ML14035A534
| ML14035A534 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 02/20/2014 |
| From: | Robinson L License Renewal Projects Branch 1 |
| To: | |
| Robinson L, 415-4115 | |
| References | |
| TAC MF1879, TAC MF1880, TAC MF1881, TAC MF1882 | |
| Download: ML14035A534 (9) | |
Text
LICENSEE:
FACILITY:
SUBJECT UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 February 20, 2014 Exelon Generation Company, LLC Byron Station, Units 1 and 2 Braidwood Station, Units 1 and 2
SUMMARY
OF TELEPHONE CONFERENCE CALL HELD ON JANUARY 22, 2014, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND EXELON GENERATION COMPANY, LLC CONCERNING DRAFT REQUEST FOR ADDITIONAL INFORMATION PERTAINING TO THE BYRON STATION AND BRAIDWOOD STATION, LICENSE RENEWAL APPLICATION (TAG NOS.
MF1879, MF1880, MF1881, MF1882)
TheUS. Nuclear Regulatory Commission (NRC or the staff) and representatives of Exelon Generation Company, LLC (Exelon or the applicant), held a telephone conference call on January 22, 2014, to discuss and clarify the staff's draft requests for additional information (ORAls), Set 13, 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 staff's ORAls. provides a listing of the participants and Enclosure 2 contains a listing of the ORAls discussed with the applicant, including a brief description on the status of the items.
The applicant had an opportunity to comment on this summary.
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
February 20, 2013 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 JANUARY 22, 2014, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND EXELON GENERATION COMPANY, LLC CONCERNING DRAFT REQUEST FOR ADDITIONAL INFORMATION 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 January 22, 2014, to discuss and clarify the staff's draft requests for additional information (ORAls), Set 13, 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 ORAls. provides a listing of the participants and Enclosure 2 contains a listing of the ORAls discussed with the applicant, including a brief description on the status of the items.
The applicant had an opportunity to comment on this summary.
IRA/
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 Requests for Additional Information cc w/encls: Listserv DISTRIBUTION: See next page ADAMS Acce N
ML14035A534 SSIOn o.:
OFFICE LA:DLR PM: RPB1:DLR NAME YEdmonds LRobinson DATE 2/12/14 2/19/14 PM: RPB 1 :DLR JDaily 2/20/14 OFFICIAL RECORD COPY
- concurred via email BC:RPB1 :DLR PM:RPB1:DLR YDiazSanabria LRobinson 2/20/14 2/20/14
TELEPHONE CONFERENCE CALL BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2 LICENSE RENEWAL APPLICATION PARTICIPANTS Lindsay Robinson John Daily Christopher Hunt Angie Buford John Hufnagel Albert Piha AI Fulvia Don Warfel Jim Annett Gary Becknell Don Brindle Ralph Walen Paul Cervenka Dylan Cimock LIST OF PARTICIPANTS January 22, 2014 AFFILIATIONS U.S. Nuclear Regulatory Commission (NRC)
NRC NRC NRC Exelon Generating Company, LLC (Exelon)
Exelon Ex elan Exelon Exelon Exelon Exelon Exelon Exelon Exelon ENCLOSURE 1
DRAFT REQUEST FOR ADDITIONAL INFORMATION BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION January 22, 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 January 22, 2014, to discuss and clarify the following draft requests for additional information (ORAls) concerning the Byron Station, Units 1 and 2, and the Braidwood Station, Units 1 and 2, license renewal application (LRA).
