ML14206A920
| ML14206A920 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 07/25/2014 |
| From: | Gallagher M P Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML14206A917 | List: |
| References | |
| RS-14-223 | |
| Download: ML14206A920 (16) | |
Text
M ichael P. Gallagher Vice President.
License Renewal Exelon Generation Exelon Nuclear 200 Exelon Way RS-14-223 July 25, 2014 Kennett Square. PA 19348 610 765 5958 Office 610 765 5956 Fax www.exeloncorp.com michaelp.gallagher@exeloncorp.com Withhold from Public Disclosure in accordance with 10 CFR 2.390. Upon removal of Enclosure A , this Letter is uncontrolled. 10 CFR 50 10 CFR 51 10 CFR 54 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, DC 20555-0001
Subject:
References:
Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 Response to NRC Request for Additional Information, Set 31, dated June 30, 2014, related to the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, License Renewal Application
- 1. Letter from Michael P. Gallagher, Exelon Generation Company LLC (Exelon) to NRC Document Control Desk, dated May 29, 2013, "Application for Renewed Operating Licenses." 2. Letter from Lindsay R. Robinson, US NRC to Michael P. Gallagher, Exelon, dated June 30, 2014, "Requests for Additional Information for the Review of the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, License Renewal Application, Set 31 (TAC NOS. MF1879, MF1880, MF1881, and MF1882)" In Reference 1, Exelon Generation Company, LLC (Exelon) submitted the License Renewal Application (LRA) for the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2 (BBS). In Reference 2, the NRC requested additional information to support NRC staff review of the LRA. This letter provides the response to the Reference 2 Request for Additional Information as follows: 1. Within Enclosure A -Response to Request for Additional Information containing Proprietary Information, based on Westinghouse letter LTR-PAFM-14-70, Rev. 0, Attachment 1, "Byron and Braidwood Units 1 and 2 License Renewal: NRC Request for Additional Information Response, (Proprietary)"
July 25, 2014 U.S. Nuclear Regulatory Commission Page 2 2. Within Enclosure B -Response to Request for Additional Information with Proprietary Information redacted, based on Westinghouse letter LTR-PAFM-14-70, Rev. 0, Attachment 2, "Byron and Braidwood Units 1 and 2 License Renewal: NRC Request for Additional Information Response, (Non-Proprietary)" As Item 1 contains information proprietary to Westinghouse Electric Company, LLC, it is supported by an Affidavit signed by Westinghouse, the owner of the information.
The Affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of Section 2.390 of the Commission's regulations.
Enclosure C of this letter provides the Westinghouse Application for Withholding Proprietary Information from Public Disclosure CAW-14-3996, accompanying Affidavit, Proprietary Information Notice, and Copyright Notice. Accordingly, it is respectfully requested that the information which is proprietary to Westinghouse be withheld from public disclosure in accordance with 10 CFR Section 2.390 of the Commission's regulations.
Correspondence with respect to the copyright or proprietary aspects of the item listed above or the supporting Westinghouse Affidavit should reference CAW-14-3996 and should be addressed to James A. Gresham, Manager, Regulatory Compliance, Westinghouse Electric Company, 1000 Westinghouse Drive, Building 3 Suite 310, Cranberry Township, Pennsylvania 16066. There are no new or revised regulatory commitments contained in this letter. If you have any questions, please contact Mr. Al Fulvio, Manager, Exelon License Renewal, at 610-765-5936.
I declare under penalty of perjury that the foregoing is true and correct. Executed on Respectfully, Vice President
-License Renewal Projects Exelon Generation Company, LLC July 25, 2014 U.S. Nuclear Regulatory Commission Page 3 Enclosures
- A: Responses to Requests for Additional Information (Proprietary)
B: Responses to Requests for Additional Information (Non-Proprietary)
C: Application for Withholding Proprietary Information from Public Disclosure cc: Regional Administrator-NRC Region Ill NRC Project Manager (Safety Review), NRR-DLR NRC Project Manager (Environmental Review), NRR-DLR NRC Senior Resident Inspector, Braidwood Station NRC Senior Resident Inspector , Byron Station NRC Project Manager, NRR-DORL-Braidwood and Byron Stations Illinois Emergency Management Agency -Division of Nuclear Safety RS-14-223Enclosure B Page 1 of 13 Enclosure B Byron and Braidwood Stations (BBS), Units 1 and 2 License Renewal Application Response to Request for Additional Information Non-Proprietary Response RAI 4.3.4-3a
Notes:
- 1. The response contained in this Enclosure does not contain proprietary information. Such information has been redacted from this response as evidenced by the blank space within the brackets shown within the response.
