05000287/LER-1981-006, Forwards LER 81-006/03X-1.Detailed Event Analysis Encl

Forwards LER 81-006/03X-1.Detailed Event Analysis Encl

ML20030C100
Person / Time
Site:	Oconee
Issue date:	04/30/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20030C101	List: 05000287/LER-1981-006, Forwards LER 81-006/03X-1.Detailed Event Analysis Encl 05000287/LER-1981-006-03, /03X-1:on 810324,reactor Protection Sys Channel a High Pressure Trip Found Out of Calibr.Caused by Transmitter Drift.Pressure Transmitter Recalibr
References
NUDOCS 8108250396
Download: ML20030C100 (3)

LER-1981-006, Forwards LER 81-006/03X-1.Detailed Event Analysis Encl

Event date:
Report date:
2871981006R00 - NRC Website

text

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4 Re: Oconee Nuclear Station L

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Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-287/81-06, Revision 1.

The cover letter of the original submittal of this report, dated April 23, 1981, in-correctly iden*:1fied the report as R0-269/81-06. The report number was correct elsewhere in the report.

This report is submitted pursuant to Oconee Nuclear Station Technical Specification 6.6.2.1.b(1), which concerns a Reactor Protec-tive System instrument setting which was less conservative than permitted, and describes an incident which is considered to be of no significance with respect to its effect on the health and sr.fety of the public. The corrective action section has been modified.

V truly yours j

...: to.

k liiam O. Parker, Jr JLJ:pw Attachment cc:

Director Mr. Bill Lavallee Office of Management & Program Analysis Nuclear Safety Analysis Center

~U.S. Nuclear Regulatory Commission Post Office Box 10412 l

Washington, D. C.

20555 Palo Alto, California 94303 i

P!OG250396 810430 M

'8DR ADOCK 05000287 Ig 8f PDR n

DUKE POWER COMPANY OCONEE UNIT 3 Report Number: R0-287/81-06, Revision 1 Report Date: April 30, 1981 Occurrence Date: March 24, 1981 Facility:

Oconee Unit 3, Seneca, South Carolina Identification of Occurrenca:

RPS Channel A RCS High Pressure Trip String Out of Calibration Conditions Prior to Occurrence:

100% FP Description of Occurrence: The Unit 3 RPS Channel A RCS high pressure trip string was found to be out of calibration in the non-conservative direction during the normal refueling outage instrument calibration. This incident was discovered at approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on March 24, 1981. Unit 3 was at 100%

FP after completion of the refueling outage.

Technical Specification 2.3 requires that each RPS channel trip when the RC system pressure is 2300 psig or greater.

The combined pressure transmitter, buffer amplifier, and bistable errors were 0.087 volta DC which result in a 6.96 psig error for the high pressure trip. Therefore, the high pressure trip point for RPS Channel A. would have been 2300.96 psig which exceeds the Techni-cal Specification limit by 0.96 psig.

Apparent Cause of Occurrence: The primary cause of the 0.087 volts DC error was the pressure transmitter, which is a Rosemount Modeln1152GP9A92T0010PB m

transmitter.

The transmitter had drifted low from the last time it was checked,

on May 7, 1980. These transmitters are normally calibrated after refueling ottages when the reactor building temperature is high due to normal operation.

This minimizes calibration shifts when ambient temperatures vary from shut-down to power operation.

Analysis of Occurrence:

The calibration error would have caused channel A to -

trip on high pressure slightly above the Technical Specification requirement and well below the PORV setpoint of 2450 psig and the core protection safety limit of 2750 psig.

The Technical Specification limiting condition instrument setting includes an assumed instrument error for conservatism.

In addition Oconee Nuclear Station RPS setpoints are further reduced to prevent exceeding the Technical Specification limits.

Channels B, C, and D were operable and if any two of them had tripped, then the reactor would have tripped. The public health and safety were in no way endangered by this incident.

l m

. Corrective Action: The pressure transmitter was recalibrated and brought into tolerance when it was found out of calibration.

Follow-up corrective action 5;.11 be to perform an evaluation to see if an increase in the difference between the RTS high pressure trip setpoint and the Technical Specification required trip point is acceptable.

It is anti-cipated that this review will be completed by June 15, 1981.

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