DRAI B.2.1.31-1 Applicability:
Byron Station (Byron) and Braidwood Station (Braidwood)
Background:
The Generic Aging Lessons Learned {GALL) Report aging management program (AMP) XI.S3 recommends that the ASME Section XI, Subsection IWF AMP augment the requirements of the existing ASME Section XI, Subsection IWF program (required in accordance with 10 CFR 50.55a) to include monitoring of high-strength structural bolting with actual measured yield strength greater than or equal to 150 ksi or 1,034 MPa for cracking. Several program elements of the GALL Report AMP XI.S3 specify recommendations for aging management of high-strength structural bolting:
- 1. The "Preventive Actions" program element of the GALL Report AMP XI.S3 recommends (1) using bolting material that has an actual measured yield strength less than 150 ksi; and (2) for structural bolting consisting of ASTM A325, ASTM F1852, and/or ASTM A490 bolts, the preventive actions for storage, lubricants, and stress corrosion cracking (SCC) potential discussed in Section 2 of Research Council for Structural Connections (RCSC) publication "Specification for Structural Joints Using ASTM A325 or A490 Bolts" need to be used.
- 2. The "Parameters Monitored or Inspected" program element recommends that high-strength structural bolting susceptible to sec be monitored for sec.
- 3. The "Detection of Aging Effects" program element recommends that, for high-strength structural bolting in sizes greater than 1" nominal diameter, volumetric examination should be performed in addition to the VT-3 examination to detect cracking and that this volumetric examination may be waived with adequate plant-specific justification.
During an onsite audit and review of the LRA AMP, "ASME Section XI, Subsection IWF," the staff noted that the AMP states IWF supports at Byron and Braidwood do not use high-strength bolts susceptible to sec. However, in discussions with the applicant during its onsite audit, the staff noted that there may be high-strength bolting (i.e., ASTM A490)
ENCLOSURE 2 in sizes greater than 1" diameter and actual yield strength greater than 150 ksi that is applicable to the IWF program but that was not considered for SCC potential, as recommended in the GALL Report AMP XI.S3. Specifically
- 1. The AMP does not state whether the applicant plans to discontinue use of high*strength structural bolting (actual yield strength greater than 150 ksi).
- 2. If there are structural bolts that are high-strength and greater than 1" diameter, it is not clear if or how the applicant plans to manage cracking due to sec in accordance with the recommendations of the GALL Report AMP XI.S3.
Request
- 1.
Identify whether there are high-strength structural bolts (i.e., ASTM A490) that were not previously identified for aging management of cracking due to SCC in accordance with the GALL Report AMP XI.S3. If ASTM A490 bolts are used but are not considered for sec potential, provide technical justification for this exception to the recommendations of the GALL Report.
- 2. Describe how the recommendations in the "Preventive Actions," "Parameters Monitored or Inspected," and "Detection of Aging Effects" program elements are addressed, including the use of high-strength bolting materials, preventive actions for storage, lubricants, and sec in accordance with Section 2 of the RCSC document and the VT-3 utilized to manage aging for sec potential. If the program will not address the recommendations in the above-mentioned program elements for high-strength bolting or does not manage aging for these components, provide the associated technical justification.
Discussion: The applicant requested clarity on the staffs request. This ORAl will be sent as a formal RAI titled "RAI 8.2.1.31-1."
ORAl 8.2.1.31-2 Applicability:
Byron and Braidwood
Background:
The "Preventive Actions" program element of the GALL Report AMP XI.S3 states that the use of molybdenum disulfide (MoS2) as a lubricant is a potential contributor to SCC, especially when applied to high-strength bolting. The applicant's ASME Section XI, Subsection IWF AMP basis document states that MoS2 was used as a lubricant for faying surfaces of NSSS supports but not as a thread lubricant.
Issue:
There is no enhancement to the program to specifically prohibit the use of MoS2 lubricants on structural bolting. It is not clear to the staff whether the applicant plans to prohibit the use of MoS 2 lubricant for structural bolting in the future.
Request:
State whether the program will be enhanced to specifically prohibit the use of Mo82 on structural bolting. If so, update the LRA and updated final safety analysis report supplement to include this enhancement. If not, state how the program will ensure that MoS2 lubricant is not used or that it will not be a potential contributor to sec.
