ML090490753
| ML090490753 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/18/2009 |
| From: | Pickett D Plant Licensing Branch 1 |
| To: | Furio P, Simpson A Constellation Energy Group |
| Pickett , NRR/DLPM, 415-1364 | |
| References | |
| TAC MD9774 | |
| Download: ML090490753 (4) | |
Text
From: Douglas Pickett Sent: Wednesday, February 18, 2009 3:56 PM To: 'Furio, Patricia S'; 'Simpson, Art L' Cc: Matthew Mitchell; Mark Kowal; Patrick Purtscher; Glenn Dentel; Neil Perry; Silas Kennedy
Subject:
Calvert Cliffs Verbal Authorization for ISI-020 and ISI-021 Ms. Furio:
Mr. Simpson:
Earlier today, the Nuclear Regulatory Commission provided verbal authorization for Relief Requests ISI-020 and ISI-021 for Calvert Cliffs Nuclear Power Plant, Unit No. 2, as requested in your letter of October 1, 2008. Our letter transmitting the written safety evaluation will be issued in the near future.
Authorizing the approval was Matthew Mitchell, Chief, Vessels & Internals Integrity Branch (CVIB), NRR, and Mark Kowal, Chief, Plant Licensing Branch I-1, NRR. Also on the call were Patrick Purtscher of CVIB and myself.
As part of documenting the verbal authorization, I am including, for your information, the script that Mr. Mitchell read. Please let me know if you have any questions.
I will make this email publicly available in ADAMS.
Douglas V. Pickett, Senior Project Manager Calvert Cliffs Nuclear Power Plant, R.E. Ginna Nuclear Power Plant U.S. Nuclear Regulatory Commission 301-415-1364 Email: douglas.pickett@nrc.gov By letter dated October 1, 2008, as supplemented by letters dated December 18, 2008 and January 23, 2009, Constellation Energy requested NRC approval to use two related alternatives (ISI-020 and ISI-021) to certain requirements of the 1998 Edition of Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the Calvert Cliffs Nuclear Power Plant, Unit 2. The first alternative was requested under the provisions of Title 10 of the Code of Federal Regulations (CFR) 50.55a(a)(3)(i); the second is under 10 CFR 50.55a(a)(3)(ii). The first alternative, ISI-20, requested approval of an alternative to extend the third inservice inspection (ISI) interval from 10 years to 20 years for the examination of reactor vessel (RV) Category B-A welds and Category B-D nozzle-to-vessel welds and nozzle inner radius sections. The second proposed alternative, ISI-021, would place the visual inspections of Category B-N-2 and B-N-3 Welded Core Support Structures, Removable Core Support Structures and Interior Attachment Welds on the same 20 year interval as the Category B-A and B-D components addressed in ISI-020. These requests would extend the subsequent ISI intervals to 20 years so that the third interval inspections would be done prior to June 30, 2019, and would not be repeated again before the end of the current CCNPP, Unit 2 operating license on August 14, 2036.
Regarding ISI-20, the NRC approved topical report WCAP-16168-NP, Revision 2, which provides the risk-informed technical basis for the proposed ISI interval extensions. The analyses in the WCAP used probabilistic fracture mechanics analyses and inputs from the work described in the pressurized thermal shock (PTS) risk re-evaluation documented in NRC NUREG-1806 and NUREG-1874. The reports demonstrated the impact of various ISI intervals on RV through-wall-cracking-frequency (TWCF) due to PTS events. From the results of the studies, the PWR Owners Group (PWROG) concluded that the ASME Code,Section XI 10-year inspection interval for Examination Category B-A and B-D components in PWR RVs can be extended to up to 20 years with no significant increase in TWCF. Their conclusion was considered to apply to any operating PWR as long as critical, plant-specific parameters were bounded by values used in the WCAP analyses.
In the NRC safety evaluation (SE) for the WCAP, several additional requirements were laid out for the acceptance of a plant-specific application of the WCAP to support the granting of an alternative to the requirements in Section XI of the ASME Code. The requirements from this SE relevant to Calvert Cliffs, Unit 2 were:
- 1. The ISI interval dates identified in the request for alternative must adhere to the proposed inspection schedules documented in PWROG letter OG-06-356 dated October 31, 2006.
- 2. The requirements for reporting ISI results found in the draft PTS rule, 72 FR 56275, dated October 3, 2007, must be adopted by implementation of a license condition.
- 3. Calculations of T30 for the purpose of demonstrating plant-specific consistency with material property values cited in the WCAP must be carried out via an NRC approved methodology.
The licensee submitted information necessary to show that the Calvert Cliffs, Unit 2 was bounded by the analyses in WCAP-16168. This information included:
- 2. A license condition which will impose on Calvert Cliffs, Unit 2 the requirements for reporting ISI results found in the draft PTS rule, 72 FR 56275.
