ML14175A398
| ML14175A398 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 06/25/2014 |
| From: | Robinson L License Renewal Projects Branch 1 |
| To: | |
| Robinson L | |
| References | |
| TAC MF1879, TAC MF1880, TAC MF1881, TAC MF1882 | |
| Download: ML14175A398 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 June 25, 2014 LICENSEE: Exelon Generation Company, LLC FACILITY: Byron Station, Units 1 and 2 Braidwood Station, Units 1 and 2
SUBJECT:
SUMMARY
OF TELEPHONE CONFERENCE CALL HELD ON JUNE 4, 2014, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND EXELON GENERATION COMPANY, LLC CONCERNING DRAFT REQUEST FOR ADDITIONAL INFORMATION, SET 31, PERTAINING TO THE BYRON STATION AND BRAIDWOOD STATION, LICENSE RENEWAL APPLICATION (TAC NOS. MF1879, MF1880, MF1881, MF1882)
The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of Exelon Generation Company, LLC (Exelon or the applicant), held a telephone conference call on June 4, 2014, to discuss and clarify the staffs draft request for additional information (DRAI),
Set 31, concerning the Byron Station, Units 1 and 2, and the Braidwood Station, Units 1 and 2, license renewal application. The telephone conference call was useful in clarifying the intent of the staffs DRAIs. provides a listing of the participants, and Enclosure 2 contains a listing of the DRAIs discussed with the applicant, including a brief description on the status of the items.
The applicant had an opportunity to comment on this summary.
/RA/
Lindsay Robinson, Project Manager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-454, 50-455, 50-456, and 50-457
Enclosures:
- 1. List of Participants
- 2. List of Draft Request for Additional Information cc w/encls: Listserv
ML14175A398 *concurred via email OFFICE LA:DLR PM:RPB1:DLR BC:RPB1:DLR PM:RPB1:DLR NAME YEdmonds LRobinson YDiazSanabria LRobinson DATE 6/24/14 6/25/14 6/25/14 6/25/14
SUBJECT:
SUMMARY
OF TELEPHONE CONFERENCE CALL HELD ON JUNE 4, 2014, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND EXELON GENERATION COMPANY, LLC CONCERNING DRAFT REQUEST FOR ADDITIONAL INFORMATION, SET 31, PERTAINING TO THE BYRON STATION AND BRAIDWOOD STATION, LICENSE RENEWAL APPLICATION (TAC NOS. MF1879, MF1880, MF1881, MF1882)
DISTRIBUTION EMAIL:
PUBLIC RidsNrrDlr Resource RidsNrrDlrRpb1 Resource RidsNrrDlrRarb Resource RidsNrrDlrRasb Resource RidsOgcMailCenter RidsNrrPMByron Resource RidsNrrPMBraidwood Resource
LRobinson DMcIntyre, OPA EDuncan, RIII JBenjamin, RIII AGarmoe, RIII JMcGhee, RIII JRobbins, RIII VMitlyng, RIII PChandrathil, RIII
TELEPHONE CONFERENCE CALL BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2 LICENSE RENEWAL APPLICATION LIST OF PARTICIPANTS June 4, 2014 PARTICIPANTS AFFILIATIONS Lindsay Robinson U.S. Nuclear Regulatory Commission (NRC)
Mark Yoo NRC On Yee NRC John Hufnagel Exelon Generating Company, LLC (Exelon)
Al Fulvio Exelon Don Warfel Exelon Albert Piha Exelon Tom Quintenz Exelon Don Brindle Exelon Ralph Wolen Exelon Charles Meyer Westinghouse Mark Gray Westinghouse Thomas Meikle Westinghouse ENCLOSURE 1
DRAFT REQUEST FOR ADDITIONAL INFORMATION BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION June 4, 2014 The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of Exelon Generation Company, LLC (Exelon or the applicant), held a telephone conference call on June 4, 2014, to discuss and clarify the following draft request for additional information (DRAI),
Set 31, concerning the Byron Station, Units 1 and 2, and the Braidwood Station, Units 1 and 2, license renewal application (LRA).
DRAI 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 (CUFen) 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 stated that, within a transient section, all locations with materials other than nickel alloy were compared using the same fatigue curves from the American Society of Mechanical Engineers (ASME) Code Section III, Appendix I for each respective material. The applicant further stated that for nickel alloy locations, the effects of the NUREG/CR-6909 fatigue curve were considered when comparing to other locations in a transient section.
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 CUFen greater than 1.0.
Issue:
The staff noted that a comparison of Environmentally Adjusted Cumulative Usage Factor (CUFen) values calculated based on non-ASME and ASME fatigue curves would not be a straight comparison and would require additional consideration and evaluation in order to compare them on an equivalent basis. It is not clear to the staff how the applicant justified that the CUFen values for nickel alloy were compared to the CUFen values for other materials within a transient section on a valid and meaningful basis for Byron and Braidwood, Units 1 and 2.
ENCLOSURE 2
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 CUFen value. The staff noted that the CUFen 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 CUFen has been refined for the stainless steel component. The applicant did not justify that the refinement of the higher CUFen of one material would ensure the reduction of CUFen values for another material within the same transient section such that the selected leading location would remain appropriate.
Request:
Describe and justify that the comparison of CUFen values calculated based on ASME Code Section III, Appendix I, and non-ASME fatigue curves was evaluated and considered on an equivalent basis.
- 1. Considering that refinements in CUFen 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 CUFen 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, provide the different, additional bases for the selection of the leading location for a transient section that considered components of different materials and with CUFen values greater than 1.0.
Discussion: The applicant requested clarification of the request. Following the discussion with the applicant, the staff revised the original draft RAI to focus the issue on the applicants screening process for comparison of environmentally adjusted CUF for components of different materials within a transient section. The staff requested additional information concerning the applicants justification to determine that one material within a transient section can bound other materials in the same transient section. The staff also requested that the applicant provide additional examples, if any, of screening components locations of different materials within a transient section to sufficiently support its methodology and justification. Deleted information is annotated by strikethrough, and additions are annotated by underline. This question will be sent as a formal request titled: RAI 4.3.4-3a.