ML25161A218
| ML25161A218 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/10/2025 |
| From: | Justin Poole Plant Licensing Branch III |
| To: | Britting J, Schultheis M Holtec Decommissioning International |
| Wall S | |
| References | |
| EPID L-2025-LLA-0027 | |
| Download: ML25161A218 (4) | |
Text
From:
Justin Poole To:
Michael Schultheis; Johann Britting Cc:
Marlayna Doell; Ilka Berrios; ext_Amy _Filbrandt
Subject:
Request for Additional Information RE: Leak-Before-Break Amendment L-2025-LLA-0027 Date:
Tuesday, June 10, 2025 9:14:00 AM Attachments:
RAI-10625-R1.pdf Mike/Johann,
By letter dated February 5, 2025, as supplemented by letter dated February 27, 2025 (Agencywide Documents Access and Management System Accession Nos.
ML25035A216 and ML25058A265, respectively), Holtec Palisades, LLC submitted a license amendment request to the U.S. Nuclear Regulatory Commission (NRC) for the Palisades Nuclear Plant (PNP). The proposed amendment request would revise the licensing basis to include leak-before-break methodology for primary coolant system hot and cold leg loop piping.
On May 20, 2025, the NRC staff sent the licensee DRAFT RAIs to ensure that the questions are understandable, the regulatory basis is clear, there is no proprietary information contained in the RAIs, and to determine if the information was previously docketed. On June 9, 2025, the NRC and the licensee held a clarification call to discuss the DRAFT RAIs.During the call, a 30-day from the date of this email to respond to the RAIs was agreed upon.The attached is the final version of the RAIs.
These RAIs will be put in ADAMS as a publicly available document.
Justin C. Poole Project Manager Palisades, TMI, Duane Arnold Restart NRR/DORL/LPL 3 U.S. Nuclear Regulatory Commission (301)415-2048
1 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PALISADES - LAR TO INCLUDE LEAK BEFORE BREAK METHODOLOGY FOR PRIMARY COOLANT HOT AND COLD LEG PIPING HOLTEC DECOMMISSIONING INTERNATIONAL, LLC PALISADES NUCLEAR PLANT DOCKET NO. 05000255
=
Background===
By letter dated February 5, 2025, as supplemented by letter dated February 27, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession Nos.
ML25035A216 and ML25058A265, respectively), Holtec Palisades, LLC submitted a license amendment request for Palisades Nuclear Plant. The proposed amendment request would revise the licensing basis to include leak-before-break methodology for primary coolant system hot and cold leg loop piping.
Regulatory Basis 10 CFR 50.36(c)(2)(i) states in part that (i) Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a limiting condition for operation of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.
10 CFR 50, Appendix A General Design Criteria, Criterion 30Quality of reactor coolant pressure boundary states the following: Components which are part of the reactor coolant pressure boundary shall be designed, fabricated, erected, and tested to the highest quality standards practical. Means shall be provided for detecting and, to the extent practical, identifying the location of the source of reactor coolant leakage.
10 CFR 50, Appendix A General Design Criteria, Criterion 4Environmental and dynamic effects design bases states the following: Structures, systems, and components important to safety shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including loss-of-coolant accidents. These structures, systems, and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit. However, dynamic effects associated with postulated pipe ruptures in nuclear power units may be excluded from the design basis when analyses reviewed and approved by the Commission demonstrate that the probability of fluid system piping rupture is extremely low under conditions consistent with the design basis for the piping.
RAI-1
Issue:
The Limiting Condition for Operation (LCO) for Palisades Technical Specifications (TS) 3.4.13, PCS Operational LEAKAGE, requires primary coolant system (PCS) operational LEAKAGE for unidentified LEAKAGE be limited to 1 gallon per minute (gpm). Regulatory Guide 1.45,
2 Revision 1, Regulatory Position 2.2 states that The plant should use leakage detection systems with a response time (not including the transport delay time) of no greater than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for a leakage rate of 1 gal/min (3.8 L/min).
Palisades TS 3.4.15, PCS Leakage Detection Instrumentation, requires operability of three of the following PCS leakage detection instrumentation channels:
- 1. One containment sump level indicating channel;
- 2. One containment atmosphere gaseous activity monitoring channel;
- 3. One containment air cooler condensate level switch channel;
- 4. One containment atmosphere humidity monitoring channel.
