ML20266G220
| ML20266G220 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 09/15/2020 |
| From: | Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation |
| Brown E, NRR/DORL/LPL2-1, 4152315 | |
| References | |
| Download: ML20266G220 (13) | |
Text
1 NRC Brief Turkey Point Unit 4 Component Cooling Water (CCW)
Supply and Return Piping Relief Request No. 7 September 15, 2020
2 Agenda Introduction
Background
Relief Request PMCap Design and Welding Flaw Characterization and Evaluation Future Monitoring Schedule Open Discussion
3 Background
- The reason for requesting relief is to repair certain sections of the Unit 4 Component Cooling Water (CCW) supply and return piping by installing a welded proprietary repair device (PMCaps Restoration Method-US Patent 6,860,297) to these moderate energy Class 3 pressure boundary piping with new pressure boundary material without removing the sections of degraded piping.
4 Background
- The extent of the CCW piping repairs due to corrosion is unknown at this time.
- The repair area of piping will be characterized using NDE techniques during the upcoming Turkey Point Unit 4 refueling outage, scheduled to start on October 3, 2020.
Upon discovery of the actual conditions of the piping, FPL will promptly provide supplemental information with sufficient details to support NRCs review and approval of this relief request.
- Due to the unknown circumstances surrounding this relief request, FPL is requesting approval, as applicable and as required, after the start of the Unit 4 refueling outage.
5 Relief Request No. 7 Relief is requested from the requirements of IWA-4421 to remove defects in accordance with IWA-4411, IWA-4461 or IWA-4462 on the CCW supply and return piping, as required, prior to performing repair/replacement activities.
Relief is also requested from the prohibition of IWA-4340 in 10 CFR 50.55a(b)(2)(xxv),
Mitigation of Defect by Modification.
RR No. 7 is similar to Relief Request No. 6 previously approved by NRC for Turkey Point Unit 3 (ML20111A279)
6 Relief Request Proposed Alternate The proposed alternate is developed after determining that other repair/replacement options that comply with IWA-4421 would create a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Turkey Point Unit 4 CCW Supply and Return Lines, as Applicable
- Request for relief will be established following the NDE inspection of the CCW supply and return lines.
- Relief is requested for the installation of the PMCap as a Mitigation of Defect by Modification (IWA-4340) and relief to not remove the defect prior to performing the repair/replacement activities (IWA-4421, IWA-4411, IWA-4461 or IWA-4462).
7 Weld Detail Weld Process - Combination of GTAW and SMAW (GTAW Root/SMAW Fill)
Preheat - Ambient (>50F)
PWHT - Not required by construction code due to thickness.
NDE - Visual and Surface (MT or PT)
Exams of Root and Final for all fabrication and installation groove welds.
PMCap Design and Weld Detail
8 Flaw Characterization Utilizing ASME Code Case N-513-4 as Guidance Piping Design
- CCW supply and return piping is designed to ANSI B31.1 1973 Edition through Winter 1976 Addendum.
- CCW supply and return Piping is classified as Quality Group C, which is considered as Class 3 under ASME Section XI.
- Design Pressure 150 psig
- Design Temperature 200 deg. F
- Pipe minimum required wall thickness is 0.135
- Elbow minimum required wall thickness varies between 0.193 and 0.229, depending on which train.
Flaw Characterization
- Flaw will be characterized by physical measurement
- The entire circumference will be inspected via visual and ultrasonic techniques
9 Flaw Evaluation Utilizing ASME Code Case N-513-4 as Guidance Evaluation Methodology
- Methods given in ASME Section XI, Appendix C.
- Linear Elastic Fracture Mechanics (LEFM) criteria employed per Article C-7000
- Allowable through-wall flaw lengths are determined by iteration comparing calculated stress intensity factors to a critical fracture toughness defined in C-7200 of Section XI, Appendix C.
Evaluation of Flaw will be performed prior to seeking relief after flaw characterization
10 Pipe Stress Analysis Pipe Stress Analysis (for each CCW Pipe) will verify that:
- The combination of the existing CCW Pipe and the PMCap addition pipe stresses remains within the allowable code stress limits.
- The PMCap addition has no adverse structural effect on the CCW Piping Integrity.
- The additional loads on the upstream and downstream supports remain acceptable.
11 Prevention and Future Monitoring After installation of the PMCap, the CCW piping and PMCaps will be applied with an aluminum oxide thermal spray coating to prevent future corrosion.
To facilitate future Inservice Inspection Program activities, a hole will be drilled into the underlying CCW piping to pressurize the annulus between the pipe and PMCap.
Future NDE will be in accordance with ASME Code,Section XI, Table IWD-2500-1 for Examination Category D-A. The piping internal of the PMCap boundary is inaccessible and will not be examined in the future because credit will no longer be taken for its pressure retaining function, thus it will be outside the Inservice Examination requirements of Section XI of the ASME Code.
12 Schedule Planned Submission of Relief Request No. 7: By 9/18/2020 Unit 4 RFO Starts on October 3, 2020 CCW PMCap Planned Activities
- 4A CCW Train Perform UT Inspection (Planned start 10/09/2020 complete 10/10/2020)
Install PM Cap ( Planned start 10/10/2020 complete 10/17/2020)
- 4B CCW Train Perform UT Inspection (Planned start 10/20/2020 complete 10/21/2020)
Install PM Cap ( Planned start 10/21/2020 complete 10/28/2020)
13 Questions