ML102430204

Post-Accident Monitoring Report

ML102430204
Person / Time
Site:	Calvert Cliffs
Issue date:	08/27/2010
From:	Trepanier T Constellation Energy Group, EDF Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML102430204 (4)

Text

Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 CENG a joint venture of Af Constellation 64,eDF

%0 Energy ' D CALVERT CLIFFS NUCLEAR POWER PLANT August 27, 2010 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit No. 1; Docket No. 50-317 Post-Accident Monitoring Report The attached report is submitted in accordance with Calvert Cliffs Nuclear Power Plant Technical Specification 3.3.10.B. The report is required due to the Unit I Containment High Range Area Monitor having less than required minimum number of operable channels.

Should you have questions regarding this matter, please contact Mr. Douglas E. Lauver at (410) 495-5219.

Thomas E. Trepanier Plant General Manager TET/RDW/bjd

Attachment:

(1) Unit I Post-Accident Monitoring Report cc: D. V. Pickett, NRC Resident Inspector, NRC M. L. Dapas, NRC S. Gray, DNR

ATTACHMENT (1)

UNIT 1 POST-ACCIDENT MONITORING REPORT Calvert Cliffs Nuclear Power Plant, LLC August 27, 2010

ATTACHMENT (1)

UNIT 1 POST-ACCIDENT MONITORING REPORT Calvert Cliffs Nuclear Power Plant, LLC (CCNPP) submits this Post-Accident Monitoring Report concerning an inoperable Unit I containment high range area radiation monitor. This report is required by Technical Specification 3.3.10, Required Action B. 1.

ACTIONS TAKEN During the 2010 refueling outage, the detector 1-RE-5317B failed it calibration check using transfer sources. The detector was replaced and the replacement detector successfully passed the calibration check.

On July 15, 2010 at approximately 1640 hours0.019 days <br />0.456 hours <br />0.00271 weeks <br />6.2402e-4 months <br />, the overhead annunciator associated with the containment high range area monitors actuated. The operators found that the power lamp on 1-RI-5317B was out and the indication was off scale low. The power lamp was depressed in order to check the status of the light bulbs. When the power lamp was depressed, the lamp illuminated and the meter reading returned to its expected level. -,

The channel 1-RI-5317B was declared inoperable and CCNPP entered Technical Specification 3.3.10.,A until a cause of the loss of indication could be determined.

Initial troubleshooting found that the 24 VDC power supply, internal to 1-RI-5317B had high AC ripple.

The vendor specification states that the maximum acceptable AC ripple for this power supply is 50 mVAC. Approximately 200 mVAC ripple was measured on the output. Repairs were begun to replace the power supply.

On approximately August 3, 2010, the 24 VDC power supply was replaced. The output from the replacement power supply was checked and found to be well within vendor specifications.

Post-maintenance testing was completed and channel performance was observed for approximately 2 days.

On August 6, 2010 at approximately 0300,. the control room annunciator associated with 1-RI-5317B again actuated. The operators found the same conditions that were initially reported on July 15, 2010.

Additional troubleshooting was performed. A time domain reflectometer (TDR) was used to determine if there was any degradation in the high voltage and signal coax cables that run from the rate meter in the Control Room to the detectors in Containment.

The TDR detected possible degraded connections in a junction box located in the Auxiliary Building.

During evaluation of the results of the TDR, Condition A in Technical Specification 3.3.10 had expired and CCNPP entered Technical Specification 3.3.10.B, which requires submission of this report in accordance with Technical Specification 5.6.7.

Repair efforts on the connections within the junction box were begun on August 16. The repairs were completed on August 18.

The performance of the channel was observed for approximately one week before any recommendations, concerning returning the channel to service, were made. The analog output from the rate meter to the plant computer was trended and the resulting trend evaluated. On August 25, Engineering made a recommendation to return the channel to service based on the results of the evaluation. The channel was declared operable on August 26, 2010.

I

ATTACHMENT (1)

UNIT 1 POST-ACCIDENT MONITORING REPORT EFFECT ON OPERATION The containment high range area monitors are designed for post-accident use. The two redundant channels provide the plant operator with containment radiation levels on the 69 ft elevation of Containment.

The A channel, !-RI-5317A, remains operable. Channel B is now operable. Alternate monitoring methods are not needed.

CAUSES OF INOPERABILITY Based on the results of the repair, the most likely cause of the failure of the channel is degraded connections in the junction box.

PLANS AND SCHEDULES FOR RESTORING THE SYSTEM TO OPERABLE STATUS The system is currently operable.

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