ML23115A401
| ML23115A401 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 04/26/2023 |
| From: | Siva Lingam Plant Licensing Branch IV |
| To: | Heflin A Arizona Public Service Co |
| Lingam S, 301-415-1564 | |
| References | |
| EPID L-2022-LRO-0145 | |
| Download: ML23115A401 (1) | |
Text
April 26, 2023 Mr. Adam C. Heflin Executive Vice President/
Chief Nuclear Officer Mail Station 7605 Arizona Public Service Company P.O. Box 52034 Phoenix, AZ 85072-2034
SUBJECT:
PALO VERDE NUCLEAR GENERATING STATION, UNIT 1 - REVIEW OF THE 2022 STEAM GENERATOR TUBE INSPECTIONS DURING REFUELING OUTAGE 23 (EPID L-2022-LRO-0145)
Dear Mr. Heflin:
By letter dated November 4, 2022, as supplemented by letter dated February 17, 2023, Arizona Public Service Company (the licensee) submitted information summarizing the results of the spring 2022 steam generator tube inspections performed at Palo Verde Nuclear Generating Station (Palo Verde), Unit 1. These inspections were performed during Refueling Outage 23.
The steam generator tube inspection report was submitted in accordance with Technical Specification (TS) 5.6.8, Steam Generator Tube Inspection Report.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the submittal, as supplemented, and concludes that the licensee provided the information required by Palo Verde, Unit 1, TS 5.6.8. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up actions at this time. Enclosed is the NRC staffs review of the Palo Verde, Unit 1, steam generator tube inspection report.
If you have any questions, please contact me at (301) 415-1564 or via e-mail to Siva.Lingam@nrc.gov.
Sincerely,
/RA/
Siva P. Lingam, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN 50-528
Enclosure:
Review of Steam Generator Tube Inspection Report cc: Listserv
Enclosure REVIEW OF THE SPRING 2022 STEAM GENERATOR TUBE INSPECTIONS PERFORMED DURING REFUELING OUTAGE 23 ARIZONA PUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION, UNIT 1 DOCKET NO. STN 50-528 By letter dated November 4, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22308A166), as supplemented by letter dated February 17, 2023 (ADAMS Accession No. ML23048A320), Arizona Public Service Company (the licensee) submitted information summarizing the results of the spring 2022 steam generator (SG) tube inspections performed at Palo Verde Nuclear Generating Station (Palo Verde), Unit 1. These inspections were performed during Refueling Outage (RFO) 23.
Palo Verde, Unit 1, has two replacement SGs designed by Combustion Engineering and manufactured by Asea Brown Boveri Ltd (ABB)/Ansaldo. Each SG contains 12,580 thermally treated Alloy 690 tubes with an outside diameter of 0.750 inches and a wall thickness of 0.042 inches. Ferritic stainless steel eggcrate tube supports, diagonal bars, and vertical straps support the tubes at various locations.
The licensee provided the scope, extent, methods, and results of the SG tube inspections in the letter dated November 4, 2022, as supplemented by letter dated February 17, 2023. In addition, the licensee described corrective actions (e.g., tube plugging), if any were taken in response to the inspection findings.
Based on the review of the information provided, the U.S Nuclear Regulatory Commission (NRC) staff has the following observations:
During Unit 1 RFO 23, the licensee performed partial length bobbin probe inspections due to black sludge on the inside diameter of tubes in SG 12. In the supplemental letter dated February 17, 2023, the licensee clarified that both SGs 11 and 12 contain black sludge inside the tubes and the black sludge was first noted during Unit 1 RFO 19 (spring 2016). The licensee stated that the black sludge was not limited to any group or region of tubes in the SGs. The licensee compared noise monitoring values from Unit 1 RFO 21 and Unit 1 RFO 23 in both SGs 11 and 12 and confirmed no increase in noise due to the black sludge. While the origin of the black sludge is still under investigation, the licensee stated that it is assumed to be reactor coolant system (RCS) corrosion and wear products that are released after reactor shutdown and prior to peroxide injections.
A sample tested during Unit 1 RFO 19 showed that the sludge is primarily chromium, nickel, and iron in the form of nickel iron chromium spinel that is found in RCS deposits.
The licensee stated that a high impact team is being established to develop black sludge mitigating strategies.
In the supplemental letter dated February 17, 2023, the licensee clarified that a total of 196 and 193 tubes have been plugged in SGs 11 and 12, respectively.
Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant additional follow-up action at this time 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.
- concurrence by email **SE memorandum by email OFFICE NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/LA*
NRR/DNRL/NCSG/BC**
NAME SLingam PBlechman SBloom DATE 4/25/2023 4/25/2023 4/25/2023 OFFICE NRR/DORL/LPL4/BC*
NRR/DORL/LPL4/PM*
NAME JDixon-Herrity SLingam DATE 4/26/2023 4/26/2023