Discussion: The applicant requested clarity on the staffs request. This ORAl will be sent as a formal RAI titled "RAI 8.2.1.31-2" DRAI 8.2.1.31-3 Applicabilitv:
Byron and Braidwood
Background:
The "Detection of Aging Effects" program element of the GALL Report AMP XI.S3 recommends that for high-strength structural bolting (actual measured yield strength greater than 150 ksi) in sizes greater than 1" diameter, volumetric examination should be performed in addition to VT-3 examination. The GALL Report also states that this volumetric examination may be waived with adequate plant-specific justification.
LRA Section 8.2.1.31 states that for the 5" diameter high-strength reactor coolant pump {RCP) hold-down bolts at Byron and Braidwood and the 1 % diameter pressurizer hold-down bolts at Braidwood, the applicant takes exception to the GALL Report recommendation that periodic volumetric examinations be performed. The staff reviewed LRA Section B.2.1.31 ASME Section XI, Subsection IWF AMP supporting documentation during the onsite audit and noted that the applicant does not consider cracking due to SCC applicable to these bolts. The applicant uses the following plant-specific justification to waive the GALL Report recommended volumetric examinations in addition to VT-3 visual examination:
The bolt design is in a configuration that precludes water from penetrating the interface between the bolt head and support surface and seeping beneath the bolt head, which prevents the potential initiation of corrosion. The bolts were torqued to bear tightly on the support surface.
Metal-plated stud bolting is not used, which could cause degradation due to corrosion or hydrogen embrittlement.
An approved lubricant was applied to the bolts; this lubricant did not contain MoS2.
There have been no recordable indications of degradation identified by ASME Section XI, Subsection IWF program examinations that would indicate the potential for SCC to occur.
The staff reviewed the applicant's plant-specific justification to waive volumetric examinations of the RCP hold-down bolts and pressurizer hold-down bolts as well as the applicant's plan to use visual examinations only to manage aging of these components. The staff identified the following concerns:
The ASME Section XI, Subsection IWF AMP basis documents state that the RCP hold-down bolts are located in an "air with borated water leakage" environment Since there is a potentially moist environment, susceptible material, and stress present to cause sec, the GALL Report AMP XI.S3 recommends that high-strength bolting in sizes greater than 1" should be managed for SCC. An onsite review of the design drawings for the bolt configuration determined that there is no physical seal preventing water intrusion beneath the bolt head. The staff does not have enough information to confirm that the surface between the bolt head and support surface is watertight.
The AMP basis document states that the applicant examines the bolts using ASME Section XI, Subsection IWF Table IWF-2500-1, which states that for supports other than piping supports (class 1, 2, 3 or MC), VT-3 examination of 100 percent of the bolts should be performed each inspection interval of ten years. The staff needs more information on how the VT-3 examination will ensure that SCC will be detected and that any effects of cracking due to SCC will be managed. The AMP does not indicate what parameters or criteria would be used to detect SCC and how they would be effective in identifying sec potential.
The program does not identify actions to be taken (i.e., use ASME lWF criteria for expansion of scope, increase in inspection frequency, or perform volumetric examinations) if there are indications that sec could be occurring.
The applicant's previous experience with the IWF program indicates that cracking due to SCC has not been found to be a degradation mechanism. However, since the IWF examination does not include volumetric examination for cracking beneath the bolt head for high-strength structural bolts greater than 1" diameter, the operating experience referenced by the applicant does not preclude the potential for sec for these components. During the onsite audit, the applicant stated that it does not have a history of volumetric examinations of similar bolting to show that there is no evidence of sec.
Request:
Provide further technical justification to support a plant-specific waiver for periodic volumetric examination of high-strength RCP and pressurizer hold-down bolts. Discuss how the ASME Section XI, Subsection IWF program will verify the absence of cracking due to SCC for the 5" SA540 high-strength RCP hold-down bolts and the 1 %" pressurizer hold-down bolts.
