ML14350B366
| ML14350B366 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/15/2014 |
| From: | Thadani M Plant Licensing Branch 1 |
| To: | Craft W Dominion Generation |
| References | |
| TAC MF3078, TAC MF3402 | |
| Download: ML14350B366 (4) | |
Text
1 NRR-PMDAPEm Resource From:
Thadani, Mohan Sent:
Monday, December 15, 2014 2:46 PM To:
Wanda D Craft (Generation - 6) (wanda.d.craft@dom.com); William D Bartron (Generation -
- 4) (william.d.bartron@dom.com)
Cc:
Poehler, Jeffrey; Rosenberg, Stacey
Subject:
RE: REQUEST FOR ADDITIONAL INFORMATION-MILLSTONE 2 AGING MANAGEMENT PROGRAM FOR LICENSE RENEWAL COMMITMENT NUMBER 13.
Wanda and Bill:
By letter dated July 31, 2013, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13218A264), Dominion Nuclear Connecticut, Inc., (the Licensee) submitted information, in support of license renewal commitment number 13, regarding program description for reactor vessel internals (RVI) for Millstone, Unit 2. The submittal contains an updated RVI Aging Management Program and RVI Inspection Plan in accordance with topical report "Material Reliability Program: Pressurized Water Reactor Inspection and Evaluation Guidelines (MRP-227-A).
The NRC staff is reviewing the licensees submittals to determine whether Commitment number13 can be considered fulfilled and will issue a safety evaluation summarizing its conclusions.
By letter dated July 21, 2014, the licensee responded to the NRC staffs May 14, 2014 request for additional information (RAI).
The NRC staff has reviewed the licensees response to the NRCs May 14, 2014 RAI, and has a need for additional information related to some of the licensees responses to the NRCs RAI. The NRC staffs second request for additional information is attached below for the licensees additional responses.
Please provide your responses to the second RAI within 30 days from the date of this email to facilitate timely completion of the NRC staffs review of the licensees request.
- Regards, Mohan C Thadani Senior Project Manager Millstone, Ginna, and Exelon Northeast Fleet Plant Licensing Branch I-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation (301) 415-1476 Mohan.Thadani@nrc.gov REQUEST FOR ADDITIONAL INFORMATION FOR LICENSE RENEWAL COMMITMENT NO. 13 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION, UNIT 2 DOCKET NUMBER 50-336
2 RAI 2-1 For the cast austenitic stainless steel (CASS) core support columns at Millstone Power Station, Unit 2 (MPS2), the licensee was able to screen out thermal embrittlement (TE) for 63 of 68 columns for which certified material test reports (CMTRs) were available. The columns would therefore be susceptible to irradiation embrittlement (IE) and possibly TE for those columns lacking CMTRs. Therefore, in a request for additional information (RAI), the staff requested the licensee to clarify the scope of the core support column weld inspection, and to provide either a functionality analysis for the columns or modify its RVI Inspection Plan to add an inspection of the columns as a Primary or Expansion category if no part of the core support columns other than the welds is covered by the current inspection. The licensee provided the results of its statistical analysis showing those columns for which the ferrite content was not available were extremely unlikely to exceed the TE screening criteria; therefore, the licensee concluded the columns were susceptible to IE only. The licensees July 21, 2014 response to RAI 2 indicates that the licensee considers that the Primary inspection of the core support column welds provides adequate management for IE because a portion of the CASS material is exposed in the weld area to a bounding level of irradiation. However, the licensees response did not discuss actions to be taken if cracking is found in these welds.
Per MRP-191, "Materials Reliability Program: Screening, Categorization, and Ranking of Reactor Internals Components for Westinghouse and Combustion Engineering PWR Design, (Reference 1) and MRP-227-A, the core support column welds and the CASS core support columns are susceptible to the same set of aging mechanisms: cracking due to fatigue, irradiation-assisted stress corrosion cracking (IASCC) and stress corrosion cracking (SCC), and loss of fracture toughness due to TE and IE. Since the weld area includes some of the CASS core support column material, it represents a leading indicator for degradation of the remainder of the core support column. The NRC staff is concerned that since MRP-227-A does not formalize this relationship by classification of the core support columns as an Expansion category component, cracking that could cause loss of function of the columns which have reduced fracture toughness due to IE will not be adequately managed.
What actions would be taken to ensure the integrity of the core support columns if evidence of service-induced cracking exceeding the acceptance criteria of Table 5-2 of MRP-227-A is detected during the Primary inspection of the core support column welds?
RAI 2-2 In RAI 8, Item 1 the staff requested, that the licensee provide the plant-specific fatigue evaluations for the RVI components for which fatigue evaluations are being credited in lieu of inspections.
In its July 21, 2014 response to RAI 8, Item 1, the licensee indicated a plant-specific fatigue evaluation was not performed but that the evaluation for MPS2 was developed based on comparisons and scaling of analyses performed by the vendor for another plant. The response also provided an outline of the methodology of the evaluation.
However, the NRC staff requires more detail of the fatigue evaluation to complete its review. The staff requests the licensee provide the following:
- 1. Provide a reference for the fatigue analysis methodology, such as an ASME Code subsection.
Specifically, was the reference plant methodology per the ASME Code,Section XI, Subsection NG?
- 2. Describe the method by which the effects of the reactor coolant system water environment were considered in the fatigue analysis, or provide a justification for not considering environmental effects.
- 3. Provide the exact CUF calculated for the Core Support Barrel Assembly - Lower Flange Weld and the Lower Support Structure - Core Support Plate, at MPS2.
Reference 1
3 1013234, "Materials Reliability Program: Screening, Categorization, and Ranking of Reactor Internals Components for Westinghouse and Combustion Engineering PWR Design (MRP-191)." July 20, 2009 (ADAMS Accession No. ML091910130)
Hearing Identifier:
NRR_PMDA Email Number:
1763 Mail Envelope Properties (Mohan.Thadani@nrc.gov20141215144600)
Subject:
RE: REQUEST FOR ADDITIONAL INFORMATION-MILLSTONE 2 AGING MANAGEMENT PROGRAM FOR LICENSE RENEWAL COMMITMENT NUMBER 13.
Sent Date:
12/15/2014 2:46:28 PM Received Date:
12/15/2014 2:46:00 PM From:
Thadani, Mohan Created By:
Mohan.Thadani@nrc.gov Recipients:
"Poehler, Jeffrey" <Jeffrey.Poehler@nrc.gov>
Tracking Status: None "Rosenberg, Stacey" <Stacey.Rosenberg@nrc.gov>
Tracking Status: None "Wanda D Craft (Generation - 6) (wanda.d.craft@dom.com)" <wanda.d.craft@dom.com>
Tracking Status: None "William D Bartron (Generation - 4) (william.d.bartron@dom.com)" <william.d.bartron@dom.com>
Tracking Status: None Post Office:
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