ML19210B254

Responds to NRC 741017 Request.License Amend to Establish Program for Steam Generator Tube Insp Unnecessary

ML19210B254
Person / Time
Site:	Three Mile Island
Issue date:	11/29/1974
From:	Arnold R METROPOLITAN EDISON CO.
To:	Goller K US ATOMIC ENERGY COMMISSION (AEC)
References
GQL-0516, GQL-516, NUDOCS 7911040208
Download: ML19210B254 (5)

Text

.. T AEC DISTI':J'JTiO:: FOR i' ART 50 DCC:'ET '.* AT ER! AL .

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F RO'.1:1!etropolitan Edison Co. DATE OF COC ' D ATE REC'D LTR TV!X RPT OTr. R Reading, Penn. 19603 Mr. R.C. Arnold 11-29-74 12-3-74 Y TO: ORIG CC OTHER SENT AEC POR XXX._..

K.R. Coller 1 signed XXX SENT LOCAL PDR _ _ _ .

Ur:C L,,ES PRO? INFO ' 17.'P U T i;O CYS REC'D DCCKET ';O:

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XXX 1 50-289 El;C LO3'J F. ~ 3:

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Ler re 10-17-74.....concerning the request Reasons for determination concerning the that they submit an appi for andt to the OL subject License (tech spec) changes. .. . .

...ady that at this time they do not feel -. - - - - . _ . .

that the referenced requirements apply to I . ' / ' w N".di_.,

their Plant....and adv that should circum- (1 cy enci rec'd) stances warrant they will submit such an andt....trano the following.....

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. @ ~LUPL*L y~~h @e~gukton/ Dochet F METROPOLITAN EDISON COMPANY rc- e r s :E 3CX E*2 AE A D'NG. PI*aNST LV A*a A 000 ,

TELEPwcNE 213 - 0:0 ZO1 GQL 0516 0' N 'l.f; Mr. Karl R. Goller .g, og ,,9, Assistant Director / Operating Ecact . ,, y-Directorate of Licensing M -

r. C U. S. Atomic Energy Commissicn,94,,

Washington, D.C. 205h5 h 4,p, 5

Dear Mr. Goller:

g y-Three Mile Island Nuclear Statien, Unit 1 (TMI 1) Docket No. 50-289 ' Operating License DPE-50 In response to your letter of October 17,197h--regarding Fegulatory Guide 1.83 and your request that we submit an applicatien for a license amend-ment to establish requirements for a program of steam generator tube in-spection for TMI-l -- the purpose of this letter is to state that we have determined that it is not necessary at this time for us to have to establish such a program; and we are net, therefore, submitting an applicatien for a license amendment. Reascns for having made this determinatien are explained

 ,               in =cre detail in the attcched encicsure, and are based primarily en our conclusions that

a. elimination of the coordinated phosphate treatment method of che istry centrol vill avoid accelerated caustic stress corrosion and tube vastage,

b. strict water quality control ceasures vill prevent poor quality water from reaching the steam generators , thus serve to reduce the buildup of concentrated caustics,

c. the design of the CTSG's is such so as to minimite high stress regions, and also problems resulting fren lov flew and tube vibraticns, and

d. in light of a, b, and c above, the exposure of personnel to these kncvn high radiaticn areas for the installatien and removal of examination equipment is not warranted.

It chould be noted, however, that we do intend to follev clocely, the performance of ence-through stean generators in cur plant and other plants, and should cperaticnal or experimental evidence so warrant, ve vould, of course, establish a comprehensive inspecticn progra=. 1585 111 122r

We trust that we have sufficiently addressed your concerns regarding an inservice steam generator tube inspecticn pregram for TMI-1; and should you have any questions regarding the content of this letter, please cen-tact me. Sincerely, m R. C., Arnold Vice President RCA:DNG:eg .

Enclosure:

Discussion of Inservice Inspection -- Program for TMI-l OTSG's cc: Pennsylvania Electric Cc=pany Mr. I. R. Finfrock Vice President, Technical Jersey Central Power & Light Company 1001 Broad Street Madison Avenue at Punch Ecvl Ecad Jchnatown, Pennsylvania 15907 Merristevn, N. J. C7960 Mr. George F. Trowbridge Shaw, Pittman, Potts & Trowbridge 910 17th Street, NW Washington, DC 20006 File 20.1.1/7.7.h.3.1.1 1585 112

DISCUSSION OF INSERVICE INSPECTION PROGRAM FOR TMI 1 OTSG'S As discussed in Regulatory Guide 1.83, the prime reason for steam generator tube degradation has been the secondary side chemical environment. The prcblems that have contributed to the adverse chemical environ =ent have been sericusly considered and the design of the unit incorpcrates several features which minimize the possibility of severe chemical upset conditions and the resultant tube degradation. The chemistry used for the Three Mile Island Nuclear Station, Units 1 and 2 steam generators, is volatile in nature using hydrazine and m=nonia solutions for oxygen and pH control. This is different from the coordinated phosphate treatment previously employed 4n U-tube steam generators and eliminates the introduction of unwanted solids in the form cf sodium ions which would be free to form concentrated caustic. The inability to centrol the coordinated phosphate chemistry has been associated with the tube vastage experienced in U-tube steam generators. By eliminating this methed of chemistry centrol, the accelerated caustic stress corrosion and tube vastage should not be experi-enced. The basic design and fabrication of the once-through steam generator including the complete vessel stress relief, elbninates the high stress regions found in the U-bend area and other portions of U-tube steam generators. The straight tube-straight shell design eliminates these highly stressed bends and significantly reduces the areas of the steam. generators that vill be susceptible to the various types of corrosion. The complete steam generator stress relief reduces the residual stresses in the once-through steam generator and produces a tubing microstructure apparently more resistant to stress corrosion cracking, especially under upset conditions. The use of volatile chemistry control also reduces the builaup of sludge and scale, particularly that formed from the insoluble phosphate ecmpounds produced in the steam generaters. To prevent poor quality water from reaching the steem generator, continuous on-line monitoring is provided to assess the performance of the full flow condensate polishing unit and to detect in-leakage of air or circulating water. In the unlikely event that impurities, primarily in the form of sodium icns, silica and ferreus corrosion products, do enter the steam gen-erators, several methods of removal are available. Operaticnal procedures are established to reduce power er shutdevn when impurities entering the generator approach the recc= mended maxi =um values established by the manu-facturers. E:phasis has been placed en proper chemist"y centrol during operator training, and proper actions have been detailed in operating prc-cedures to minimize the duration of any , chemical upset. The ence-through design with superheated steam does not concentrate chemical impurities in the steam generator. The sedium and silica impurities are soluble in the superheated steam and consequently are carried cut of the steam generater if inadvertently introduced. The superheat performance of the steam gen-erator is monitcred to determine the accumulatien of impurities that are not soluble in superheated steam. When evidence of degraded superheated performance is obtained, chemical cleanin6 is performed. s 1585 i13

The design of the OTSG has also included considerations in the areas of low flew and tube vibration. These have been detailed in E&W Topical Reports on the subject. In summary, the factors which have contributed to tube degradation in the U-tube steam generators are not present in these units. Although methods are being developed to remotely examine the tubes during annual outages, the unnecessary exposure of personnel to those known high radiatien areas for the installatien and removal of the examination equipment is unwarranted. The performance of cnce-through steam generators in other plants is being followed closely to determine if any degradatien of integrity exists. A comprehensive inspection program vill be develcped at such a time that the operational er experimental evidence warrants further measures to insure steam generator tube integrity.

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