ML061640327
| ML061640327 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 06/08/2006 |
| From: | Joseph E Pollock Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML061640327 (3) | |
Text
Calvert Cliffs Nuclear Power Plant Constellation Generation Group, LLC 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 0 Constellation Energy June 8, 2006 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit No. 2; Docket No. 50-318 Reactor Vessel Water Level Monitoring System Special Report The attached special report is submitted in accordance with Calvert Cliffs Nuclear Power Plant Technical Specification 3.3.10. 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. L. S. Larragoite at (410) 495-4922.
Very truly yours, Joseph E. Pollock Plant General Manager JEP/CAN/bdjd
Attachment:
(1)
Unit 2 Reactor Vessel Water Level Monitoring Systeim Special Report cc:
P. D. Milano, NRC S. J. Collins, NRC Resident Inspector, NRC R. I. McLean, DNR I
ATTACHMENT (1)
UNIJT 2 REACTOR VESSEL WATER LEVEL MONITORING SYSTEM SPECIAL REPORT Calvert Cliffs Nuclear Power Plant, Inc.
June 8,2006
ATTACHTMENT (1)
UNITY 2 REACTOR VESSEL WATER LEVEL MONITORING SYSTEM SPECIAL REPORT Calvert Cliffs Nuclear Power Plant, Inc. (CCNPP) submits this Special Report concerning an inoperable Unit 2 Reactor Vessel Water Level Monitoring System channel. This Special Report is required by Technical Specification 3.3. 10, Condition B, Required Action B.l1.
ACTION TAKEN On May 1, 2006 at approximately 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, the CCNPP Unit 2 Reactor Vessel Water Level Monitoring System, Channel B experienced a failure of the 29 inch level position sensor. The failure of the 29 inch level position sensor, coupled with previous failures of the 71 inch and 50 inch position sensors (all three position sensors are located in the lower, reactor vessel plenum region) resulted in Channel B 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.1, 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 A remains operable with all eight of its sensors functioning normally.
The removal of Channel B 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 three of the lower five (plenum region) sensors. The cause of these failures is unknown at this time. A causal analysis 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 replace the Channel B Reactor Vessel Water Level sensors during the scheduled Unit 2 2007 Refueling Outage.
This replacement was scheduled to be accomplished in conjunction with the Reactor Vessel Head replacement project prior to this failure.
Following this maintenance, it is expected that the Reactor Vessel Water Level Monitor Channel B will be returned to operable status.
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