L-2024-040, Notification of Deviation from Pressurized Water Owners Group (PWROG) Report WCAP-17451-P, Revision 1, Reactor Internals Guide Tube Wear - Westinghouse Domestic Fleet Operational Projections
| ML24088A196 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 03/28/2024 |
| From: | Catron S Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2024-040 | |
| Download: ML24088A196 (1) | |
Text
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U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington D C 20555-0001 RE:
Turkey Point Nuclear Plant, Unit 3 Docket No. 50-250 Subsequent Renewed Facility Operating License DPR-31 March 28, 2024 L-2024-040 Notification of Deviation from Pressurized Water Owners Group (PWROG) Report WCAP-17451-P, Revision 1, Reactor Internals Guide Tube Wear - Westinghouse Domestic Fleet Operational Projections
Reference:
- 1.
Pressurized Water Owners Group (PWROG) Letter OG-23-63, PWR Owners Group NEI 03-08 "Needed" Guidance: "PWR Thermal Shield Flexure Inspection Requirements," May 8, 2023.
Florida Power & Light Company (FPL) hereby provides notification of a deviation from the initial monitoring requirements provided in Reference 1, for Turkey Point Nuclear Plant Unit 3 (Turkey Point Unit 3). The deviation is from Nuclear Energy Institute (NEI) 03-08 "Needed" guidance which recommends initial neutron noise monitoring be implemented within the following period:
Initial monitoring completed prior to July 1, 2024; or Within two operating cycles of the most recent thermal shield flexure inspection NEI 03-08 provides requirements for "Needed" (versus mandatory) work product elements, allows deviations with the appropriate justification and documentation.
On February 14, 2023, FPL notified the Pressurized Water Reactor Owners Group (PWROG) of the intended deviation from the guidance included in OG-23-63 (Reference 1 ). The duration of the deviation will be the roughly three month period between the specified implementation period and the fall 2024 unit 3 outage in which the reactor vessel core barrel thermal shield flexures will be visually inspected. After this inspection, neutron noise monitoring will be required within two operating cycles, or by Spring 2028.
(Turkey Point Unit 3 intends to begin its initial 24 month fuel cycle following the Spring 2026 refueling outage.)
The attachment to this letter provides the FPL report, "Turkey Point Unit 3 - Deviation From Implementation Period For Neutron Noise Monitoring Specified in NEI 03-08 Needed Guidance Transmitted by OG-23-63."
In accordance with NEI 03-08, Revision 4, this notification is being provided for information only and no action is being requested from the NRC staff.
Should you have any questions regarding this submission, please contact Mr. Kenneth Mack, Fleet Licensing Manager, at 561-904-3635.
Florida Power & Light Company 9760 SW 344th Street, Homestead, FL 33035
Turkey Point Nuclear Plant, Unit 3 Docket No. 50-250 This letter contains no new regulatory commitments.
Sincerely, Steve Cato Licensing nd Regulatory Compliance Director - Nuclear Fleet Florida Power & Light Company cc:
USNRC Regional Administrator, Region II Project Manager, USNRC, Turkey Point Nuclear Plant Resident Inspector, USNRC, Turkey Point Nuclear Plant Mr. Clark Eldredge, Florida Department of Health L-2024-040 Page 2 of 2 Attachment -
Turkey Point Unit 3 - Deviation From Implementation Period For Neutron Noise Monitoring Specified in NEI 03-08 Needed Guidance Transmitted by OG-23-63.
Turkey Point Nuclear Plant, Unit 3 Docket No. 50-250 ATTACHMENT Turkey Point Unit 3 L-2024-040 Turkey Point Unit 3 - Deviation From Implementation Period For Neutron Noise Monitoring Specified in NEI 03-08 Needed Guidance Transmitted by OG-23-63.
(3 pages follow)
Turkey Point Unit 3 - Deviation From lmplementatfon Period For Neutron Noise Monitoring Specified In NEI 03-08 Needed Guidance Transmitted by OG-23-63 Reason for Deviation:
In May 2023, the Pressurized Water Reactor Owners Group (PWROG) issued NEI 03-08 "Needed" Guidance associated with management of reactor vessel core barrel thermal shield flexure degradation (Reference 1). The guidance requires performance of periodic or continuous neutron noise monitoring within the following implementation period:
Initial monitoring completed prior to July 1, 2024; or Within two operating cycles of the most recent thermal shield flexure inspection Turkey Point (PTN) intends to perform a visual inspection of the Unit 3 thermal shield flexures during their Fall 2024 outage. Due to the short time period between the end of the implementation period and the inspections, PTN will deviate from the "Needed" Guidance.
Deviation from Needed" guidance is governed by Reference 2.
expected Duration for which Justification/Deviation applies:
The duration of the deviation is the period between the end of the specified Implementation period (July 1, 2024) and PTN Unit 3 Fall 2024 outage PTN3-34.
Technical Justification:
The intent of the guidance provided in Reference 1 is to identify thermal shield flexure degradation at a time that prevents "rapid cascading degradation of lower internals components upon flexure failure".
Flexure failure results in increased vibratory/fatigue stresses on the core barrel and associated components. Given that the visual inspections of the flexures is performed at a 10 year interval, failu.re early in the interval could result in degradation of other components such as baffle bolts, or thermal shield support block bolts (TSSBs). Such downstream failures have occurred at multiple plants, resulting in significant.cost and outage extension.
Deviation from the "Needed" guidance for a 3 month period does not increase the risk of unidentified cascading failures, and is supported by the following technical justifications:
- 1. Low Susceptibility o
Reference 3 reports the conclusions of a PWROG funded evaluation that estimated fndustry susceptibility to thermal shield flexure degradation. The evaluation considered both thermal operating stresses, and plant operating history to estimate a fatigue usage for each plant, and ranked the units as having either "Low", "Medium" or "High" susceptibility.
o PTN Unit 3 was evaluated to have a "Low" susceptibility to flexure failure.
- 2. No Direct Impact to Safety o
The guidance states that flexure failure results in a "moderate" risk significance that contributed to then guidance's "Needed" classification.
o The thermal shleld flexures themselves provfde no safety function, and the safety significance of the component only applies to operation with failed flexures for a duration long enough to cause failure of a downstream safety significant component.
o The safety impact of flexure degradation is mitigated by a PWROG funded generic safety assessment (Reference 4) that provides a minimum one-cycle justification for continued operation for a conservatively bounding severity of the degradation.
Given that the safety assessment applies to both 18-month and 24-month operating cycles, deferring compliance with the guidance for 3 months has no impact on the applicability of the assessment to PTN1 as it is currently operating on an 18-month cycle, and the next refueling outage following Fall 2024 will occur In Spring 2026.
- 3. No Economic Impact o
Aside from the low risk significance discussed in (2) above, all other criteria that contributed to the guidance's classification of "NEEDED" are associated with the potential commercial impacts associated with flexure failure. These commercial Impacts are driven by replacement of potentially degraded downstream components (baffle bolts, TSSBs).
o Deferring compliance with the guidance for 3 months does not impact the time at which the economic impact of downstream failures will be identified, or impact the contingency preparations associated with their identification.
Conclu_slon/Flndlngs:
Deviation from the implementation period specified by the NEI 03-08 "Needed" Guidance contained In Reference 1 Is technically justified by the site's low susceptibility to thermal shield flexure failure, as well as the lack of a safety or economic impact associated with the minor deviation.
The duration of the deviation is 3 months, at which point the unit will be in compliance with the "Needed" Guidance. Initial Neutron Noise Monitoring will be required prior to PTN3-36 refueling outage. Actions have been added to the AR documenting this deviation to establish and track the monitoring requirement.
References:
- 1. Letter Number OG-23-63, PWR Owners Group NEI 03-08 Needed Guidance: "PWR Thermal Shield Flexure Inspection Requirements," May 8, 2023.
- 2. ER-AA-105, "Reactor Coolant System Materials Degradation Management Program (RCS MDMP}, Revision 10.
- 3. PWROG-21015-P, Revision 1, "Thermal Shield Flexure Susceptibility Study, December 2022.
- 4. PWROG-19003-P, Revision 1, "Clevis Insert/Radial Key Wear Assessment," May, 2021.
)L, C.,ttJi Prepared By: Shane Webb (Fleet Program Owner)/
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Executive Director Fleet Englneertng: Jack Hamm/ ~
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NRC Notification Required? Yes, Letter Number# See AR 2476676-02 IP Notification Required? Yes, Letter Number# See AR 2476676-01