' outside curfacco of the Oyster Creek core spray nozzlea during thic outage.
- Accordingly, during the latter part of April 1970, the thermal insulation was removed from the north and couth core spray nozzles to permit accesc for examination.
O-The purpoce of thic letter ic.to present the results of these examinations and c
to deceribe the action taken ac.a result 'of several veld defects found in' the M-north core spray nozzle veld overlay cladding. A summary of additional exam-
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inntions and review of analyces relative to the core spray piping in also precented.
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The outsido curfacco of the couth core spray nozzle were examined visually and.
-by the liquid penetrant technique. The area examined included the-veld overlay.
6' that vac deposited over the remaining sensitized stainless steel cafe end and
.the expo'ced portion of replacement cafo end between the veld-over nd the e.
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Jnne 16, 1970 i
field weld joining the nozzle to the piping. The liquid penetrant examination was performed by a qualified General Public Utilities Corporation examiner ucing a liquid penetrant procedure that meets the requirements of Section III of the ASME Boiler and Preocure Vessel Code. The liquid penetrant examinution choved two indications in the weld overlay cladding that were of questionable relevancy due to the as-welded curface condition of the veld overlay deposit.
As a result, thece areas were polished by grinding to determine if they were a result of curface condition or were defect indications. Re-examination indicated they were not relevant defect indications and the surfaces examined
- met ASME Code,Section III, Acceptance Standards.
Subsequent to the incpection of the couth core spray nozzle, the north core spray nozzle wuc prepared for liquid penetrant examination.
In order to insure that the curface of the as-welded cladding would be cufficiently amooth to obtain an interpretable penetrant examination, the veld overlay was ground to eliminate surface roughness and crevicca between weld beads. The nozzle was then liquid penetrant examined in the same manner and ucing the same procedure ac described above for the couth core cpray nozzle. The results of this exam-inntion showed a number of relatively isolated, acceptable rounded and pinpoint indications of weld porosity (estimated to be less than 1/32" in diameter) and several lfncar indicationc. The linear indications were approximately 1/16-to 1/8-inch in length, were randomly oriented and were located primarily in the last 1/2-to 1-inch of weld overlay on the outboard (piping) side of the cladding. All were located in cladding over the noncencitized stainless steel replacement safe end. No indications were found in vroucht material or in the shop or field welda that join the piping, safe end and nozzle.
Several of the indicationc in the lower half of the safe end overlay (at approximately 6 o' clock looking toward the reactor veccel) were ground to a depth of 1/16-to 1/8-inch over an area approximately 1/2-inch wide and 2 inches in circua rerential extent.
Re-examination by liquid penetrant showed that the linear indications had not been removed. Based on the results of these examinations, further grinding of the north core spray nozzle overlay was deferred pending evaluation to determine the nature of the defecto.
On May 1,1970, a " bout cumple" was removed from the north core spray nozzle cladding for metallurgical examination. The cample was approximate 3y 1/8-inch in depth and 1 inch in length and was removed from a location in the outermost edge 01 the cladding where severall_incar indications were detected. The sample was mounted, croca sectioned and examined metallurgically by GE-APED. Based on the results of these metallurgical investigations, GE concluded the following:
1.
The obcerved defects are located in Inconel weld metal.
f.ThecracksareInconelweldfissuresorhottearsthatoccurduring 2
weld colidification. Many of the fissures do not communicate with i
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the surface.
3 There is no indication of stress corrosion attack.
Results of,these examinations were reviewed by Mr. Robert D.-Wylie, Southwest Reccarch Institute, and MPR Associates representatives who concurred in the above conclusions.
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Dr. Peter A. Morric b Page 3 June 16, 1970 i
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As a recult of the liquid penetrant and metallurgical examinationc of the core l
cpray nozzlec, it wac considered prudent to perfom additional examin,ationc of o
l other nozzlec having Inconel clad cafe ends to detemine if there is any indica-l tion of a general Inconel. weld cracking problem. For this purpoce the control l
rod drive hydraulic return line nozzle (which is clad with Inconelh and the two icolation condencer nozzlec (which are clad with both Inconel and Type 308L l
ctuinlecc steel) were colected. Liquid penetrant examinationo performed l
ucing the came procedure ac uced on the core spray nozzlec, but without prior l
curface grinding, revealed no relevant indications on the CRD hydraulic return j
l nozzle or the two icolation condencer nozzles.
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Based on the results of the metallurgical and liquid penetrant examinations, l
which indicate no evidence of streco corrosion attack or general Inconel weld l
ficcure problenc, the following action was taken to repair the cladding defects l
in the north core upray nozzle:
l 1.
A dimencional inspection of the nozzle, cladding and cafe end con-figuration was made prior to additional grinding.
2.
Indicationc of defects were removed by grinding, all cavities blended cmoothly into the contour of the surface and the final curface examined by the liquid penetrant technique. This liquid penetrant l
examination was alco perfomed by a qualified Generr-.1 Public Utilities Corporation examiner using a liquid penetraht procedure that meets the requirements of Section III of the ASLE Boiler and Precoure i
Veccel Code and it showed no relevant indications.
l 3
Thickneca und dimencional measurements were taken to accure that the mininum specified wall thicknesc remainc and that no concitized ctainlecc cteel is exposed.
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In addition to the above examinations of the' core spray nozzlec, the themal expannton and weight induced streco calculations that were performed by Burno l
and Roe, Tne., during the piping system design phase of the Oycter Creek Station
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construction have been checked by the General Electric Company and by GPU l
Nuclear Power Activities Group engineering personnel, and it has been deter-l mined that they are accurate. These streca levels are low (less than 3000 pai) and precent no problem in terms of potentially exceeding allowable strecc valu cc. Furthemore, a visual incpection hac been made of both core spray loop pipe supportc and rectrainto and no irregularities were observed.
Strecc calculationc performed by the reactor veccel manufacturer (Combustion Engineering) for the core spray nozzle cafe ends were also reviewed by General Electric to confim that the as-repaired configuration meetc original and current code standards for both internal preocure and piping loads.
L It ic recognized, as a recult of thece examinations, that the overlay cladding on the outaide of,the core opray and CRD hydraulic return nozzles differs from that deceribed in' Amendments 40 and 43 of the License Application. These
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amendmento indicate that the cladding over the cens.*ized portion of the stain-loca steel cafe end would be 308L stainlecc steel and Inconcl; whereac, examina-tion has revealed that the entire clad overlay ic Inconel. This change has
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sj Dr. Peter A. Morrio Page 4 June 16, l'7(0 m
been reviewed by the Plant Operationc Review Committee and the General Office Review Board.
Ginee the general repair procedurec precented in the above retendnento do provido for the uce of Ineonel ac a weld overIny on stainlecc cteel und it hoc been determined thic cladding was inctalled in accordance with a written field inctruction ucing a qualified welding proecdure, it hna been concluded thic change does not involve an unreviewed cafety question.
Exonination of t he reactor coolant cyctem will be continued at the first re-fueling outage (poicou curtain removal) or at an earlier date in the event conditionc amenable to cuch examinationa exist.
Very truly youro, o
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p V(lf' Ivan R. Finf' ek, Jr.
Manager of Nuclear Generating Stationc IhF/Je 9
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