- 2. As further explained in the Proprietary Information Notice and Affidavit contained in Enclosure C, the justification for considering certain information proprietary is indicated by means of lower case letters located as a superscript adjacent to the brackets identifying each proprietary item. These lower case letters correspond to Sections (4)(ii)(a) through (4)(ii)(f) of the Affidavit.
RS-14-223Enclosure B Page 2 of 13 RAI 4.3.4-3a Applicability:
Byron Station (Byron) and Braidwood Station (Braidwood), all units
Background:
License renewal application (LRA) Section 4.3.4 states that the Class 1 components were grouped into transient sections, which is defined as a group of sub-components or locations that experience the same transients. The LRA further states that components that reside in the same transient section can easily be compared with each other to determine the most limiting component (or leading location), which is the location with the highest cumulative usage factor (CUF en) value. The differences in stresses experienced by each component in a transient section are generally the result of the material and geometry differences.
In its response to request for additional information (RAI) 4.3.4-3, by letter dated March 28, 2014, the applicant described its environmentally-assisted fatigue (EAF) screening evaluation for the equipment locations that considered different materials within a transient section. The applicant provided details of its evaluation of the reactor vessel outlet nozzle region as an example to support its methodology description. In its response, the applicant stated that the leading location for this transient section was the safe end location, which is stainless steel, because it produced the highest screening CUF en greater than 1.0.
Issue:
The staff noted that within a transient section that contains components of various materials (e.g., low alloy steel, nickel alloy, stainless steel), the applicant did not provide a basis for selecting a leading location based on the highest CUF en value. The staff noted that the CUF en value of different materials may respond differently when the EAF is being refined in the future. In the example of the reactor vessel outlet nozzle region, the applicant did not provide sufficient justification that the stainless steel component would continue to be the leading location for components made from other materials eliminated during this screening process after the CUF en has been refined for the stainless steel component. The applicant did not justify that the refinement of the higher CUF en of one material would ensure the reduction of CUF en values for another material within the same transient section such that the selected leading location would remain appropriate.
Request: 1. Considering that refinements in CUF en values may not always be equal, especially when evaluating different materials, justify, including any assumptions, that a location made from one material can serve as the leading location for other locations with CUF en values greater than 1.0 within a transient section.
- 2. Identify the transient section, component, location, and material in which one material and location bound other materials and locations within a transient section.
- 3. Confirm that this methodology or justification in Request 1 was applied to all instances identified in Request 2. For those instances where the methodology was not used, RS-14-223Enclosure B Page 3 of 13 provide the different, additional bases for the selection of the leading location for a transient section that considered components of different materials and with CUF en values greater than 1.0.
Exelon Response
- 1. The "refinements in CUF en values" referred to in the Request are those that would be incorporated in a detailed evaluation similar to those performed for the qualification of the NUREG/CR-6260 piping components presented in LRA Table 4.3.4-1. These include more detailed transient loading, in some cases more representative of actual plant operating conditions, more detailed finite element analysis models, coupled with stress combinations according to ASME Section III, NB-3200 methods, and application of the modified rate approach to determine integrated F en values. [
] These influences on the screening process for comparison of locations with different materials in the same transient section are discussed below.
There are cases when it is possible to justify that a location made from one material can serve as the leading location for other material locations with CUF en greater than 1.0 within a transient section. Justification must consider that CUF en refinements "may not always be equal," which means that analysis refinement may affect the current licensing basis (CLB)
CUF and final F en values to different degrees for different materials. Therefore, comparison of screening CUF en results for different material locations within a transient section needed to consider a number of principles to determine leading locations, as described below.
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a,c,e RS-14-223Enclosure B Page 4 of 13
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- e. The F en values for different materials have different ranges for PWR conditions. The largest range is for stainless steel (SS) (2.5-15.3); the next largest range is for Ni alloys (1.0-4.5). The values for carbon and low alloy steel (LAS) are based on the threshold values produced by their equations in NUREG/CR-6583, due to the possible simultaneous values of temperature and DO (Dissolved Oxygen) in PWRs.
