ML20205C409

Submits Info Related to Scope,Risk Mgt & Summary of Risk for Performing Preventive Maintenance on P-13000-2 Unit Transformer Re License Amend 205

ML20205C409
Person / Time
Site:	Calvert Cliffs
Issue date:	03/26/1999
From:	Miller H BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-MA2334, TAC-MA2335, NUDOCS 9904010188
Download: ML20205C409 (2)

Text

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CHARLES H. CRUSE Baltimore Gas and Electric Company Vice President Calvert Cliffs Nuclear Power Plant Nuclear Energy 1650 Calvert Cliffs Parkway I"sby, Maryland 20657

'10 495-4455 March 26,1999

'U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Additional Information Related to License Amendment No. 205 for Calvert Cliffs Nuclear Power Plant. Unit 2 (TAC No. MA 2334 and MA2335)

REFERENCE:

(a) Telephone Conference, between Mr. J. K. Kirkwood, et al. (BGE) and Mr. A. W. Dromerick, et al. (NRC), March 19, 1999, Clarification of Safety Evaluation Report for Amendment 205 to License No. DPR-69 As requested in Reference (a), the following information related to the scope, risk management, and suumary ofrisk for performing preventive maintenance on the P-13000-2 Unit transformer is provided:

Scope of the Work u Baltimore Gas and Electric Company may elect to perform preventive maintenance on the P-13000-2 Unit transformer and the associated switchgear during the period No. 2A and 28 diesel generators g/

(EDGs)[ sic] are cooled by an alternate cooling configuration. This alternate cooling configuration is described in the Safety Evaluation Report for Unit 2 License Amendment No. 205. In order to establish the boundaries required to safely conduct maintenance on the transformer, the Red Bus, which is in the switchyard, will be de-energized. Both units' 4 kV safety-related buses will be supplied by P-13000-1 during this maintenance. No maintanance will be perforn.ed on 500 kV transmission lines, switchyard equipment, or switchyard components in support of the work on P-13000-2.

Actions to Manage Risk .

The P-13000-2 periodic maintenance will be conducted as an Infrequent Test or Evolution (ITOE) in accordance with applicable plant procedures. Designation as an ITOE is reserved for activities that, due to their integrated plant effect and infrequent performance, have the potential for elevated plant risk if performed improperly. An ITOE involves heightened oversight by plant management, additional actions to ensure the evolution is performed safely, and contingency plans to direct response to unusual occurrences during the maintenance. Precautions are also taken to protect the Black Bus, the remaining in-service unit transformer (P-13000-1), and the integrity of offsite power supplies.

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!* Document Control Desk March 26,1999 l Page 2 I During the periods the Red Bus is de-energized to allow transformer isolation or restoration, Unit I will be subject to the required =tions of Limiting Condition for Operation 3.8.1. l l

Summary of Risk The impact on risk frc< aking P-13000-2 out-of-service with the EDGs in the alternate cooling alignment is acceptable. ine risk for Unit 1 is shown in the following table:

Rhk to Unit 1 l Impact on Unit 1: Without P-13000-2 Outage With P-13000-2 Outage j A. Risk associated with 4.80E-06 4.87E-06 implementing the Safety Evaluation Report and EDG overhauls as planned 4 B. Risk associated with EDG 2.00E-06 2.04 E-06 l overhauls in a typical outage Difference in risk (A. - B.) 2.80E-06 2.83 E-06 Risk to Unit 2 With the EDGs in an alternate cooling alignment and P-13000-2 out-of-service, the risk to Unit 2 will either be extremely low or zero. The risk is zero if the work is performed during the time that Unit 2's core is in the Spent Fuel Pool (SFP)(see SFP Risk). If the work is performed after the Unit 2 core is reloaded and the Refueling Pool is filled, the Unit 2 risk is considered extremely low. Due to j the large volume of water in the Refueling Pool, with the Refueling Pool filled, the time to boiling in the core would be approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />.

SFP Risk With the Unit 2 core in the SFP, the time to boiling will be over 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. With the EDGs in an alternate cooling lineup, the SFP Cooling System is slightly less reliable. However, with a time-tc-boiling of over 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />, the probability of failure to recover is very small. There are multiple options available to cool the SFP or provide makeup water. With the Unit 2 core reloaded in the  !

reactor vessel, the time-to-boil in the SFP will be approximately 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

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

/p .

M CHC/JKK/ dim cc: R. S. Fleishman, Esquire H. J. Miller, NRC

}' J. E. Silberg, Esquire Resident inspector, NRC t

S. S. Bajwa, NRC R.1. McLean, DNR A. W. Dromerick, NRC J. H. Walter, PSC

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