ML071410078

Post-Accident Monitoring Report

ML071410078
Person / Time
Site:	Calvert Cliffs
Issue date:	05/17/2007
From:	Joseph E Pollock Constellation Energy Group, Constellation Generation Group
To:	Document Control Desk, NRC/NRR/ADRO
References
Download: ML071410078 (3)

Text

Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Constellation Generation Group, LLC Lusby, Maryland 20657 0 Constellation Energy May 17, 2007 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit No. 2; Docket No. 50-318 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 2 Reactor Vessel Water Level Monitoring System having less than the required minimum number of operable channels.

Should you have questions regarding this matter, please contact Mr. Jay S. Gaines at (410) 495-5219.

for Joseph E. Pollock Plant General Manager JEP/CAN/bjd

Attachment:

(1) Unit 2 Reactor Vessel Water Level Monitoring System Report cc: D. V. Pickett, NRC Resident Inspector, NRC S. J. Collins, NRC R. I. McLean, DNR AWo

ATTACHMENT (1)

UNIT 2 REACTOR VESSEL WATER LEVEL MONITORING SYSTEM REPORT Calvert Cliffs Nuclear Power Plant, Inc.

May 17, 2007

ATTACHMENT (1)

UNIT 2 REACTOR VESSEL WATER LEVEL MONITORING SYSTEM REPORT Calvert Cliffs Nuclear Power Plant, Inc. (CCNPP) submits this Post-Accident Monitoring Report concerning an inoperable Unit 2 Reactor Vessel Water Level Monitoring System channel. This report is required by Technical Specification 3.3.10, Required Action B.1.

ACTION TAKEN On April 11, 2007 at approximately 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br />, the CCNPP Unit 2 Reactor Vessel Water Level Monitoring System, Channel A experienced the failure of the six of the eight level position sensors. The failure of these sensors resulted in Channel A being declared inoperable. Calvert Cliffs Technical Specification Bases Section B3.3.10, "Post-Accident Monitoring (PAMS) Instrumentation," requires one of the upper three (vessel head region) and three of the lower five (plenum region) sensors for operability of each Reactor Vessel Water Level Monitor Channel. As a result of the subject failures, CCNPP immediately entered Technical Specification 3.3.10, Condition A. When the Completion Time of Condition A expired, CCNPP entered Technical Specification 3.3.10, Condition B, which requires submission of this report in accordance with Technical Specification 5.6.7.

EFFECT ON OPERATION The Reactor Vessel Water Level Monitoring System instrumentation is designated for post-accident monitoring use. It provides the plant operator with information to assess void formation in the reactor vessel head region and the trend of liquid level in the reactor vessel plenum. The Reactor Vessel Water Level Monitoring System consists of two redundant channels. Reactor Vessel Water Level Monitoring Channel B remains operable with all eight of its sensors functioning normally. The removal of Channel A from operable status eliminates a means of redundant indication. However, alternate methods of monitoring for core and Reactor Coolant System voiding, using pressurizer level, Reactor Coolant System subcooling, hot and cold leg temperature, and core exit thermocouple instrumentation, have been initiated as required by plant procedures.

CAUSES OF INOPERABILITY The cause of inoperability is the failure of six sensors (one is located in the upper region and five are located in the lower region of the reactor vessel). The cause of these failures is unknown at this time.

An apparent cause evaluation is in progress to determine the cause of these failures.

PLANS AND SCHEDULES FOR RESTORING THE SYSTEM TO OPERABLE STATUS Calvert Cliffs Nuclear Power Plant will repair or replace as necessary the Channel A Reactor Vessel Water Level cable and associated connectors during the next forced outage of sufficient duration. If these activities do not resolve the problem, the Channel A Reactor Vessel Water Level sensors will be replaced during the scheduled Unit 2 2009 Refueling Outage. Following these maintenance activities, it is expected that the Reactor Vessel Water Level Monitor Channel A will be returned to operable status.

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