ML041670380

Request for Additional Information, Main Steam Safety Valve Operability Requirements. TAC Nos. MB6537 and MB6538

ML041670380
Person / Time
Site:	Dresden
Issue date:	06/25/2004
From:	Banerjee M NRC/NRR/DLPM/LPD3
To:	Crane C Exelon Generation Co, Exelon Nuclear
Banerjee M, NRR/ADPT, 415-2277
References
TAC MB6537, TAC MB6538
Download: ML041670380 (5)

Text

June 25, 2004 Mr. Christopher M. Crane, President Exelon Nuclear Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 - REQUEST FOR AMENDMENTS - TECHNICAL SPECIFICATION CHANGES RELATED TO MAIN STEAM SAFETY VALVE OPERABILITY REQUIREMENTS (TAC NOS. MB6537 AND MB6538)

Dear Mr. Crane:

By letter dated October 10, 2002, Exelon Generation Company submitted an amendment request that proposed to increase the number of main steam safety relief valves (SRVs) that are required to remain operable at Dresden Units 2 and 3 from eight to nine in order to meet the American Society of Mechanical Engineers (ASME) overpressure vessel integrity requirement.

Without the additional relief capacity, Dresden Unit 3 will exceed the licensing basis reactor dome and ASME overpressure values after reaching a cycle exposure of 13,800 megawatt days per metric ton of uranium. Exelon indicated that it expected to reach this fuel cycle exposure by July 22, 2004, and later revised this date to July 30, 2004.

To support the amendment request, Exelon submitted an ASME overpressure analysis with nine SRVs in service, using an SRV setpoint tolerance of +/-1 percent. However, in the last several years, Exelon submitted several license event reports (LERs) that report actual as-found SRV drifts of higher than +1 percent. In response to a previous request for additional information, Exelon provided the staff with data for 40 SRVs tested over the last four outages of each unit. Five of the 40 test results showed a setpoint drift of more than 1 percent in the upper direction, with the highest value being +2.29 percent. Due to the small overpressure margin available in the ASME overpressure analysis, the staff cannot accept an ASME overpressure analysis based on a tolerance value lower than that which can be supported by the actual valve performance. Therefore, Exelon should provide an ASME overpressure analysis that (1) is based on a higher setpoint tolerance value supported by SRV performance or (2) bounds SRV valve drifts that have been experienced. To ensure that the Dresden units are operated within the licensing basis ASME overpressure limits, and to allow the staff to complete its review by July 30, 2004, the staff requests that Exelon respond to the attached request for additional information no later than July 8, 2004.

The above request for information (RAI) formalizes the discussion we had in a phone call with Exelon on June 9, 2004, following transmittal of a draft copy of the request in an electronic message to Exelon on June 1, 2004. The Nuclear Regulatory Commission also requests that Exelon submit a supplement to the October 10, 2002, amendment request that revises the technical specification (TS) SRV setpoint tolerances from +/-1 percent to values that are consistent with or bound actual valve performance.

C. Crane If the licensee cannot submit a new ASME overpressure analysis, acceptable to the staff, that either (1) is based on a higher setpoint tolerance value supported by SRV performance or (2) bounds SRV valve drifts that have been experienced, by a date that allows sufficient time for the staff to complete its review before the fuel cycle exposure of 13,800 megawatt days per metric ton of uranium is reached, the staff may reject the licensees October 10, 2002 amendment request. In that case, the licensee will be required to operate the plant in a manner that ensures the design basis ASME overpressure analysis requirements can be met with crediting only 8 valves in operation.

If you have any questions, please contact me at (301) 415-2277.

Sincerely,

/RA/

Maitri Banerjee, Project Manager, Section 2 Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-237 and 50-249

Enclosure:

Request for Additional Information cc w/encls: See next page

C. Crane If the licensee cannot submit a new ASME overpressure analysis, acceptable to the staff, that either (1) is based on a higher setpoint tolerance value supported by SRV performance or (2) bounds SRV valve drifts that have been experienced, by a date that allows sufficient time for the staff to complete its review before the fuel cycle exposure of 13,800 megawatt days per metric ton of uranium is reached, the staff may reject the licensees October 10, 2002 amendment request. In that case, the licensee will be required to operate the plant in a manner that ensures the design basis ASME overpressure analysis requirements can be met with crediting only 8 valves in operation.