Specifically:
- 1. For both plants, provide results of any plant-specific history of volumetric examination of high-strength bolts in a similar environment to support a plant-specific justification to waive future volumetric examinations as recommended in the GALL Report. If there is no history of volumetric examination of the referenced bolts, state whether any volumetric examinations (or alternative methods) will be conducted prior to period of extended operation (PEO) to confirm that cracking due to sec has not affected the bolt threads.
- 2. State what parameters or criteria will be used to detect SCC or a corrosive environment and how visual inspections will be effective in detecting future SCC or corrosive environment. State how the program will ensure that a noncorrosive environment is maintained throughout the IWF interval.
- 3. State what actions will be taken with respect to augmented examinations if inspections result in indications that there is degradation or a corrosive environment that could lead to sec, including any plans for supplemental volumetric examinations or evaluations.
Discussion: The applicant requested clarity on the staffs request. This ORAl will be sent as a formal RAI titled RAI 6.2.1.31-3."
DRAI 8.2.1.10*1 Applicability:
Byron and Braidwood
Background:
LRA Section 8.2.1.1 0 Enhancement 1 provides three options the applicant may take to disposition potential primary water stress corrosion cracking (PWSCC) of the Byron and Braidwood Units 1 and 2 steam generator divider plate welds to the primary head and tubesheet cladding. The second option for Enhancement 1 indicates that an analytical evaluation will be performed to establish a technical basis to disposition the potential degradation mechanism.
Option 2: Analysis Perform an analytical evaluation of the steam generator divider plate welds in order to establish a technical basis which concludes that the steam generator reactor coolant pressure boundary is adequately maintained with the presence of steam generator divider plate weld cracking. The analytical evaluation will be submitted to the NRC for review and approval prior to entering associated PEO.
In addition, LRA Section B.2.1.1 0 Enhancement 2 provides three options the applicant may take to disposition PWSCC of the Byron and Braidwood Unit 1 steam generators tube-to-tubesheet welds. The second and third options for Enhancement 2 indicate that an analytical evaluation will be performed to determine that the steam generator tube-to-tubesheet welds are not susceptible to PWSCC or that the reactor coolant pressure boundary will be redefined where the steam generator tube-to-tubesheet welds are not required.
Option 2: Analysis-Susceptibility Perform an analytical evaluation of the steam generator tube-to-tubesheet welds to determine that the welds are not susceptible to PWSCC. The evaluation for determining that the tube-to-tubesheet welds are not susceptible to PWSCC will be submitted to the NRC for review and approval prior to entering the associated PEO.
Option 3: Analysis-Pressure Boundary Perform an analytical evaluation of the steam generator tube-to-tubesheet welds redefining the reactor coolant pressure boundary of the tubes, where the steam generator tube-to-tubesheet welds are not required to perform a reactor coolant pressure boundary function. The redefinition of the reactor coolant pressure boundary will be submitted to the NRC for review and approval prior to entering the associated PEO.
In the case of the applicant choosing Option 2 for Enhancement 1 and Option 2 or 3 for Enhancement 2, the staff is to review and approve the analysis prior to Byron and Braidwood entering PEO.
Issue:
The applicant did not provide a period when the analysis will be provided to the staff for review and approval. The LRA states that the analysis will be provided before PEO. In order for the staff to complete its review of such an analysis before PEO, adequate time needs to be provided for the review.
Request:
Please provide a period by which the analytical evaluation will be provided to the staff such that the staff will have adequate time to review it before Byron and Braidwood enters PEO.
Discussion: The applicant and staff discussed what would constitute a reasonable time period for NRC review of the analysis. The applicant also inquired whether this time period should be applicable to Enhancement 2 Option 3, which also includes the submittal of an analysis for staff review and approval. It was agreed that a staff review time period should be provided; therefore, the request and background sections of the ORAl were updated. This DRAI will be sent as a formal RAI titled "RAI 8.2 10.1."