ML20216G395

Special Rept:On 980320,declared Unit 2 Reactor Vessel Water Level Monitor Channel Inoperable.Caused by Failure of Three Heated Junction Thermocouples in Lower Five Sensors.Will Replace Channel B Reactor Vessel Water Level Probe

ML20216G395
Person / Time
Site:	Calvert Cliffs
Issue date:	04/15/1998
From:	Katz P BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9804200331
Download: ML20216G395 (2)

Text

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PEnn E. Kru flattimore Gas and Electric Company Plant General Manager Calvert Cliffs Nuclear Power Plant Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby. Maryland 20657 410 495-4101 April 15,1998 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 Reactor Vessel Water Level Monitor - Soccial Report The attached special report is submitted in accordance with Calvert Cliffs Unit 2 Technical Specification 3.3.3.6. The report concerns the inoperability of the Unit 2 Reactor Vessel Water Level Monitor Channel 13 for a period in excess of seven days.

Should you have questions regarding this matter, we will be pleased to discuss them with you.

Very truly yours, ,

,n w PEK/RCG/dtm

Attachment:

(1) Unit 2 Reactor Vessel Water level Monitor Special Report cc: R. S. Fleishman, Esquire 11. J. )iiller, NRC J. E. Silberg, Esquire \

ReSic'ent inspector, NRC S. S. Bajwa, NRC R. i. McLean, DNR v A. W. Dromerick, NRC J. H. Walter, PSC @

/

9804200331 980415 PDR ADOCK 05000318 5 PDR

, , , u ,

, ATTACHMENT (I)

UNIT 2 REACTOR VESSEL WATER LEVEL MONITOR SPECIAL REPORT Baltimore, Gas and Electric Company submits this special report concerning the inoperable Unit 2 reactor vessel water level monitor channel, as required by Technical Specification 3.3.3.6, Table 3.3 10, Item 14.

ACTION TAKEN The Unit 2 Reactor Vessel Water Level Monitor Channel B experienced a failure of the 71" heated junction thermocouple (sensor) on March 20,1998, at approximately 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br />. This failure, coupled with previous failures of the 50" and 19" heated junction thermocouples, resulted in the removal from operable status of Channel B, as defined by Technical Specification 3.3.3.6, Table 3.3-10, due to not meeting the required number of operable sensors in the lower five sensors.

EFFECT ON OPERATION Reactor Vessel Water Level Monitor Channel A remains operable. The removal of Channel B from operable status eliminates a means of redundant indication available.

CAUSES OF INOPERABILITY The cause of the inoperability is the failure of three heated junction thermocouples (sensors) in the lower five sensors. Baltimore Gas and Electric Company believes the failure to be attributable to the bending j of the mineral insulated cables during refueling outages, which causes undue stress and eventually results )

in an open thermocouple indication.

)

l PLANS AND SCIIEDULES FOR RESTORING THE SYSTEM TO OPERABLE STATUS Baltimore Gas and Electric Company had already planned to replace the Channel B Reactor Vessel Water Level probe during the scheduled Unit 21999 refueling outage. A new design being implemented will eliminate the need to bend the mineral insulated cables during refueling outages and, thus, eliminate 1 a failure mechanism. Following the replacement of the probe, it is expected the Reactor Vessel Water Level Monitor Channel B will be returned to opernble status. )

l Baltimore Gas and Electric Company plans to replace the reactor vessel water level monitor probes for both units and both channels so that the above mentioned failure mechanism is eliminated as a potential l cause of reactor vessel water level monitor sensor failures. The current schedule is as follows:

l

• Unit 1 Channel B - 1998 refueling outage-  !

• Unit 2 Channel B - 1999 refueling outage; e Unit 1 Channel A - 2000 refueling outage; and  ;

e Unit 2 Channel A - 2001 refueling outage. l