RS-09-162, Dresden, Unit 2 - Supplemental Information, Request for Approval of Pipe Flaw Evaluation: Difference between revisions

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{{Adams
#REDIRECT [[RS-09-162, Supplemental Information, Request for Approval of Pipe Flaw Evaluation]]
| number = ML093290088
| issue date = 11/24/2009
| title = Dresden, Unit 2 - Supplemental Information, Request for Approval of Pipe Flaw Evaluation
| author name = Hansen J
| author affiliation = Exelon Generation Co, LLC, Exelon Nuclear
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000237
| license number = DPR-019
| contact person =
| case reference number = RS-09-162
| document type = Letter type:RS
| page count = 4
}}
 
=Text=
{{#Wiki_filter:Exelon Generation 4300 Winfield Road Warrenville, IL 60555 November 24,2009 www.exeloncorp.com Nuclear 10 CFR 50.55a U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 2 Facility Operating License No.DPR-19 NRC Docket No.50-237
 
==Subject:==
Supplemental Information
-Request for Approval of Pipe Flaw Evaluation
 
==Reference:==
 
Letter from J.L.Hansen (Exelon Generation Company, LLC)to U.S.NRC, II Request for Approval of Pipe Flaw Evaluation,1I dated November 16, 2009 In the referenced letter, Exelon Generation Company, LLC (EGC)requested NRC approval of a pipe flaw evaluation for a weld (PD1 A-D14)in the Reactor Recirculation (RR)system piping at Dresden Nuclear Power Station (DNPS), Unit 2 that EGC proposes to leave as-is, without repair.The flaw does not meet the acceptance standards of the American Society of Mechanical Engineers (ASME)Boiler and Pressure Vessel Code (Code)Section XI,"Rules for Inservice Inspection of Nuclear Power Plant Components," 1995 Edition with 1996 Addenda, for continued operation without evaluation.
This letter provides supplemental information concerning this request in response to a Request for Additional Information (RAI)that was communicated by the NRC on November 23,2009, and clarified during teleconferences between EGC and the NRC on November 23 and 24, 2009.The supplemental information is provided in the attachment to this letter.There is no proprietary information contained in either this letter or the referenced letter.EGC requests NRC review and approval of the flaw evaluation provided in the referenced letter by November 25, 2009, in support of unit startup from the current DNPS Unit 2 refueling outage.
November 24, 2009 U.S.Nuclear Regulatory Commission Page 2 Should you have questions concerning this submittal, please contact Mr.Timothy Byam at (630)657-2804.Respectfully, Jeff sen Manager-Licensing
 
==Attachment:==
 
Dresden Nuclear Power Station Unit 2, Recirculation Line Flaw Evaluation, Response to NRC Request for Additional Information cc: Regional Administrator
-NRC Region III NRC Senior Resident Inspector-Dresden Nuclear Power Station ATIACHMENT Dresden Power Station Unit 2 Recirculation Line Flaw Evaluation Response to NRC Request for Additional Information On November 23, 2009, the NRC identified a Request for Additional Information (RAI)with regard to the Dresden Nuclear Power Station (DNPS)Unit 2 flaw evaluation that was submitted to the NRC on November 16, 2009.NRC RAI (1)According to the draft safety evaluation dated November 9,2009 (ML092720245), on the Boiling Water Reactor Vessel and Internals Project (BWRVIP)-62 report,"Technical Basis for Inspection Relief of BWR Internal Components with Hydrogen Injection," the crack growth rate of 1.1 x 10-5 in/hr used in your flaw evaluation can only be used for units having effective hydrogen water chemistry (HWC)and/or acceptable noble metal chemical application (NMCA).The criteria accepted by the NRC staff for demonstrating effective HWC or NMCA are given in the staff's draft SE regarding BWRVIP-62 report, however, the specific acceptance criteria have been classified as proprietary by the BWRVIP.Provide information to clearly demonstrate that the reactor coolant system water chemistry program at Dresden, Unit 2 will maintain the unit's water chemistry parameters in accordance with the acceptance criteria given in the BWRVIP-62 report draft SE over the unit's next operating cycle.EGC Response During a teleconference between Exelon Generation Company, LLC (EGC)and the NRC on November 24,2009, the NRC provided additional clarification of the RAI.Specifically, the NRC indicated that the RAI response should focus solely on the Molar Ratio discussion contained in Attachment C of the flaw evaluation, IITransmittal of Design Information 09-045,'Hydrogen Water Chemistry Data'." Molar Ratio The cycle average measured hydrogen to oxygen molar ratio over the last two DNPS Unit 2 cycles was 495:1 for Cycle 20 and 289:1 for Cycle 21 at the measured location.The measured location is a sample, which is representative of the recirculation loop.As calculated by the EPRI Boiling Water Reactor Vessel and Internals Assessment (BWRVIA)Radiolysis Model, hydrogen is injected into the feedwater at a rate necessary to achieve a hydrogen to oxygen molar ratio of3:1 in the Upper Downcomer (DC_UP)which corresponds to a molar ratio of approximately 3.5: 1 in the recirculation pipe (RC_END).The graph below provides the output of a recent DNPS Unit 2 BWRVIA model.ECP Electrochemical Corrosion Potential (ECP)over the last two DNPS Unit 2 cycles ranged from-491 to-476 mV (SHE)with a goal of<-230 mV (SHE).ECP is currently monitored in the Noble Metals Monitoring Skid (NMMS), which is located on a side loop off of the reactor water cleanup system.
ATTACHMENT Dresden Power Station Unit 2 Recirculation Line Flaw Evaluation Response to NRC Request for Additional Information 7.5 6.5 5.5 2.5 0.5 0.05 0.1 02 Feedwater H2 (ppm)0.25 0.3 0.35 Molar Ratio Vs.Feedwater Hydrogen Dresden Nuclear Power Station Unit 2}}

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