ML070740631

Confirmatory Action Letter, Three Mile Island Nuclear Station, Unit No. 1

ML070740631
Person / Time
Site:	Three Mile Island
Issue date:	03/22/2007
From:	Dyer J Office of Nuclear Reactor Regulation
To:	Crane C AmerGen Energy Co
Miller, G. Edward, 415-2481
References
TAC MD4191, NRR-07-029
Download: ML070740631 (7)

Text

March 22, 2007 CAL No. NRR-07-029Mr. Christopher M. CranePresident and Chief Nuclear Officer Amergen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

CONFIRMATORY ACTION LETTER, THREE MILE ISLAND NUCLEARSTATION, UNIT NO. 1 (TAC NO. MD4191)

Dear Mr. Crane:

This letter confirms commitments by AmerGen Energy Company, LLC (AmerGen), regardingAlloy 82/182 butt welds in the pressurizer at Three Mile Island Nuclear Station, Unit No. 1.

The discovery, in October 2006, of five circumferential indications in three dissimilar metal (DM)welds on the pressurizer at the Wolf Creek Generating Station (Wolf Creek) raised safetyconcerns based on the size and location of the indications. At Wolf Creek, three indicationswere in the pressurizer surge nozzle-to-safe end weld, and two separate indications were in thesafety and relief nozzle-to-safe end welds. These findings also indicated that significantconcerns might exist with the inspection schedules for addressing the pressurizer weldconcerns issued by the industry-sponsored Materials Reliability Program (MRP), in "PrimarySystem Piping Butt Weld Inspection and Evaluation Guideline (MRP-139)."The Nuclear Regulatory Commission (NRC) is concerned about the pressurizer surge nozzle-to-safe end weld indications, as this is the first time that multiple circumferential primarywater stress-corrosion cracking (PWSCC) indications have been identified in a weld. Thiscondition calls into question the degree of safety margin present in past structural integrityevaluations for flawed DM welds susceptible to PWSCC, since multiple stress-corrosioncracking flaws may grow independently and ultimately grow together, significantly reducing thetime from flaw initiation to leakage or rupture. The size of the relief nozzle-to-safe end flaw isalso of concern, as this flaw has a much larger aspect ratio than those assumed in theestimates used to establish the basis for completing the baseline inspections required by theindustry-sponsored MRP. Larger aspect ratios could result in achieving a critical flaw size andrupture before the onset of detectable leakage. The long-term resolution of this issue is expected to involve changes to the American Society ofMechanical Engineers Boiler and Pressure Vessel Code (ASME Code), and will involvechanges to the NRC regulations in Title 10 of the Code of Federal Regulations (10 CFR),Part 50, Section 50.55a, "Codes and standards." The development of the NRC regulations,whether the rule adopts the ASME Code standards or defines separate requirements, will likelybenefit from additional operating experience, continuing assessments, and analysis beingconducted by the NRC and the MRP.

C. Crane Until NRC regulations are revised, it is necessary to establish a minimum set of enhancedreactor coolant system (RCS) DM butt weld inspection expectations for nickel-basedAlloy 82/182 pressurizer surge, spray, safety, and relief nozzle butt welds, including safe endwelds, to supplement existing inspection and other requirements of the ASME Code and NRCregulations. In addition, enhanced monitoring of RCS leakage is needed to promptly identifyany through-wall flaws in the pressurizer surge, spray, safety, or relief nozzle DM butt welds orsafe end DM butt welds to prevent additional degradation from occurring. The above actionsprovide reasonable assurance that there is no undue risk to the health and safety of the publicwhile the NRC regulations are revised. The NRC communicated the need for near-term enhancements to the industry through publicmeetings held on November 30, 2006, December 20, 2006, and February 2, 2007. Licenseessubmitted letters voluntarily committing to the enhanced inspection and leakage monitoringrequirements. After teleconferences with specific licensees held between February 12 throughFebruary 23, 2007, the licensees submitted supplemental commitment letters addressing theNRC staff's concerns regarding inspection, compensatory actions, and reporting.In your letter dated February 21, 2007 (Agencywide Documents Access & Management System(ADAMS) Accession Number ML070520499) you described actions you will take at Three Mile island Nuclear Station, Unit No. 1 for the pressurizer dissimilar metal butt welds containing Alloy 82/182 material. These commitments address: 1) completion schedules for inspection/mitigation of the welds; 2) RCS leak monitoring frequency, action levels, and actions;

3) reporting requirements, and 4) reinspection frequencies. The NRC staff has reviewed these actions and commitments and agrees the actions andcommitments are appropriate to address the potential of PWSCC of the applicable pressurizer dissimilar metal butt welds containing Alloy 82/182 material with clarifications on 6 of the actions/commitments as indicated in bold below regarding inspection schedule, RCS leak monitoring, and reporting.

• AmerGen will complete inspection or mitigation activities on thepressurizer surge, spray, safety, and relief nozzle butt welds and safe end butt welds containing Alloy 82/182 material by December 31, 2007, for Three Mile Island Nuclear Station, Unit No. 1.

• Once the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> evaluation period, i.e. the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period of sustainedincreased leakage, is complete, and the leakrate is still elevated, Three MileIsland Nuclear Station Unit 1 will be placed in Hot Shutdown within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold Shutdown within 36 additional hours and a bare metal visual inspectionof unmitigated Alloy 82/182 pressurizer nozzles will be performed.

• If a post-shutdown inspection identifies the source of the unidentified RCSleakage to originate from a source other than the pressurizer, a pressurizer baremetal visual inspection would not be performed, provided the leak can bequantified and that quantity drops the unidentified RCS leakage below the appropriate threshold(s).

C. Crane *Reports of any Alloy 82/182 pressurizer nozzle connections inspection results forThree Mile Island Nuclear Station Unit 1 will be submitted to the NRC within60 days of the completion date of the inspection. This includes reports of anybare metal visual inspections as a result of increased RCS leak rate, and reports of any corrective or mitigative actions taken on the pressurizer surge, spray, safety, or relief nozzle butt welds and safe end butt welds containing Alloy 82/182 material.*The re-examination of unmitigated welds identified in Attachment 1 of yourFebruary 21, 2007 letter, using ultrasonic techniques, shall be performed withinevery 4 years (as opposed to the MRP-139 requirements of within 5 years)

• The NRC will be informed in writing prior to changing any of thecommitments or actions above or in the referenced letter. These clarifications were discussed with and agreed upon by your staff during a telephonediscussion on March 20, 2007, between Tom Dougherty, Plant Manager, and Michele Evans, Director-Division of Component Integrity, and further clarified through electronic correspondence (ADAMS Accession Number ML070800591).Pursuant to Section 182 of the Atomic Energy Act, 42 U.S.C. 2232, you are required to:1)Notify me immediately if your understanding differs from that set forth above; 2)Notify me if for any reason you cannot complete the actions and commitments within the specified schedule and advise me in writing of your modified schedule in advance of the change; and3)Notify me in writing when you have completed the actions and commitments addressed in this Confirmatory Action Letter.Issuance of this Confirmatory Action Letter does not preclude issuance of an order formalizingthe above commitments or requiring other actions on the part of the licensee; nor does it preclude the NRC from taking enforcement action for violations of NRC requirements that may have prompted the issuance of this letter. In addition, failure to take the actions addressed in this Confirmatory Action Letter may result in enforcement action.In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter andyour response will be made available electronically for public inspection in the NRC PublicDocument Room or from the NRC's ADAMS, accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html. To the extent possible, your response should notinclude any personal privacy, proprietary, or safeguards information so that it can be made available to the Public without redaction. If personal privacy or proprietary information is necessary to provide an acceptable response, then please provide a bracketed copy of your response that identifies the information that should be protected and a redacted copy of your response that deletes such information. If you request withholding of such material, you must specifically identify the portions of your response that you seek to have withheld and provide in detail the bases for your claim of withholding (e.g., explain why the disclosure of information will C. Crane create an unwarranted invasion of personal privacy or provide the information required by 10 CFR 2.390(b) to support a request for withholding confidential commercial or financial information). If safeguards information is necessary to provide an acceptable response, please provide the level of protection described in 10 CFR 73.21.Sincerely,/ra/J. E. Dyer, Director Office of Nuclear Reactor RegulationDocket No. 50-289License No. DPR-50cc: See next page

