ML19259D462

Environ Incident 50-289/75-08:on 750426,water Discharged to River from Mechanical Draft Cooling Tower Below ETS Temp. Caused by Unusually Cold Weather Conditions Changing Operating Conditions W/O Time to Take Preventive Action

ML19259D462
Person / Time
Site:	Three Mile Island
Issue date:	09/03/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-1469, NUDOCS 7910240685
Download: ML19259D462 (4)

Text

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NRCI-..iTRIBUTION FOR PART 50 DOCK M ATERI AL f (TEMPORARY FORM)

CONTROL NO: 9404

, FILE: Enviro 5-l

( ROM: Metroplitan Edison Co. DATE OF DOC DATE R EC'D LTR TWX I RPT OTHER Reading, Pa R.C. Arnold 4 3-75 75 vvv TO: ORIG CC OTHER SENT NRC POR m Mr. J.P.0'Reilly not- signe<l SENT LOCAL PDR xx CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:

xxx 50-289 DESCRIPTION: ENCLOSURES:

Ltr reporting Environmental Incident Report ~

1. 75-08 on 8-26-75 concerning excessive cooling of Mechanical Draft Cooling Tower , _

( MDCT) dischatge . . . . . . . . -

PLANT NAME:

Three Mile Island #1 FOR ACTION /INFORMATION 9-6-75 JGB BUTLER (L) SCHWENCER (L) ZIEMANN (L) 4 TIC N (E) MIEID(L)

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POST OFFICE BOX 542 READING, PENNSYLVANI A 19603 TELEPHONE 215 - 923-3601 September 3> 1975 -

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Mr. J. P. O'Reilly, Director .-

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office of Inspection and Enforcement, Region l' U. S. Nuclear Regulatory Consission . ,

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Dear Mr. O'Reilly:

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operating License Noi DPR-50 Docket No. 50-289 -'

Three Mile Island Nuclear Station Unit 1 Environmental Incident Report No. 50-289/75-08 In accordance with the Environmental Technical Specifications for Three Mile Island Nuclear Station Unit 1, we are reporting the following Environmental Incident:

(1) Reporting Number: E.I. 50-289/75-08 (2a) Report Date: September 2, 1975 (2b) Incident Date: August 26, 197.t (3) Facility: Three Mile Island Nuclear Generating Station Unit 1 (TMI-1)

(k) Identification of Incident:

Excessive cooling of Mechanical Draft Cooling Tower (MDCT) discharge, which is a violation of the Environmental Technical Specifications, paragrcph 2.1.a (1), and constitutes violation of a Limiting Condition for Operation.

(5) Conditions Prior to Occurrence:

The reactor was at Steady State Power with major plant parameters as follows:

Core: 100%

Elec.: 825 !Ge 1459 125 6

BC Flow: 139 x 10 RC Pressure: 2155 psig Sh0P

-a  % ~

RC Temp: 580 F PRZR Level: 239 in.

PRZR Temp.: 558 F (6) Description of Incident:

On August 26th vater with a temperature of 3.N F below the ambient river temperature (880F at the time) was discharged from the Unit 1 Mechanical Draft Cooling Tower (ICCT). This temperature drop occurred when a cold front moved through the area causing a rapid change in the ECT operating conditions. I==ediate corrective action was taken to regulate the MDCT and the allovable temperature differential was restored within 15 minutes.

(T) Designation of Apparent Cause of Incident:

Unusual environmental condition, io that the cold front roved into the area so quickly (the ambient air temperature dropped from 880F to 76 F in 30 minutes) that the rapid change in MDCT operating conditions which it brought about could not be anticipated. Also, at the time of the incident the ambient river vater temp =rature was greater than 87 F, which established the differential temperature envelope at 0 to -3 F and thereby greatly reduced the time available to the Control Room Operator for taking preventative action.

(8) Analysis of the Incident: -

It is believed that the negative temperature differential reported here did not cause any environmental damage in that the condition lasted only a short time (15 minutes) and was not so severe as to greatly alter the ambient temperature of the river.

(9) Corrective Action:

The only immediate corrective action taken was to restore the temperature differential to within the allevable range by adjusting the MDCT controls.

At a meeting held 4-diately after the incident was reported, the Plant Operation Review Committee (PORC) reviewed and gave its approval of this action. In addition, they recoc= ended to the Station Superintendent that as a long-term action the need to request a change to the Environmental Specifications be evaluated.

(10) Failure Data:

E.I. 's 74-1, Th-8 and 75-7 all involved excessive negative temperature differentials, although in only the first two cases were these excessive tenperature diffemntials related to material failures.

Sincerely, Signed: R.C.ARNCLD Ce l4JI ,

i d,D R. C. Arnold Vice President RCA:JFV:tas

O cc: Director Division of Reactor Licensing U. S. Nuclear Regulatory Co::: mission Washington, D.C. 20555 File: 7.7.3.11.1 20.1.1 1459 127

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