TMI-12-033, Special Report - Accident Monitoring Instrumentation Inoperability

Special Report - Accident Monitoring Instrumentation Inoperability

ML12081A121
Person / Time
Site:	Three Mile Island
Issue date:	03/20/2012
From:	Libra R Exelon Nuclear, Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TMI-12-033
Download: ML12081A121 (2)

Text

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Nuclear TS 3.5.5.2 March 20, 2012 TM1-12-033 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289

Subject:

Special Report - Accident Monitoring Instrumentation Inoperability This Special Report is being submitted pursuant to the requirements of Three Mile Island Nuclear Generating Station, Unit 1, Technical Specification 3.5.5.2, and, Table 3.5-4, Action A. Action A states the following:

ACTION A - With the number of OPERABLE channels less than required by the Minimum Channels OPERABLE requirements:

1. either restore the inoperable channel(s) to OPERABLE status within 7 days of the event, or

2. prepare and submit a Special Report within 30 days following the event outlining the action taken, the cause of the inoperability and the plans and schedule for restoring the system to OPERABLE status.

On 2/19/12, the Reactor Building Purge Exhaust Radiation Monitor RM-G-24 alarmed on the main control room alarm panel which operators investigated and found RM-G-24 rate meter to display an error code of "E0007". Operators followed the alarm response procedure and were able to successfully reset the RM-G-24 rate meter and determined that it was reading accurately. An issue report (IR 01328991) was generated and, during that time, it was noticed that receipt of this alarm (and error code) was the second occurrence in the past two weeks.

On 2/23/12, RM-G-24 alarmed and displayed the error code of "E0007". Operations followed the alarm response procedure and were able to again reset the meter and receive a valid signal. Two minutes later, RM-G-24 alarmed again with the same error code "E0007", at which time the meter was left in the failed state. An issue report was generated (IR 01330995) and the channel declared inoperable and entered (started)

Technical Specification 3.5.5.2, Table 3.5-4 Action A, 7 day and 30 day time clock.

On 2/25/12, TMI Instrument Maintenance (I&C) investigated the failure under Work order M2297889. The investigation revealed the most likely fault was the Detector or Pre-

TMI-12-033 Special Report -

Accident Monitoring Instrumentation Inoperability amp. These are a matched set and sealed by the vendor. Attempts to find a spare Detector or Pre-amp were unsuccessful due to the unique configuration of this detector.

On 2/27/12, the Detector and Pre-Amp were removed and shipped to the vendor for evaluation. An alternate instrument to use in lieu of RM-G-24 was communicated to the Emergency Response Organization.

Calibration of the Detector and Pre-Amp was successfully performed by the vendor however the vendor was unable to duplicate the failure on RM-G-24. The Detector and Pre-Amp have been returned to TMI.

On 3/16/12, continued troubleshooting identified the cause of the error codes to be the RM-G-24 Rate Meter. The Rate Meter was replaced and the Detector and Pre-Amp were connected.

On 3/17/12, calibration of the entire circuit was performed satisfactorily. RM-G-24 has been returned to operable status.

There are no regulatory commitments contained in this letter.

If you have any questions, please contact Dave Atherholt at (717) 948-8364.

Respectfully, R. W. Libra Site Vice President, Three Mile Island Unit 1 Exelon Generation Co., LLC cc: USNRC, Regional Administrator, Region I USNRC, Senior Resident Inspector, TMI Unit 1