[ ]
[
] This leads to the following typical bases used for Byron and Braidwood for comparison of screening CUF en for two locations with different materials to determine which is leading:
Basis Number 1
[
]
Basis Number 2
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Basis Number 3
[
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In a case where these bases above cannot be demonstrated in comparing locations with different materials in the same transient section, it may be necessary to retain both as leading locations for further consideration.
a,c,e a,c,e RS-14-223Enclosure B Page 6 of 13
- 2. All of the bounding locations compared for Byron and Braidwood Units 1 and 2 with different materials and CUF en > 1.0 within a transient section are summarized below, along with related screening information:
Reactor Vessel Transient Section: Location Material [ ]
CUFen Outlet nozzle safe end region:
Safe end - Leading Location SS [ ] 1.688
- See response to Request 3 for additional discussion Pressurizer Transient Section:
Location Material [ ]
CUF en Surge nozzle Structural Weld Overlay (SWOL) - Leading Location SS [ ] 14.329
Unit 1 Replacement Steam Generator (RSG) Transient Section: Location Material [ ]
CUF en Primary Head/Tubesheet Juncture - Leading Location LAS [ ] 2.16
- Value reduced with further detailed screening evaluation
[ ]
a,c,e a,c,e a,c,e a,c,e a,c,e a,c,e a,c,e a,c,e a,c,e a,c,e RS-14-223Enclosure B Page 7 of 13 Unit 2 Original Steam Generator (OSG) Transient Section: Location Material [ ]
CUF en Primary Manway (pad/shell) - Drain hole in Channel Head - Leading Location CS [ ] 1.723 Primary Chamber Drain - Leading Location Ni alloy [ ] 2.69 RCP and Class 1 Piping Transient Sections - all locations in scope of the screening evaluation are stainless steel, and therefore this RAI does not apply.
- 3. Justification of the leading location selection in each transient section from locations with screening CUF en > 1.0 and different materials presented in the response to Request 2 is discussed below. Each transient section containing different materials is evaluated using the principles and bases described in the response to Request 1 and from the methodology provided in response to RAI 4.3.4-5 contained in Exelon letter RS-14-226, dated July 15, 2014, to form the basis for the determination of leading locations.
[
]
a,c,e a,c,e a,c,e a , c , e a,c,e RS-14-223Enclosure B Page 8 of 13 Reactor Vessel Transient Section:
[ ] The fatigue resulting from the CLB stress at the RV outlet nozzle to safe end weld region was addressed for all three adjoining materials. A more detailed screening evaluation of
the weld using the Ni alloy NUREG/CR-6909 fatigue curve and maximum screening F en resulted in a CUF en < 1.0. [
] Base d on these screening comparisons, a refined analysis of the stresses in the RV Outlet nozzle to safe end weld region would continue to demonstrate that the RV Outlet nozzle stainless steel safe end is the leading location. The basis for this conclusion is the original screening criteria, as described in the response to RAI 4.3.4-5, Step 3(i), and does not require the bases in response to Request 1.
Pressurizer Transient Section: [
]
Evaluation of SS locations:
[
]
Evaluation of LAS locations:
[
a,c,e a,c,e a,c,e a,c,e RS-14-223Enclosure B Page 9 of 13
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Pressurizer Transient Section Comparisons:
Location [ ] Material CLB CUF [ ] [ ]
Surge nozzle SWOL [ ] SS 0.9336 [ ] [ ]
Summary of evaluations:
[
]
Therefore, the Surge nozzle SWOL SS location can be concluded as the leading location for the pressurizer. This conclusion from the discussion above is consistent with application of basis number 3 in the response to Request 1.
a,c,e a,c,ea,c,e a,c,e a,c,e a , c , e a , c , ea,c,e a,c,e RS-14-223Enclosure B Page 10 of 13 Unit 1 RSG Transient Section:
[
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Evaluation of Ni alloy locations:
[
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Evaluation of LAS locations:
[
]
a,c,e a,c,e a,c,e RS-14-223Enclosure B Page 11 of 13 Evaluation of SS locations:
[
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Therefore, the Primary Head/Tubesheet Juncture remains as the leading location.
Unit 2 OSG Transient Section:
[
]
CS locations:
[
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Ni alloy locations:
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a,c,e a,c,e a,c,e RS-14-223Enclosure B Page 12 of 13
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LAS locations:
[ ]
Comparison of CS, Ni alloy, LAS leading locations:
Unit 2 Original Steam Generator (OSG) Transient Section Comparisons: Location [ ] Material CUF [ ]
CUF en Primary Manway (pad/shell) - Drain hole in Channel Head- Leading Location [ ] CS 0.99 [ ] 1.723 Primary Chamber Drain- Leading Location [ ] Ni alloy 0.594 [ ] 2.69
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Therefore, both the Primary Manway (pad/shell) - Drain hole in Channel Head, and the Primary Chamber Drain locations were retained as leading locations for the Unit 2 OSGs. As presented above, the methodology or justification described RAI 4.3.4-5 and in the response to Request 1 was applied to all instances identified in the response to Request 2, considering components of different materials and with CUF en values greater than 1.0. Also provided are any additional considerations necessary for the selection of the leading location for a transient section.
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