ML070740631OFFICECPNBDCILPL1-2/PMLPL1-2/LALPL1-2/BCTECH EDDIRS/TANAMETLupoldESullivanVNersesCSolaHChernoffHChangRPascarelliDATE 3 /20 /073/22/07 3 /20/07 3 /20/07 3 /20/07 2/28/073/21/07 OFFICECPNB/BCDRP/D RGN 1DORL/DDCI/DAD:DESNRR/D NAMETchan(GBG for)DLew (per e-mail)CHaney(MCC for)Mevans(WHB for)JGrobeJDyerDATE 3/20/07 3 /21/073/22/073/22/073/22/073/22/07

Three Mile Island Nuclear Station, Unit 1 cc:

Site Vice President - Three Mile Island Nuclear Station, Unit 1 AmerGen Energy Company, LLC P. O. Box 480 Middletown, PA 17057Senior Vice President - Nuclear ServicesAmerGen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555Vice President - Operations, Mid-Atlantic AmerGen Energy Company, LLC 200 Exelon Way, KSA 3-N Kennett Square, PA 19348Vice President - Licensing and Regulatory AffairsAmerGen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555Regional Administrator Region I U.S. Nuclear Regulatory Commission

475 Allendale Road King of Prussia, PA 19406ChairmanBoard of County Commissioners of Dauphin County Dauphin County Courthouse Harrisburg, PA 17120ChairmanBoard of Supervisors of Londonderry Township R.D. #1, Geyers Church Road Middletown, PA 17057Senior Resident Inspector (TMI-1)U.S. Nuclear Regulatory Commission P.O. Box 219 Middletown, PA 17057Director - Licensing and Regulatory AffairsAmerGen Energy Company, LLC 200 Exelon Way, KSA 3-E Kennett Square, PA 19348DirectorBureau of Radiation Protection Pennsylvania Department of Environmental Protection Rachel Carson State Office Building P.O. Box 8469 Harrisburg, PA 17105-8469Plant Manager - Three Mile Island Nuclear Station, Unit 1 AmerGen Energy Company, LLC P. O. Box 480 Middletown, PA 17057Regulatory Assurance Manager - Three Mile Island Nuclear Station, Unit 1 AmerGen Energy Company, LLC P.O. Box 480 Middletown, PA 17057Ronald Bellamy, Region IU.S. Nuclear Regulatory Commission

475 Allendale Road King of Prussia, PA 19406Michael A. SchoppmanFramatome ANP Suite 705 1911 North Ft. Myer Drive Rosslyn, VA 22209Vice President, General Counsel and SecretaryAmerGen Energy Company, LLC 2301 Market Street, S23-1 Philadelphia, PA 19101 Three Mile Island Nuclear Station, Unit 1 cc:

Dr. Judith JohnsrudNational Energy Committee Sierra Club 433 Orlando Avenue State College, PA 16803Eric EpsteinTMI Alert 4100 Hillsdale Road Harrisburg, PA 17112Correspondence Control DeskAmerGen Energy Company, LLC P.O. Box 160 Kennett Square, PA 19348Manager Licensing - Three Mile Island Nuclear Station, Unit 1 Exelon Generation Company, LLC 200 Exelon Way, KSA 3-E Kennett Square, PA 19348Assistant General CounselAmerGen Energy Company, LLC 200 Exelon Way Kennett Square, PA 19348