ML19210A191

Abnormal Occurrence 50-289/75-37:on 751021,blocked Strainer on Outlet to Boric Acid Mixtank Decreased Flow Rate.Plant Shutdown Followed to Replace Strainer.Improper Design Allowing for One Strainer W/No Bypass Caused Blockage

ML19210A191
Person / Time
Site:	Three Mile Island
Issue date:	10/31/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A192	List: ML19210A191 ML19210A197
References
GQL-1664, NUDOCS 7910240913
Download: ML19210A191 (3)

Text

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NRC MRIBUTION FOR PART 50 DOCK. ' ATERI AL (TEMPOR ARY FORM)

, CONTROL NO:1ZM 2 FILE: INCIDE'.T REPORT FIL_

FROM: Metropolitan Edison Co DATE OF DOC DATE REC'D LTR TWX RPT OTHER Reading, Pa It r Arrald 10-31-75 11-4-75 XX TO: ORIG CC OTHER SENT AEC PDR XX one signea XX DL SENT LOCAL PDR CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO: .

g u 1 50-289 DESCRIPTION: '

ENCLOSURES:

Ltr reporting abnormal occurrence 175-33 on 10-21-75 concerning an inoperable boric ac ta mix tank. . . . . . . - -

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PLANT NAME: Three Mile Island #1 Y "' M I [ */ i FOR ACTION /INFORMATION 11-e-75 ent BUTLER (L) SCHWENCER (L) ZIEMANN (L) REG AN (E)

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.s . . mera m ~ourss METROPOLITAN EDISON COMPANY PCsT OFFICE BOX 542 RE ADING, PENNSYLVANI A 19603 TELEPHONE 215 - 929 3601 October 31, 1975 '

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r- u n. . cf}/I' t .uu0iGI FiLB COPY Director of Nuclear Reactor Regulation O NO(V4 y

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j U. S. Nuclear Regulatory Cct=ission 'C . /

Washington, D.C. 20555 5 ',A x g),*. ' J

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Dear Sir:

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Docket No. 50-289 Operating License No. DFR-50 In acecrdance with the Technical Specifications of cur Three Mile Island Nucle -

Station Unit 1 (TMI-1), we are reporting the following abnormal occurrence.

(1) Repcrt Number: A0 50-289/75-37 (2a) Report Date: October 31, 1975 (2b) Occurrence Date: October 21, 1975 (3) Facility: Three Mile Island Nuclear Station Unit 1 (h) Identificatien of Occurrence:

Title:

Incperable Scric Acid Mix Tank

?/pe: An abnormal occurrence as defined by the Technical Specificaticns, paragraph 1.8b, in that a source of concentrated beric acid solution in additicn te the Berated Water Sterage Tank was not operable, which canstitutes a violation of Technical Specificatien 3.2.2.

(5) Conditions Prior to Occurrence: ,. *

/

Pcver: Core: 81% /

' l/  %

Elec.: 692 INe $

RC Flow: 138 x 10 lb/hr. 6 's g\,n *s *j*h,s'}

. cy RC Pressure: 2155 psig -

%,, '.s *V<

RC Te=p.-

. l* fp \

579 F '

PR~R Level' . 2LC" 1476 194

e. n. .~.n. . . e, . - 655 7

12663

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(6) Descriptien of Occurrence:

Cn October 21, while filling a Reclai=ed Scric Acid Stcrage Tank (R3AST) frc:

the Ecric Acid Mix Tank (3AMT), it was observed that the ficv rate frc: the 3AMI was decreasing. Investigatien showed that the strainer en the cutlet of the 3AMT collected sufficient fines to partially cbstruct the flew of boif e acid. At that ec=ent, the BAMT ms the source of concentrated beric acid solution designated to meet TecL_ leal Specificatien 3.2.2. The 3AMT vas then icclated for strainer replacement.

I=nediately, a normal plant shutdevn was initiatea and the obstructed strainer was recoved and replaced with a new strainer. The operation was ccepleted in approximately seventeen (17) minutes after which pcVer reduction was terminated and the plant restored to the previous pcVer level.

(7) Designatien of Apparent Cause of Occurrence:

The cause of this occurrence has teen determined to be design /trocedure in that only one strainer, with no bypass, is provided on the cutlet of the 3cric Acid Mix Tank. Also, it is considered that the guidelines for the

'eriedic replacement cf the strainer ver e not adequate.

(8) Analysis of Occurrence:

It has been determined that this cccurrence did not consci cute a threat to the health and safety of the public in that the retaining reactivity control systets were available and could have been used to shutdown the reacter by more than the required minimum shutdevn margin of 1% t.K/K.

(9) Corrective Action:

In addition to the i==ediate action described above, long ters corrective actions are as follows:

a. The pricrity of the preposed =cdification of the BAMT cutlet line strainer to a du al strainer arrangenent vill be increased. This change vill permit in-service replacement of the strainer.

b. A weekly strainer surveillance vill be initated in the interin until the dual strainer arrangenent is installed.

(10) Failure Data: :Iot Applicable.

Similar Occurrences: A0 #75-35 Sincerely,

/)  !? l R. C. Arnold Vice President RCA:JMC:tas ec: Office of Inspection i Enforcement, Region 1 File: 2C.l.1 / 7.7.3 5 1 1476 195