ML25349A095
| ML25349A095 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 12/15/2025 |
| From: | Bina S Plant Licensing Branch 1 |
| To: | Donell A, Para W Constellation Energy Generation, Constellation Nuclear |
| References | |
| EPID L-2025-LRO-0054 | |
| Download: ML25349A095 (0) | |
Text
1 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CALVERT CLIFFS UNIT 2 SG TUBE INSPECTION REPORT REVIEW CONSTELLATION ENERGY GENERATION, LLC CALVERT CLIFFS, UNIT 2 DOCKET NO. 05000318 ISSUE DATE: December 15, 2025
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Background===
By letter dated September 8, 2025 (Agencywide Documents Access and Management System Accession No. ML25251A026), Constellation Energy Generation, LLC (the licensee), submitted information summarizing the results of the spring 2025 steam generator (SG) inspections performed at Calvert Cliffs Nuclear Power Plant (CCNPP), Unit 2. These inspections were performed during refueling outage 26 (CC2R26).
Section 5.6.9 in the CCNPP, Unit 2, Technical Specifications (TS) requires that a report be submitted within 180 days after the initial entry into hot shutdown (MODE 4) following completion of an inspection of the SGs in accordance with TS Section 5.5.9. To complete its review of the inspections, the U.S. Nuclear Regulatory Commission (NRC) staff requests the following additional information:
Question 1 In the section entitled, Lattice Grid Wear OA [Operational Assessment], the CC2R26 report states, Adding this uncertainty to the best estimate value of 24.66% TW [through wall] from the previous paragraph yields a bounding real depth of 31.54% TW returned to service. This hypothesized real depth of 24.66%TW must then be grown at an upper 95th growth rate for the next 8.0 EFPY [Effective Full Power Years]. As discussed above, a growth rate of 2.0%TW per EFPY will be used. Applying a growth of 16.0%TW (2.0 %TW/EFPY x 8.0 EFPY) gives a bounding real depth at the end of the upcoming inspection interval of 40.66%TW (PDF pg. 15).
In addition, Table 8 of the CC2R26 report includes a 41 percent TW maximum predicted depth after four cycles for lattice grid support wear. It appears to the NRC staff that the hypothesized real depth to be grown for the next 8.0 EFPY is 31.54 percent TW instead of 24.66 percent TW.
This results in a maximum predicted depth after four cycles for lattice grid support wear of 47.54 percent TW instead of 40.66 percent TW. Please confirm the NRC staffs understanding that the maximum predicted depth after four cycles for lattice grid support wear is 47.54 percent TW (31.54 percent TW (hypothesized real depth) plus 16 percent TW (growth rate))
Question 2 The CC2R26 report states, Twenty-seven (27) foreign object [FO] wear indications were detected in.3 tubes (PDF pg. 8). However, Table 5 of the CC2R26 report includes 27 FO wear indications in 22 tubes. In addition, the NRC staff noted that a 19 percent TW FO wear indication in SG22 (Tube Row 17, Column 1 (R17C1)) was reported in the refueling outage 23 (CC2R23) report (Table 5, PDF pg. 9). However, this FO wear indication was not reported in the CC2R26 report. Tube R17C1 in SG22 does not appear to have been plugged in either CC2R23 or CC2R26. Please address the following:
2
- 1. Confirm the total number of FO wear indications and the total number of tubes containing FO wear indications.
- 2. Discuss why the 19 percent TW FO wear indication in Tube R17C1 in SG22 was not reported in the CC2R26 report.
OFFICE NRR/DORL/LPL1/PM NRR/DNRL/NCSG/BC NAME SBina SBloom DATE 11/25/2025 11/20/2025