ML19210A215

Abnormal Occurrence 50-289/75-35:on 751010,improper Mix of Boric Acid Crystals Caused Blockage in Mix Tank.Crystals Settling to Bottom of Tank Clogged Line to Reclaimed Boric Acid Storage Tank.Mixture Mod Should Correct Failures

ML19210A215
Person / Time
Site:	Three Mile Island
Issue date:	10/20/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A216	List: ML19210A215 ML19210A221
References
GQL-1628, NUDOCS 7910240931
Download: ML19210A215 (4)

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NRC Dif ., IBUTION FOR PART 50 DOCKET ' .TE R I AL (TEMPORARY FORM) 12291 CONTROL NO:

FILE: II;CIDEITE REPCF 77L:

F ROft:' Metroplitan Edison Co. DATF OF DOC DATE REC'D LTR TWX RPT OTHER Reading, Pa R .C . Arnold 10-2n-75 10 21 79 vvv ORIG CC OTHER SENT AEC PDR xvv TO: '

NRO 1, signed SENT LOCAL PDR vv CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:

xxxx 1 . 50-289 DESCRIPTION: ENCLOSURES:

Ltr reporting abnormal occurrence #75-35 on 10-10-75 concerning obstructed Boric' Acid .

Mix Tana Outlet Line ......

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METROPOLITAN EDISON COMPANY POST OFFICE BOX 542 READING, PENNSYLVANIA 19603 TELEPHONE 215 - 929-2601 October 20, 1975 GQL 1628 ,

Director of Reacter Regulation --

U. S. Nuclear Regulatory Cc= mission ll

'4ashington, D.C. 20555 ,

Dear Sir:

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Docket No. 50-289 Operating License No. DPR-50 In acecrdance with the Technical Specificatiens of cur Three Mile Island Nuclear Station Unit 1 (""4I-1), we are reporting the folleving abncrmal occurrence.

(1) Report Number: A0 50-289/75-35 (2a) Report Date: October 20, 1975 (2b) Occurrence Date: Cctober 10, 1975 (3) Facility: Three Mile Island nuclear Station Unit 1-g (k) Identification of Occurrence:

Title:

Cbstructed Boric Acid Mix Tank Outlet Line Type: An abncr a1 occurrence as defined by the Technical Specifications, paragraph 1.8b, in that the required volt =e of concentrated beric acid solution to be available fcr critical cperatien, in addition to the berated water storage taA (3'iST), was net available, which constituted a violatic;t of Technical Specification 3.2.2.

(5) Conditions Prior to Occurrer.;e:

Pcver: Cere: 100%

Elec.: Skl ?Ge RC Flc : 139 x 10 l'o/hr.

RC Pressure: 2166 psig 1476

' ?40

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RC Te=p. 579 F PRZE Level: 230" PRZR Te=u.: 6560F

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- c (8) Description of Occurrence:

At approximately C600 hours on Cetober 10, 1975, while the Boric Acid Mix Tank (BAMT) ves designated as the tank to meet Technical Specificatien 3.2.2, an attempt to trat.ifer beric acid from the Beric Acid Mix Tank to the "A" Reclaimed 3cric A .id Storage Tank (RSAST) was made in crder to raise the level in the "A' REAST frc= h72.6 cu. ft. to a'aove 550 cu. ft.

Shortly after the attempted transfer began it was noted that there was no decrease in the EAMT level. An i==ediate investigation revealed that the sucticn to the Boric Acid Mix Tank Pump was nearly dry, indicating that the tank's cutlet line was obstructed. Also, it was discovered that the BAMT

=ixer propeller was disconnected frc= the motor shaft.

The line was i==ediately cleared of obstructions and the f1cv path frc=

the Boric Acid Mix Tank to the boric acid mix tank pumps was verified; thus, the tank was restcred to an operable status within ene hour of discovery of the cbstruction. The heat trace en the associated lines was checked, the temperatures were found to be satisfactory, and the mixer was repaired to operable status.

(7) Designatien of Apparent Cause of Occurrence:

The cause of this occurrence has been determined to be material /erecedure in that prcper =ixing in the HUC during the previous addition of 1:ric acid crystals did not occur due to =ixer failure. Addition procedtres did not insure proper mixer action prior to adding boric acid crystals. As a result of the above, undissolved boric acid crystals settled to the botte=

of the BAMT, blocking its outlet line.

(8) Analysis of Occurrence:

It has been determined that this occurrence did not ecnstitute a threat to the health and safety of the public in that:

a. h72.7 cu. ft. of 8700 pp= boron as beric acid solution was available and operable frc= the REAST and

b. the Scrated '4ater Sterage Tank was available and operable. This is sufficient to borate the Reacter Ccolant System to 15 suberitical margin in the cold conditien even at the vorst time in ccre life with a stuck centrol rod. Additionally,

c. the 3cric Acid Mix Tank was restered to an operable status within ene hour.

(9) Corrective Action:

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

a. The mixer vill be =cdified, as recc== ended by the manufacturer to preclude having similar failures of the mixer.

b. The addition procedures shall be reviewed by the plant staff and precedure change initiated as necessary to ensure prcper beric acid additicns to the BAMT. Supplementary instructions and training vill be provided to the auxiliary operaters to instruct them of the hazards of undissolved bcric acid in the BAMT.

1A76 2AI

(10) Failure Data:

Scric Acid Mix Tank Mixer Mcdel VG7C Serial No. 600L69-1A Eastern Industries Div. of Lfa.

Hamden, Ccnnecticut Similar Occurrences: None '

Sincerely,

'I R.'C.Arrhd Vice President RCA:NC:tas cc: Office of Inspection & Enforcement, Region 1 File: 20.1.1 7.7.3.5.1 1476 242