ML19262A182

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Abnormal Occurrence 50-289/75-04:on 750123-24,unplanned Release of Radioactive Gas.Caused by Inadvertent Loss of Reclaimed Boric Acid Tank Loop Seal.Loop Seal Refilled & Valve RC-V3 Backseated Open.Investigation Under Way
ML19262A182
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 02/03/1975
From: Arnold R
METROPOLITAN EDISON CO.
To:
References
NUDOCS 7910260509
Download: ML19262A182 (4)


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METROPOLITAN EDISON COMPANY

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eoTr cr= ice eox 542 R E A DIN G. PEY:S V A'4I4 I M: TELEPHO'!E

  • 5 - 920-2001 February 3,1975 GQL 0717 Director Directorate of licensing ...

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Washington, D. C.

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Dear Sir:

Operating license DP3-50 Decket #50-239 In accordan e .rith the Technical Specifications for c'tr Three Mile Island I;uclear Station, Unit 1, ve re reporting the following abnor al occurrence:

, (1) Report !!urber: A0 SC-239/'*5-CL (2a) Report Date:

(2b) Occurrence Date: Jerue / 23-2L, 1975 (3) Facility: Three Mile ::.' end ;-2 clear Generating Station, Unit 1 (L) Identificaticn of Cccur ence:

Title: Unplanned Fadicactive Pelease, Caused by an Inadvertent Less of the Pe:lai e.' 30r10 Acid Tank icep Seal Type: M abacr:al ecourrence as defined by the Technical Specifica-tiens, paragraph 1.c2., in that the Unplanned Radioactive Pelease, Caused by the Inaivertent Loss of the Reclaited 3cric Acid Tank 1:00 Se11, vas in an a .o':nt vhich was of significance with respect tc -= '4 ' s prescribed in the Technical Specifi-caticns, Appenii:c 3, pn. a;;raph 2.3.2.a.

(5) Conditi:ns Pricr to Oc:urrence: rne reacter va: in a hot standby cendition with majer plan: p1rameter: as fclievs:

Pover: Care: 1.1

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AC 75-OL 2

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RC Flow: 133 x 1C5 lb/hr RC Pressure: 2155 psig RC Temp.: 5350F oc x<

PRZR Level: 210 in. D D n D)rorH,o w l' PR2R Tc=p.

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65007 (6) Description of Cecurrence:

The pressurizer spray valve (?C-71) was bachaeated to allev replacement of its li=itorque c; era cr. The preasuri:er spray bicek valve (RC-V3) was, therefore, closed and was to be operated only if required to control reacter coolant syste= pressure. When the bicek valve (RC-V3) vas closed, valve stem leak o f to the vent header in the Reacter Building increased to apprcxi=ately 10 gp=. This increased valve stem leak off caused an overpressure condition in the vent header nitrogen cover gas which blankets the R.C. Drain Tank and "A" Peelal=ed Beric Acid Tank, as well as other tanks within the Waste Disposal System. This overpressure in the reclai=ed Ecric Acid Tank ecver gas caused the water loss fro = the tank overflev lecp seal and the subsequent release of radioactive cover gas to the Auxiliary Euilding Ventilation

. System. The Auxiliary Building 'lentilation Systes subsequently discharged the released radicactive cover gas through the statien vent to the at=csphere.

The "A" Reclai=ed Scric Acid Tank Leop Seal was refilled to ter=i-nate the gas release frc= the vent header, the Limitorque operater was replaced, RC-71 was returned to its ner=al shut cendition,1:d the motor operated pressurizer spray block valve (RC-V3) was back-seated to stop the valve ste= leak off. As a result , the source of the unplanned gas release was tenninated.

(7) It is believed that the appt ent cause of the inadvertent loss of the Reclaimed Ecric Acid Tank Loop Seal, and resultant unplanned radioactive release, =ay be due to inadequate design of the nitregen cover gas syste= and/or related syste=s , in that if the syste=(s) would have had sufficient capacity to handle the valve stem leak-off, the occurrence vould not have ha;pened.

(8) Analysis of Occurrence:

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Analysis of statien vent radiation e';1uent recorder charts and Itcal air sa=ples frc= the statien vent indicate that 60 curies of predominately Ze-133 (865) were rele1 sed with a naximum release rate of 1.26 x 105 y3/sec. The average release rate ocep the.three hour and 37 =inute duratien of the release was 1.65 x 10" '!3/sec.

The 2h hcur average concentraticn in the affected area cf the

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an incident re;;rtable ir se::riance vi:5 1C : ~~s.-03 (b) (2),

and additional ir.f:r:151:n vil_ ta f:rva ia' ' - a --"-d anc e vi h 10 CT? 20.L 5 (s). The iver ge :0 cen:r2tien is based on a

=essured 1200 CFM air fl:v thr ufa --a ' a-as cf the relesse.

Calculated concentrati::s ** '-a -a a=- devnvini unrestricted area, basa-1 cn a dilutien f t:: r of y/Q = 7.6 x lo-5 sec/: 13 are 2.6 x 10-5 uCi/=1 fer the 'G tinute naxi=um sni 3.Lh x 10-7 uC1/21 for the three hour and 37 minute durttien of the release.

No statien personnel vere in the 1res of the release, th-*efere no exposures cccur ei iu-ing the pesS. times cf the release. +w.

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release were dresse; in protec:;te 21.:ning ini 2.11-eu -a;

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breathing apparatus. Oositetric levices vern by these individus1s indicated only slight exposures (< 15 tres) .

Based on the above discussion, it has been determined that the health and safety of no indiviinal was endangered as a result of this c.ccurrence.

(9) Corrective Action:

As has been described above, irrediate corrective actions consisted of refilling the affected icop seal, restering FC-V1 to its normal shut cendition, and terninsting the scurce of the release by back-seating EC-V3 open.

The Plant Operations ?eview Cctrittee met shortly af ter the cecurrence, approved the inmediate corrective actions, and a a 1cng tern pre-ventative action recc neniei to the Statien Superintendent that an evaluati:n be conducted of the nitrogen cover gas cystem, and related systems, te deter:ine if there is a design inadequaey, and/cr cpera-ticnal procedural insdequacy, that could have caused this occurrence, and if so, what ein be done to prevent it frc happening again.

D Station Superintendent concurred with PCRC's findings , a censultant has been contracted, and the investigation is in pregress.

(10) Failure Data:

Nct applicable.

Sincerely, 9gned-R. C. ARNOLD R. C. Arnold .

' lice President RCA:DMG:eg

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cc: Directorate cf Fer.Citt./ O aratic.s, egien '

'aclear ?erf at:r-  : nis:i:r 6 n ? ark .w er.ue King cf Frussis, Pennsfirinis I?.06 747.e 20 .1.1,/*I

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{jQ U pO.adm.:i l e bec: !ir. G. A. Olsen, Secre:L/ 3. E. 3odden*

Price Movers Cc==ittee J. J. Colit:

- Edison Electric Institute T. M. Cri== ins 90 Park Avenue 1 s. nelicate - 3es Iev York,::Y 10016 D. ::. Grac#

J. G. Herbein R. L'. Eevard (2)

?. !*. Klingersn

1. L. La.r/er J. P. C'Hani:n - Chairman, PCEO C:'I 1 J. F. Peters J. R. Thorpe - Chairman, GCR3 D'I 1

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