The licensee provided sufficient information for the containment sump level indication regarding its ability to detect the required leakage rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. However, the ability of the other 3 TS required instruments to detect the required leakage is not sufficiently demonstrated:
Containment atmosphere gaseous activity monitor: Enclosure to the LAR states that the containment atmosphere gaseous activity monitor is capable of detecting a 100 cm 3 /min leak in 45 minutes based on 1% failed fuel (100 cm 3 /min is equivalent to
~0.03 gpm). However, as stated in NRC Information Notice 2005-24, Nonconservatism in Leakage Detection Sensitivity, (ML051780073) because of improvements in fuel performance and reactor coolant system chemistry control, the actual reactor coolant system source term can be orders of magnitude smaller than that for 1 percent failed fuel challenging the capability of the gaseous activity monitor for detecting leakage rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Considering the uncertainty of the fraction of failed fuel, the LAR does not provide information on how the activity monitor can detect a leakage rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
Containment air cooler condensate level switch: Enclosure to the LAR states that If leakage flow to the sump pan is greater than 20 gpm, the level in the sump pan will rise to the liquid level switch and trigger an alarm in the control room at +6" from the bottom of the sump pan. The LAR does not provide information on how the level switch can detect a leakage rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
Containment atmosphere humidity detectors: Enclosure to the LAR states that Each of 4 humidity detectors is capable of detecting a change of humidity of 10% which would result from approximately 150 gallons of primary water leakage. This equals a leak rate sensitivity of 2.5 gpm in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, which is below the leakage rate sensitivity of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. The LAR does not provide information on how the humidity detectors can detect a leakage rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
Request:
Demonstrate that the TS listed components (TS 3.4.15 instrumentations b, c, and d) can detect a leakage rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> as stated in Regulatory Guide 1.45, Revision 1, Regulatory Position 2.2, as a way to be in compliance with 10 CFR App A GDC 30.
RAI-2
Issue:
Holtec explained that the proposed change would eliminate the need to account for the dynamic effects associated with high-energy pipe rupture in the PCS piping from the licensing and design bases of Palisades, consistent with 10 CFR 50, Appendix A, General Design Criteria (GDC) 4.
3 Specifically, the enclosure to the LAR addresses the description and evaluation of proposed changes. To complete its review, the NRC staff requests the following additional information.
Request:
Section 2.4 of the enclosure to the LAR states that the proposed change will allow the elimination of large break asymmetric dynamic loads in the PCS hot-leg and cold-leg piping from the licensing basis. Given the omission of the crossover-leg main loop piping in the discussion on the LBB scope, clarify whether the LBB methodology is applied to the crossover-leg main loop piping (also called primary loop piping).
RAI-3
Issue:
Section 3.1.2 of the enclosure to the LAR indicates that the safe ends on the subject primary loop piping consist of cast stainless steel (CSS). However, it is not clear to the staff how Holtec considered the thermal aging effect of the 60-year operation on the fracture toughness (FT) of the CSS safe ends in the LBB analysis.
Request:
Please clarify the following: (1) how Holtec considered the thermal aging effect of the 60-year operation on the FT properties of the CSS safe ends in the LBB analysis; and (2) whether the FT properties used in the LBB analysis are the saturated properties that can represent the 60-year FT properties and, if not, explanation for why the use of unsaturated FT properties is adequate.
RAI-4
Issue:
In Section 3.1.4 of the enclosure to the LAR, Holtec indicates that the likelihood of primary water stress corrosion cracking (PWSCC) in the PCS main loop piping is eliminated due to the absence of any Alloy 600/82/182 materials of construction in the PCS main loop piping and connection welds.
In contrast, the following reference indicates that Palisades has PWSCC-susceptible Alloy 82/182 dissimilar metal welds at the reactor coolant pump (RCP) inlet and outlet nozzles
(
Reference:
Technical Letter Report TLRRES/DE/REB202114R1, Probabilistic Leak-Before-Break Evaluations of Pressurized-Water Reactor Piping Systems using the Extremely Low Probability of Rupture Code, April 2022, Section 2.1 and Table 2-1, ADAMS Accession No. ML22088A006).
Request:
Please resolve the apparent inconsistency discussed above regarding the presence of PWSCC-susceptible materials in the Palisades main loop piping. If there is a PWSCC-susceptible material at the RCP inlet or outlet nozzle location, provide the evaluation of the potential impact of the PWSCC-susceptible material on the LBB application.