ML20352A156
| ML20352A156 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/21/2020 |
| From: | Robert Kuntz Plant Licensing Branch III |
| To: | Domingos C Northern States Power Co |
| Kuntz R | |
| References | |
| EPID L-2019-LRO-0107 | |
| Download: ML20352A156 (3) | |
Text
December 21, 2020 Mr. Christopher P. Domingos Site Vice President Northern States Power Company - Minnesota Prairie Island Nuclear Generating Plant 1717 Wakonade Drive East Welch, MN 55089
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 1 - REVIEW OF THE 2018 STEAM GENERATOR TUBE INSPECTION REPORT (EPID L-2019-LRO-0107)
Dear Mr. Domingos:
By letter dated April 18, 2019 (Agencywide Documents Access and Management System Accession No. ML19108A291), Northern States Power Company, doing business as Xcel Energy (the licensee), submitted information summarizing the results of the 2018 steam generator inspections at Prairie Island Nuclear Generating Plant, Unit 1.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided and concludes that the licensee provided the information required by their technical specifications and that no follow-up is required at this time. The NRC staffs review is enclosed.
If you have any questions, please contact me at 301-415-3733 or via e-mail at Robert.Kuntz@nrc.gov.
Sincerely,
/RA/
Robert F. Kuntz, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-282
Enclosure:
Review of the 2018 Steam Generator Report cc: Listserv
Enclosure REVIEW OF THE 2018 STEAM GENERATOR TUBE INSPECTION REPORT NORTHERN STATES POWER COMPANY - MINNESOTA PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 1 DOCKET NO. 50-282 By letter dated April 18, 2019 (Agencywide Documents Access and Management System Accession No. ML19108A291), Northern States Power Company, doing business as Xcel Energy (the licensee), submitted information summarizing the results of the 2018 steam generator (SG) inspections at Prairie Island Nuclear Generating Plant (Prairie Island), Unit 1.
These inspections were performed during the 31st refueling outage (RFO 31).
Prairie Island, Unit 1 has two Framatome/AREVA model 56/19 replacement recirculating SGs.
Each SG has 4,868 thermally treated Alloy 690 tubes, which have a nominal outside diameter of 0.750 inches and a nominal wall thickness of 0.043 inches. The tubes were hydraulically expanded at each end for the full depth of the tubesheet. The tubes are supported by tube support plates (TSPs) and anti-vibration bars (AVBs). All TSPs are constructed from Type 410 stainless steel. The TSPs have a minimum thickness of 1.18 inches and have quatrefoil-shaped holes through which the tubes pass. The AVBs are constructed from Type 405 stainless steel and are rectangular in cross section (0.5 inches by 0.3 inches).
The licensee provided the scope, extent, methods, and results of the SG tube inspections in the letter referenced above. In addition, the licensee described corrective actions (e.g., tube plugging), if any were taken in response to the inspection findings.
After reviewing the information provided by the licensee, the U.S. Nuclear Regulatory Commission (NRC) staff has the following comments/observations:
During the RFO 31 SG tube inspections, the upper 95th percentile growth rates decreased slightly for AVB wear and increased slightly for TSP wear, as compared to the previous inspections in RFO 28 (2012), and the actual number of indications reported in RFO 31 was less than the number projected in the RFO 28 Operational Assessment.
Secondary side inspections were performed during RFO 30 and minor degradation of the loose parts trapping screen was detected in two grid locations. The degradation was dispositioned as acceptable for one cycle of operation. During the RFO 31 inspection, one additional grid with degradation was discovered. All three grids were replaced during RFO 31.
Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their technical specifications. In addition, the staff concludes that there are no technical issues that warrant follow-up action currently, since the inspections appear to be consistent with the objective of detecting potential tube degradation and the inspection results appear to be consistent with industry operating experience at similarly designed and operated units.
ML20352A156 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NCSG/BC NAME RKuntz SRohrer (JBurkhardt for)
SBloom DATE 12/17/2020 12/17/2020 12/16/2020 OFFICE NRR/DORL/LPL3/BC NRR/DORL/LPL3/PM NAME NSalgado (SWall for)
RKuntz DATE 12/21/2020 12/21/2020