If you have any questions, please contact me at (301) 415-2277.

Sincerely,

/RA/

Maitri Banerjee, Project Manager, Section 2 Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-237 and 50-249

Enclosure:

Request for Additional Information cc w/encls: See next page DISTRIBUTION:

PUBLIC PDIII-2 R/F AMendiola PCoates MBanerjee OGC ACRS SReynolds, RIII DLPM DPR FAkstulewicz TFord GHammer DTerao ZAbdullahi KKavanaugh MRing, RIII ADAMS Accession Number: ML041670380 OFFICE PM:PDIII-2 LA:PDIII-2 Tech.Ed DSSA:SRXB DE:EMEB SC:PDIII-2 PD:PDIII-2 NAME MBanerjee PCoates PKleene FAkstulewicz DTerao AMendiola WRuland DATE 06/24/ N/A 6/17/04 6/17/04 6/22/04 06/25/04 06/25/04 OFFICIAL RECORD COPY

Dresden Nuclear Power Units 2 and 3 cc:

Site Vice President - Dresden Nuclear Power Station Senior Vice President, Nuclear Services Exelon Generation Company, LLC Exelon Generation Company, LLC 6500 N. Dresden Road 4300 Winfield Road Morris, IL 60450-9765 Warrenville, IL 60555 Dresden Nuclear Power Station Plant Manager Vice President of Operations - Mid-West Exelon Generation Company, LLC Boiling Water Reactors 6500 N. Dresden Road Exelon Generation Company, LLC Morris, IL 60450-9765 4300 Winfield Road Warrenville, IL 60555 Regulatory Assurance Manager - Dresden Exelon Generation Company, LLC Vice President - Licensing and Regulatory 6500 N. Dresden Road Affairs Morris, IL 60450-9765 Exelon Generation Company, LLC 4300 Winfield Road U.S. Nuclear Regulatory Commission Warrenville, IL 60555 Dresden Resident Inspectors Office 6500 N. Dresden Road Director - Licensing and Regulatory Affairs Morris, IL 60450-9766 Exelon Generation Company, LLC 4300 Winfield Road Chairman Warrenville, IL 60555 Grundy County Board Administration Building Associate General Counsel 1320 Union Street Exelon Generation Company, LLC Morris, IL 60450 4300 Winfield Road Warrenville, IL 60555 Regional Administrator U.S. NRC, Region III Manager Licensing - Dresden, 801 Warrenville Road Quad Cities and Clinton Lisle, IL 60532-4351 Exelon Generation Company, LLC 4300 Winfield Road Illinois Emergency Management Warrenville, IL 60555 Agency Division of Disaster Assistance &

Preparedness 110 East Adams Street Springfield, IL 62701-1109 Document Control Desk - Licensing Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

DRESDEN NUCLEAR POWER UNITS 2 AND 3 REQUEST FOR ADDITIONAL INFORMATION MAIN STEAM SAFETY VALVE OPERABILITY REQUIREMENTS In order for the staff to make a decision concerning Exelons October 10, 2002, amendment request, the staff asks that the licensee respond to the following requests:

1. Provide the results of a core- and cycle-specific American Society of Mechanical Engineers (ASME) overpressure analysis at the most limiting exposure, using upper valve drift tolerances that are either consistent with or bound the performance of the safety relief valves at Dresden Units 2 and 3. If Exelon elects to use upper valve tolerances based on valve testing performance, the tolerances must be based on either (1) Nuclear Regulatory Commission-accepted setpoint calculations and uncertainty treatment methods or (2) a 95/95 confidence level evaluation of the valve test data. The analysis must demonstrate that Dresden Units 2 and 3 can meet the technical specification dome pressure criterion of 1345 psig and the ASME overpressure criterion of 1375 psig.

2. State any changes to the key input parameters or assumptions that affect the overpressure response and differ from the current ASME overpressure analysis-of-record that was reported in the October 10, 2002, amendment request.

ENCLOSURE