- 3. Information regarding input parameters for Calvert Cliffs, Unit 2 RV beltline materials (including unirradiated material properties, chemical compositions, neutron fluence levels, relevant RV surveillance data, etc.) necessary for the staff to verify that the material properties of the Calvert Cliffs, Unit 2 RV are consistent with, or bounded by, those used in the WCAP-16168-NP-A, Revision 2 analyses
- 4. Information regarding the construction of the Calvert Cliffs, Unit 2 RV and operation of the Calvert Cliffs, Unit 2 plant which demonstrated the facilitys compliance with assumptions make in the WCAP-16168-NP-A, Revision 2 analyses Regarding the summary of prior inspections of the Calvert Cliffs, Unit 2 RV, one significant, embedded indication was found in the last ISI which would not comply with the requirements in the draft PTS rule regarding allowable flaw distributions. The licensee concluded that the
significance of the indication was minimal and would not be expected to increase the TWCF to an unacceptable level because:
- 1) the indication is in a low fluence, low embrittlement region of the beltline,
- 2) the overall density of flaws was below that used in the WCAP for the pilot plant which was representative of Calvert Cliffs Unit 2, and
- 3) the plate containing the indication was not the limiting beltline material.
The staff verified the information and calculations provided in the licensees submittals. The staff considered the licensees points regarding the relevance of the indication, performed an independent, quantitative evaluation which supported the licensees conclusions, and noted that growth of the indication had not been observed in prior ISI results. Hence, the staff accepts that the indication does not invalidate the assumptions made in the WCAP and that Calvert Cliffs, Unit 2 is bounded by the WCAP.
In summary, the staff found that, in accordance with 10 CFR 50.55a(a)(3)(i), the proposed alternative, ISI-020, would maintain an acceptable level of quality and safety with regard to ensuring the integrity of the subject Calvert Cliffs, Unit 2 RV.
Regarding the second proposed alternative, ISI-021, the visual inspections of Category B-N-2 and B-N-3 Welded Core Support Structures, Removable Core Support Structures and Interior Attachment Welds are required to be done on the same 10-year interval as the inspections for Category B-A and B-D components addressed in ISI-20.
The visual inspections of Category B-N-2 and B-N-3 components can only be done after the fuel and internals are removed from the RV, which is only normally done at the same time as the ISI of Category B-A and B-D welds. Previous inspections of Category B-N-2 and B-N-3 components performed in 1999 found no significant indications of cracking or any other problems. Likewise, the inspection of Category B-N-2 and B-N-3 components at similar, PWR nuclear power plants has not shown any indication of service-induced degradation. Based on this information, and given the staffs approval of ISI-20, the staff concludes that performing the Category B-N-2 and B-N-3 inspections on a 10-year interval as required by Section XI of the ASME Code would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Hence, the alternative proposed, ISI-021, which would permit the licensee to perform the Category B-N-2 and B-N-3 component inspections on a 20-year interval along with the ISI of Category B-A and B-D components, is acceptable.
The NRC has completed its review of the information provided in the licensees submittals for ISI-020 and ISI-021 regarding Calvert Cliffs, Unit 2. The staff has concluded that the information provided by the licensee supports the granting of alternative ISI-20 consistent with the provisions of 10 CFR 50.55a(a)(3)(i) and the granting of alternative ISI-021 consistent with the provisions of 10 CFR 50.55a(a)(3)(ii). Hence, as Chief of the Office of Nuclear Reactor Regulations Vessel and Internals Integrity Branch, I hereby recommend authorization of the licensees implementation of the proposed alternatives in accordance with the information provided in the licensees letter dated October 1, 2008 as supplemented by the licensees letters dated December 18, 2008, and January 23, 2009.
E-mail Properties Mail Envelope Properties ()
Subject:
Calvert Cliffs Verbal Authorization for ISI-020 and ISI-021 Sent Date: 02/18/2009 3:37:36 PM Received Date: 02/18/2009 3:56:00 PM From: Douglas Pickett Created By: Douglas.Pickett@nrc.gov Recipients:
Patricia.Furio@constellation.com ('Furio, Patricia S')
Tracking Status: None Art.L.Simpson@constellation.com ('Simpson, Art L')
Tracking Status: None Matthew.Mitchell@nrc.gov (Matthew Mitchell)
Tracking Status: None Mark.Kowal@nrc.gov (Mark Kowal)
Tracking Status: None Patrick.Purtscher@nrc.gov (Patrick Purtscher)
Tracking Status: None Glenn.Dentel@nrc.gov (Glenn Dentel)
Tracking Status: None Neil.Perry@nrc.gov (Neil Perry)
Tracking Status: None Silas.Kennedy@nrc.gov (Silas Kennedy)
Tracking Status: None Post Office:
Files Size Date & Time MESSAGE 28339 02/18/2009 Options Expiration Date:
Priority: olImportanceNormal ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: