ML19261F201

Abnormal Occurrence 50-289/74-11:on 740613,both Doors of Reactor Bldg Personnel Hatch Opened Simultaneously.Caused by Failure of double-door Interlock Mechanism.Outer Door Closed & Inner Door Operating Mechanism Repaired

ML19261F201
Person / Time
Site:	Three Mile Island
Issue date:	06/21/1974
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-0102, GQL-102, NUDOCS 7910250619
Download: ML19261F201 (4)

Text

AEC D' "1IBUTICN FOR PART 50 ECCKET FX OTAL NOY (TaiPORARY FCFM) CONTROL NO:

FILE: _

FROM: DATE OF DOC DATE REC'D LTR TWX RPT CTHER Metropolitan EdisonCompany Reading, Penn. 19603 Mr. R.C. Arnold 6-21-74 6-24-74 X TO: , ORIG CC OTHER SENT AEC PDR XXX SENT LOCE FOR M AEC 1 signed CLASS UNCLASS PROP INFO INPUT NO CYS REC'D DOCKET NO:

XXX 1 50-289 DESCRIPTION: ENCLOSURES:

Ler reporting an abnnrml occurrence at the Three Mile Island Nuclear Station.... concern. '

... Simultaneous Opening of Both Doors of the Reactor Bldg.. Personnel Hatch.....

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FOR AC'"IC:i/"]CR_ATICN 6-26-74 JB BUTLER (L) / SCHWENCER (L) ZIEMANN (L) REGAN (E)

W/ CYS W/ 7 CYS W/ CYS W/ CYS CLARK (L) STOLZ (L) DICKER (E)

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W/ CYS W/ CYS W/ CYS W/ CYS ICIIEL (L) PURPLE (L) YOUNGBLOOD (E)

W/ CYS W/ CYS W/ CYS W/ CYS m INTERNAL DISTRIBUTION CREG FILE) TECH REVIEW DENTON LIC ASST A/T IND V AEC PDR #HENDRIE GRIMES DIGCS (L) BRAITMAN

1. 0CC SCHBOEDER GAMMILL GEARIN (L) SALTZMAN

/MUNTZING/ STAFF /MACCARY KASTNER /COULBOURNE (L) B. HURT

/ CASE / KNIGHT BALLARD KREUTZER (E)

GIAMBUSSO /PAWLICKI SPANGLER LEE (L) PLANS BOYD /SHA0 MAIGRET (L) MCDONALD

/ MOORE (L)(LWR-2) /STELLO ENVIRO REED (E) CHAPMAN DEYOUNG (L)(LWR-1) VHOUSTON MULLER SERVICE (L) DUBE w/ input SKOVHOLT (L) /NOVAK DICKER SHEPPARD (L) E. COUPE GOLLER (L) wit 0SS KNIGHTON SU_TER (E)

P. COLLINS /IPPOLITO YOUNGBLOOD SMITH (L) /D. THOMPSON (2)

DENISE /IEDESCO REGAN TEETS (L) /KLECKER

,,ALEG OPR /LONG PROJECT MGR WILLIAMS (E) / EISENHUT FILE & REGION (3) /LAINAS WILSON (L)

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EXTERNAL DISTRIBUTION JQ/

1. 1 - LOCAL PDR Harrisburn. Pa.

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/1 - NSIC (SUCHANAN) 1-ASLBP(E/W Bldg, Rm 529) 1-BRCCKHAtIN NAT U S 1 - ASLB 1-W. PENNINGTON, Rm E-201 GT 1-G. ULRIKSON , OR';L 1 - P. R. DAVIS 1-B&M SWINEBRCAD, Rm E-2G1 GT 1-AGMED (RUTH GUSSP&'

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METROPOLITAN EDISON COMPANY SCOT CFFICE 20X 542 RE ADING. PENNSYLV ANI A 19C00 TELEPwCNE 215 - 900-0001 June 21, 197h '~ .'

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Dear Sir:

N e l. .

Operating Licens Ye &-50 Docket No. 50-289 In accordance with the Technical Specifications for the Three Mile Island Nuclear Station, Unit 1, we are reporting the folleving abnormal occur-rence:

(1) Report Number: A0 50-289/Th-11 (2a) Report Date: June 21, 197h (2b) Occurrence Date: June 13,19' 4 (3) Facility: Three Mile Island Nuclear Staticn, Unit 1 (h) Identification of Occurrence:

Title:

Simultaneous Opening of Both Doors of the Reactor Building Personnel Hatch.

?/pe: An abnormal occurrence as defined by Technical Specifica-tions, Paragraph 1.Se, in that both doors of the Reactor Building Persennel Hatch were opened simultaneously at a time when containment integrity was required, which resulted in the abner =al degredation of one of the coundaries designed to contain the radioactive cateria's resulting frc= the fission process.

(5) Ccnditions Prior to Occurrence: Hot shutdevn with caJor plant parameters as fo11cvs: 7

..v,.

Power: Core: 0 Elec: 0

[ g D

RC Flev: 110 X 10 lbs/hr 4}

Directorate of Licensing June 21, 197h RC Pressure: 2155 psis RC Temp.. 520 F PRZR Level: 125 in.

PRZR Te=p.: 650 F (6) Descripticn of Occurrence: At 16h0 cn June 13, 197h, a =aintenance worker, while passing through the reactor building access hatch, inadvertently opened both doors of the Reactor Building Personnel Access Hatch at once.

(7) Designation of Apparent Cause of Occurrence: The simultaneous opening of both Reactor Building Personnel Access Hatch doors was caused by a failure of the double-door intericck. The interlock is designed to prevent both doors frc= being opened at the same time. The interlock did not function due to a failed set screw on the drive shaft of the door opening =echanism.

Also contributing to the occurrence were two other conditions unrelated to the door opening mechanism:

a. The =aintenance worker who operated the doors was unfamiliar with the proper =ethod of door operation;

b. The operating instructions and precautions posted at the door did not provide sufficient guidance for sc=eone inexperienced in operating the door.

(8) Analysis of Occurrence: It is believed that the simultaneous opening of both doors of the Reactor Building Access Hatch did not endanger the health and safety of the public. This belief is based on the folleving significant points of information:

a. The reactor building represents only one of three boundaries designed to contain the radioactive materials resulting frc=

the fission process. The Reactor Building would be required to serve its boundary function cnly in the event that one or

=cre of the other boundaries should fail, which, in the present instance, they did not.

b. The =crentary opening of both Reactor Building doors represented only a temporary breach of a containment boundary; the outer door of the access hatch was i==ediately closed and locked, thus restoring the integrity of the boundary.

(9) Cerrective Action: The i==ediate corrective actions taken censisted of:

a. i==ediately clcsing and Iceking the cuter door of the access ,

hatch, and hb\

Direetcrate of Licensing June 21, 197h 9

b. repairing the operating mechanism for the inner door so that the door could be returned to service.

The F13-t Operations Review Cc =ittee (PCRC) met promptly after the incident and recc = ended to the Station Superintendent that the following lcng-terr. acticns be taken:

a. Post new cperating instructions and precautions at each access;

b. Counsel the maintenance workcr involved in the incident on the procedure for operating the decr.

The Station Superintendent concurred with PORC's recctmendations, and both corrective actions have now been completed.

(10) Failure Eata:

a. Record of Previous Failures:  : Tot Applicable,

b. Equip =ent Identification: '4hile a faulty set screw is con-sidered to have been the primary cause of the present incident, no name plate informaticn is available on that set screw and the name of the set screv manufacturer is unkncvn.

Sincerely, i

-- .\s_, -\

'R. C. Arnold Vice President-Generation RCA:JF7:sh cc: Directorate of Regulatory Cperations, Regica 1 U. S. Atomic Energy Cc==ission 631 Park Avenue King of Prucsia, Pennsylvania 19hC6 File 7.7.3 5 1 20.1.1 kk0