ML19210A237

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Abnormal Occurrence 50-289/75-19:on 750618,variable Low Reactor Coolant Sys Pressure Trip Setpoints Less Conservative than Tech Specs.Caused by Channel C Trip Setpoint Out of Calibr Due to Instrument Drift
ML19210A237
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 06/27/1975
From: Arnold R
METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A238 List:
References
GQL-1213, NUDOCS 7910240950
Download: ML19210A237 (4)
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Text

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NRCD TRIBUTION FOR PART 50 DOCKE' 'ATERI AL

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,. FILE: INCIDE:7r erm ri'.1 FROM: Mettpolitan "dison Co. DATE OF DOC DATE REC'D I LTh TWX RPT OTHER Reading, Penna. 6-27-75 7-1-75 XXX R.C. Arnold ORib CC OTHER SE 4T AEC POR M Xx TO:

NRC 1 Signed SENT LOCAL PCH CLASS UNCLASS PROPINFO INPUT NO CYS REC'D f.OCKET NO:

XXXX 1 50-289 DESCRIPTION:

ENCLOSURES:

A/O # 75-19, on 6-18-75, concerning Out of Spe :.-

ification Reactor Coolant 1ressure Trip ,

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Three Mile Island #1 PLANT NAME:

FOR ACTION /INFOR.' ATION VCR 7-3-75 BUTLER (L) SCHWENCER (L) ZIEMANN (L) REG AN (E)

W/ Copies W/ Copies W/ Copies W/ Copics CLARK (L) STOLZ (L) DICKER (E) / LE AR (L)

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GI AM BUSSO SHAO SPANG LE R J. LEE (L) FLANS BOYD **p ST E L LO M. M AIG RET (L) MCDONALD ENVIRC S. REED (E) C H AP.i AN MOORE (L) **fHOUSTON DEYOUNG (L) ** ,,NOVAK MULLER M. SERVICE (L) DUBE-(Ltr)

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DENISE J. COLLINS REGAN S KLECKER REG OPR LAIN AS PROJECT LDR / .G. TEETS WILLI AMS(L) (E) EISENHUT REGION (2) BENAROYA V. WILSON (L) *WlGGINTON

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METROPOLITAN EDISON COMPANY --

POST OFRCE BOX 542 R EACING. PENNSYLV ANI A 19603 TELEPHONE 215 - 929-3601 June 27, 1975 GU 1213 ..~

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1 i~ nw-Director Directorate of Reactor Licensing

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'4ashington, DC 20555 V 'A -

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Dear Str:

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Operating License DPR-50 Dceket #50-289 In accordance with Technical Specifications for the Three Mile Island Nuclear Station Unit I, we are reporting t '.e folleving abnormal occurrence.

(1) Report Number: A0 50-289/75-19 (22) Report Date: June 27, 1975 (2b) Occurrence Date: June 18, 1975 (3) Facility: Three Mile Island Nuclear Staticn Unit I (k) Identificaticn of Occurrence: .

Title:

Cut of Specification Reactor Coolant Pressure Trip Setpcint Type: An abnormal occurrence as defined by Technical Specifications, paragraph 1.6a, in that the cut of specification setpoint for the Reactor Protection System (RPS) was less ccnservative than the limiting setting established in the Technical Specifications.

(5) Ccnditions Prior to Occurrence:

Power: Core: 09%

Elect; 850 Eie Gross RC Flcv: lh0.68 x 106 lb/hr RC Pressure: 2155 psig RC Temp: 579cF PRCR level: 2LO inches PR2R terp: 655 0 F (6) Description of Occurrence:} 

                                                                                                                 -[ _A r 13

Cn June 18, 1975, the variable low reactor coolant systen pressure trip setpoints for all four RPS channels were being tested to determine instrument drift as specified in Abnormal Occurrence Report A0 50-289/75-16. Test results shoved that the trip setpoint for one RPS channel was less conservative than required by the Technical Specificaticns. The required and actual trip point for the channel cut of specificaticn was as follows: Table 2.3-1 Trip Setpoint at 590oF Actual Trip Point Channel (16.25T out -7756) Measured at the Sistable C 1831 5 1831.2 The cut-of-specification channel was recalibrated and retested, and the resulting trip setpcint was verified as being within Technical Specification limits. The variable low pressure trip setpcints for the remaining 3 RPS channels were tested and found to be within Technical Specification limits. (7) Designation of Apparent Cause of Occurrence: The apparent cause of the occurrence has been determined to be material, in that the RPS channel C trin setpoint was out of specification because the temperature-to-pressure signal converter was out of calibration due to minor instrument drift. (3) Analysis of Occurrence: It has been determined that the out of specification trip setpcint did not constitute a threat to the health and safety of the public in that:

a. The setpoints for the other 3 RPS channels were within Technical Specification limits and these channels were fully capable of performing their protective functicn, and
b. The setpoint error fcr channel C (0.3 psig level lov) was =cre conservative than the 30 psig reasurement error assumed in the accident safety analysis, so that channel C vas fully capable of per1craing its protective function.

(9) Ccrrective Actions: In addition to the corrective acticns cutlined above the variable icv pressure trip feature fcr all four RPS channels vill be tested each week until the cause of the instrument drift has been determined and ccrrected. 1476 288

The Plant Operations Review Concittee and the Station Superintendent have reviewed and approved the above listed corrective actions and have taken steps to ensure their inplementation. (10) Failure Data:

a. Previcus Failures:

see Abnormal Occurrence reports Ao 50-269/Th-2h, A0 50-269/75-15 

                'And AC 50-269/75-16.
b. Equipment Identification:

Eailey System 880 Reactor Protection System Sincerely, l,' '* R. C./ Arnold Vice President RCA:CWS:1w cc: Office of Inspection and Enforcement, Regica 1 File 7 7.3.5.1 20.1.1 

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