ML19262A258

Abnormal Occurrence 50-289/74-24:on 741122,out-of-limit Settings for Reactor Coolant Sys Pressure Trip Setpoints Discovered.Caused by Insufficient Procedural Checks & Possible Component Failure.Transmitters Recalibr

ML19262A258
Person / Time
Site:	Three Mile Island
Issue date:	12/02/1974
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-0526, GQL-526, NUDOCS 7910260594
Download: ML19262A258 (4)

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AEC DISTRIBUTION FOR PART 50 DOCKET ?.1ATERI AL (TEMPORARY FORT.1)

- CONTROL NO: 12313 FILE:

F RO '.1: Metropolitan Edison Co. DATE OF DOC D ATE R EC'D LTR TWX RPT OTHER Peading, Pa. 1960't' 12-2-74 12-5-Th X n_c_ s _ ,,, 4 XX ORIG CC OTHER SENT AEC PDR TO: E DL 1 signed SENT LOCAL POR CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO: ,

1 50-289 X'G DESCRIPTION: Ltr reporting Abnor=al occurrence ENCLOSURES:

A0-50-289/74-24on11-22-74 re out or limit -

settings for the Reactor Ccolant System Pressu:e Trip Setpoints........

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• OFFICE 30x 542 RE AOING, PE NNSYLV ANI A :9000 TEtEPHONE 215 - 929-2601

. . . . , .. w GQL 0526 Director Nhf'y D Cy.

Directorate of Licensing U.S . Atomic Energy Commission Washington, D .C . 20545

Dear Sir:

Docket No. 50-289 Operating License DPR-50 In accordance with the Technical Specifications for our Three Mile Island Nuclear Station, thit 1, we are reporting the following abnorma occurrence : " g (1) Report Number: A0 50-289/74-24 g 'b i <

(2a) Report Date : December 2, 1974 L O g , 6' * .g (2b) Occurrence Date: November 22, 1974 Ye,l (3) Facility : Three Mile Island Nuclear Station, Unit 1 k,

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j (4) Identificatica of Occurrence: O -e *

Title:

Out of Limit Settings for the Reactor Coolant System Pressure Trip Setpoints .

Type: An abnormal occurrence as defined by the Technical Specifications, paragraph 1.8a, in that the Out of Limit Settings for the Reactor Coolant System ?ressure Trip Setpoints constituted safety system settings less conservative than the limiting settings established in the Technical Specifications.

(5) Conditions Prior to Occurrence: The reactor was at steady state power, with major plant parameters as follows:

Power : Core: 55" Elec.: 425 MW (Gross) 6 RC Flow: 138 x 10 lbs/hr RC Press . : 2155 psig }4h4 26}

12313

Directorate of Lich., .g '

. RC Temp.* 579 F PRZR Level: 240 in PRZR Temp.: 650 F (6) Description of Occurrence:

On November 22,1974, pressure transmitter calibration and corresponding pressure trip setpoints for the Reactor Coolant System (RCS) were checked because of conflicting Control Room readings between pressure channels.

Reactor Protection System Channel A was bypassed and the associated pressure transmitter was checked by applying test pressures. This check revealed that the pressure transmitter was out of calibration resulting in a low pressure bistable trip setpoint which was less conservative than required by the Technical Specifications (T.S .) . The transmitter was immediately recalibrated using applicable station procedures and Reactor Protection System Channel A was returned to s ervic e .

Each of the remaining pressure transmitters was then checked in sequence by insuring that all channels were in service and then bypassing the applicable Reactor Protection System channel, applying test pressures, calibrating the transmitter (when needed), and returning the channel to service before bypassing the next channel.

Each channel was found to have one out of limit setpoint as illustrated by the following table:

T.S . Table 2.3-1 Measured Low Pressure Measured High Pressure Applicable Trip Setpoint Trip Setpoint Channel Trip Setpoints A, Low Pressure 1800 1787 B, High Pressure 2355 2356 C, Low Pressure 1800 1784 D, Low Pressure 1800 1798 (7) Designation of Apparent Cause of the Occurrence:

The apparent cause of the occurrence was primarilv procedural in that there were not sufficient procedural checks to moaltor potential instrunent drif t of the RCS pressure transmitters . An additional, possibly contributing, factor was component failure in that the drift of the pressure transmitter instruments may have been greater than it should be.

(8) Analysis of the Occurrence:

The out of limit Reactor Coolant System Pressure Trip Setpoint Settings did not constitute a threat to either the health or safety of the public in that the accident analyses which give rise to the need for Reactor Coolant System Pressure Trips require a low pressure trip by 1770 psi, and a high pressure trip by 2385 psi; and these accident analyses based limits were not exceeded.

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1484 262

Directorate of Licens ng .

(9) Corrective Actions As described above , each transmitter was i= mediately recalibrated before returning the associated Reactor Protection System Channel to s ervice .

At a meeting held af ter the condition was reported, the Plant Operations Review Committee (PORC) reviewed and approved the aLave action and recommended to the Station Superintendent that the following long-term actions be taken:

1. Revise applicable surveillance procedures to require that differences in console Reactor Coolant System Pressure indication (which is determined once per shif t) be compared to a maximum allowable difference, and that applicable pressure transmitter calibrations be checked if this maximum is exceeded, and

2. Consider submitting a Technical Specification change request to Table 2.3-1 to permit a 30 psig transmitter calibration drift.

(This would be within the limits as established by the safety analyses .)

The Station Superintendent concurred with these recommendations and appropriate actions have bean taken to ensure completion of the long-term actions .

(10) Failure Data

a. Previous Failures: None

b. Equipment Identification Westinghouse Electric Cc rporation Reactor Coolant System Narrow Range Pressure Transmitter Model 59PH Sincerely ,

A .

R .

Vice President RCA:RSB:sh File: 7.7.3.5.1/20.1.1 cc: Directorate of Regulatory Operations , Region 1 U.S . Atomic Energy Cocsission 631 Park Avenue King of Prussia, PA 19540 1484 263