ML19261F268

RO on 740402:during Check of Penetration Pressurization Sys, Leak Detected in One of Four Air Coolers in Penetration 112 for a Main Steam Line.Tubing Disconnected & Plugged

ML19261F268
Person / Time
Site:	Three Mile Island
Issue date:	04/05/1974
From:	John Miller METROPOLITAN EDISON CO.
To:
References
NUDOCS 7910250709
Download: ML19261F268 (5)

Text

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CONTROL NO: 3055 (TDiPCRARY FCRM)

• FILE: /d DATE OF DOC DATE REC'D LTR M.W 0 RPT OTHER PROM:

Metropolitan Edison Company Reading, Pa. 4-5-74 4-S-74 X J. G. Miller ORIG CC OTHER SENT AEC PDR XXX TO: SENT LOCAL PDR W A. Giambusso 1 signed INPUT NO CYS REC'D DOCKET NO: CLASS UNCLASS PROP IITIO 1 50-239 XXX ENCLOSURES: DESCRIPTION:

Attachment:

Alternatives for correcting leakin; Ltr furn infc re abnormal occurrence of 4-2-74 air cooler deficiency in main in which, during a check of the penetration stream penetration 112.. 4-4-74 pressurization pystem a leak in one of the four air coolers was detected and trans the followici .D0 NOT REMOVE ACKNOWLEDGED PLANT NM I: THREE MILE ISLAND UNIT #1 (1 cy att rec'd) FOR ACTION /I!TFORMATION 4-10-74 GMC BUTLER (L) /SC3iENCER(L) ZIDiANN(L) REGAN(E) W/ Copies W/7 Copies W/ Copier W/ Copies CLARK (L) STOLZ(L) DICKER (E) W/ Copies W/ Copies W/ Copies W/ Copies GOLLER(L) VASSALLO(L) KNIGHICN(E) W/ Ccpics W/ Coplas W/ Copies W/ Copies KNIEL(L) SCHDiEL(L) YOUNGBLOOD(E) W/ Copies W/ Copies W/ Copies W/ Copies INTERNAL DISTRIBUTION TECH REVIEW DENTON A/T IND fpr G FILP LIC ASST BRAIIMAN w m rDR /HENDRIE GRIMES GAFMILL SALIZMAN OGC, ROCM P-506A SCHROEDER DIGGS (7.) B. HURT

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                                                                   . r. e                      April 5, 197h W^'II' '      k 1-!r. A. Giambusso                                                          -

AMS jg 3 Deputy Director for Reactor Projects -g Directorate of Licensing . Office of Regulation , U. S. Atomic Energy Ccamission a ,, Washingtcn, D. C. 205h5 :s

Subject:

Three Mile Island Nuclear Station - Unit 1 g4 EM # Q[9j Docket No. 50-269 Q# ' MainSteamPenetrationDesignModificatiofg d m %9% W. (A) Alternatives for Correcting

Enclosure:

Leaking Air "coler Deficiency ]A p {$

Dear Mr. Gia=busso:

b g g On April 2,197h, a condition developed which may be censide red reportable under 10 CFR 50 55(e). During a check of the penetration pressurization system a leak in one of the four air coolers installed in penetraticn No. 112 for the "A" main steam line was detected. Description of Incident The plant was in a cold shutdevn status. Final preparations were underway for loading fuel. Du-ing a check of the penetration pressurization system on April 2, 197h, it was noted that the air flew through the "3" manifold was abnormally high and an inspecticn was initiated to determine the source of the leak. The penetration pressurizaticn system "B" manifold supplies air to five penetrations, each of which is equipped with an isolation valve. Closure of all five penetration pressurization system isolation valves terminated the excess air flow through the manifold. Thereafter, by individually cycling each valve in turn, it was determined that penetration 112 was responsible for the high flov demand on the "3" manifold. The penetration pressurization tubing to penetration 112 was then disconnected at the penetration and plugged. Upon opening the supply valve, no demand was placed on the "B" manifold, thereby proving the tightness of the tubing. The penetration pressurization system tubing to penetration 112 was then reconnected and pressuri:2 tion air flow reestablished. The penetration was checked on both sides without detection of any external leaks. It was concluded, therefore, that the penetration cooler was the scurce of the leak. 148 fh ~ ~ ~ uvaa

Sfr. A. Giambusso Fage 2 April 5,197h Since penetration 112 is provided with fcur coolers around the circumference, further testing was pursued to icolate the leaking cooler. The penetration ecoling lines from all four ecolers were disconnected and capped. By individually cycling the penetration cooling supply valves, it was determined that the lover left cooler (when facing the devnstream end of the penetration) was the source of the leak. Consideration of Alternative Corrective Action In view of the above, we have considered the alternatives available to provide the necessary integrity of the containment. These alternatives are as follows:

1. Removal and repair of the leaking penetration eccler which vculd require cutting at least vo 2h" main steam line velds and an 8" main steam dump line. The 2h" sain steam line velds at the penetration are safety related, have passed all testing requirements including hot functional testing, and are included in our Tech Specs as velds to be periodically tested in our inservice inspection program.

2. Incorporation of a design modification which would result in plugging the penetration pressurization system to penetration 112 cnly. No other changes in the penetration pressurization system would be made, the remaining 128 pressurized penetrations (which have been installed, tested, and are opera-tional) being unaffected by this modification.

Evaluation of Alternative Corrective Action and Safety Inclications In evaluating these two alternatives, we have considered the results of the recently completed reactor buildins integrated leak rate test. The initial reactor building integrated leak rate test was completed satisfactorily in March 197h without benefit of the penetration pressurization system, the system having been inactivated during leak rate testing. The resultant reactor building leak rate of 0.051% per day at design pressure of 55 psig was signi-ficantly below the maximum allevable leak rate of 0.0755 With regard to alternative 1 above, i.e., the removal and repair of the leaking cooler, in order to reestablish penetration pressurization, we have concluded that the benefits of repair do not justify the risks. The ncn-safeguard, non-single failure, and, therefore, superfluous prescurization system has already been proven nonessential during integrated leak rate testing. We can not justify the ripout of proven main steam line velds and the risks inherent in attempting to reestablish main steam line integrity during reverk. As shcvn en Enclosure (A), a minimum of two 2h" main steam line velds vould have to be cut to permit with-drawal of the cooler. These velds have recently been proven acceptable both by non-destructive testing technicues and by satisfactory hydrostatic and stesa testing. Furthermore, having established satisfactory velds, the main steam line veld at the penetration is incorporated in the inservice inspection prcgrim and will undergo periodic surveillance testing.

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Mr. A. Gia=busso Page 3 April 5, 197h Corrective Action Having considered the above, Met-Ed has conc 11.ded that the design modification described in alternative 2, i.e., to plug :he penetration pressurizatien system to penetration 112, will be impl'..cented. No si 6 nificant degradation in reactor building integrity or cooler performance, as a result of this modification is anticipated. The penetration vill retain the capability for future testing, and the testing frequency will be consistent with that of conventional non-pressurized penetrations as described in the Tech Specs. Very truly yours,

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