ML25128A187
| ML25128A187 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/08/2025 |
| From: | Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25128A184 | List: |
| References | |
| RS-25-093 | |
| Download: ML25128A187 (1) | |
Text
May 8, 2025 Enclosure B Page 1 of 8 Enclosure B Dresden Nuclear Power Station, Units 2 and 3, Subsequent License Renewal Application Updates Resulting from RAI responses
==
Introduction:==
This enclosure provides SLRA updates that resulted from the responses to RAIs Set 2, organized according to the following table of contents:
RAI 4.3.6-1..2 RAI B.2.1.33-24 RAI B.2.1.33-17 For clarity, entire sentences or paragraphs from the SLRA are provided with the deleted text highlighted by strikethroughs and the inserted text highlighted by bolded italics. In addition, any revisions to the SLRA tables are shown by providing excerpts from the affected tables.
May 8, 2025 Enclosure B Page 2 of 8 As a result of the response to RAI 4.3.6-1 provided in Enclosure A of this letter, SLRA Section 4.3.6.2, Unit 2 Jet Pump Riser Repair/Mitigation Clamps Thermal Fatigue Analysis, page 4.3-27 is revised as shown below.
4.3.6.2 Unit 2 Jet Pump Riser Repair/Mitigation Clamps Thermal Fatigue Analysis TLAA
Description:
During the fall 2001 refueling outage for DNPS Unit 2, a crack was detected on the RB-4b leaf brace to block weld to the in the jet pump riser brace (JPRB) for Jet Pumps 9/10 9 and 10. A mechanical repair clamp clamping system designed to structurally replace this weld these welds was installed on both jet pump risers in 2003. Also in 2003, vibration mitigation clamps Mitigation clamps were also installed on the remaining other 19 JPRBs leaf braces, resulting in an increase in the first and second mode natural frequencies, precluding high cycle fatigue cracking concerns. The design of this modification included a fatigue evaluation for the one mechanical repair clamp and the 19 vibration mitigation clamps JPRB clamps based on an assumed number of startup transient occurrences over a 40-year design life and resulting in a fatigue usage of 0.04.
Since the thermal fatigue cycles were assumed through a 40-year service life concluding in 2043, and the subsequent period of extended operation ends in 2049, the analysis has been identified as a TLAA that requires evaluation for the SPEO.
TLAA Evaluation:
A fatigue evaluation was performed and reported in the original hardware stress report and has been re-evaluated in a proprietary GEH report to extend the JPRB clamps service life from a 40-year to 50-year service life through 2053.
The fatigue evaluation considered the horizontal differential thermal expansion between the RPV and the jet pump assembly. The highest alternating stresses were calculated. The corresponding allowable alternating cycles were then established. In addition, the number of assumed startup transient occurrences were scaled up from a 40-year design life to a 50-year design life. The resultant fatigue usage would equate to 0.05 which is significantly less than the allowable fatigue usage of 1.0.
The SLR application for DNPS Unit 2 will extend the SPEO through 2049. The design life analyzed for the mechanical repair clamp and the 19 vibration mitigation clamps JPRB clamps and components are valid through at least 2053, as discussed above. Therefore, the JPRB clamp thermal fatigue analysis remains valid through the SPEO.
TLAA Disposition: 10 CFR 54.21(c)(1)(ii) - The DNPS Unit 2 Jet Pump Riser Brace mechanical repair clamp and the vibration mitigation clamps clamps thermal fatigue analysis has been revised to remain valid through the SPEO.
May 8, 2025 Enclosure B Page 3 of 8 As a result of the response to RAI 4.3.6-1 provided in Enclosure A of this letter, SLRA Section A.4.3.8, Unit 2 Jet Pump Riser Repair/Mitigation Clamps Thermal Fatigue Analysis, page A-62 is revised as shown below.
A.4.3.8 Unit 2 Jet Pump Riser Repair/Mitigation Clamps Thermal Fatigue Analysis During the fall 2001 refueling outage for DNPS Unit 2, a crack was detected on the RB-4b leaf brace to block weld to in the jet pump riser brace (JPRB) for Jet Pumps 9/10 9 and 10. A mechanical repair clamp clamping system designed to structurally replace this weld these welds was installed on both jet pump risers in 2003., Also in 2003, vibration mitigation clamps and mitigation clamps were installed on the remaining other 19 JPRBs leaf braces, precluding high cycle fatigue cracking concerns. The design of this modification included a fatigue evaluation based on a 40-year design life, which has been identified as a TLAA that requires evaluation for the SPEO.
The fatigue evaluation performed and reported in the original hardware stress report has been re-evaluated in a proprietary GEH report to extend the JPRB clamps service life from a 40-year to 50-year service life through 2053. The resultant fatigue usage is significantly less than the allowable fatigue usage of 1.0. Since the SLR application for DNPS Unit 2 will extend the PEO SPEO through 2049, the Unit 2 JPRB clamps thermal new fatigue analysis has been revised to remains valid through the SPEO in accordance with 10 CFR 54.21(c)(1)(ii).
May 8, 2025 Enclosure B Page 4 of 8 As a result of the response to RAI B.2.1.33-2 provided in Enclosure A of this letter, SLRA Section 3.5.2.1.2, Component Supports, page 3.5-4, as modified in CEG letter DNPS Supplement No. 2, dated March 13, 2025, is revised as shown below:
3.5.2.1.2 Component Supports Materials The materials of construction for the Component Supports components are:
Aluminum Carbon and Low Alloy Steel Bolting Carbon Steel Concrete Elastomer Galvanized Bolting Galvanized Steel Grout High Strength Low Alloy Steel Bolting with Yield Strength of 150 ksi or Greater Lubrite Reinforced concrete Stainless Steel Stainless Steel Bolting Environments The Component Supports components are exposed to the following environments:
Air - Indoor, Uncontrolled Air - Outdoor Groundwater/Soil Treated Water Water - Flowing
May 8, 2025 Enclosure B Page 5 of 8 As a result of the response to RAI B.2.1.33-2 provided in Enclosure A of this letter, SLRA Table 3.5.2-2, Component Supports Summary of Aging Management Evaluation, page 3.5-120, as modified in CEG letter DNPS Supplement No. 2, dated March 13, 2025, is revised as shown below:
Component Type Intended Function Material Environment Aging Effect Requiring Management Aging Management Programs NUREG-2191 Item NUREG-2192 Table 1 Item Notes Supports for Raceways, Cable Trays, Conduit, HVAC Ducts, Tube Track, Instrument Tubing, Non-ASME Piping and Components (Support members; welds; bolted connections; support anchorage to building structure)
Structural Support Galvanized Steel Air - Indoor, Uncontrolled None None III.B2.TP-8 3.5.1-095 A
Air - Outdoor Loss of Material Structures Monitoring (B.2.1.33)
III.B2.TP-6 3.5.1-093 A
Water - Flowing Loss of Material Structures Monitoring (B.2.1.33)
H, 4
May 8, 2025 Enclosure B Page 6 of 8 As a result of the response to RAI B.2.1.33-2 provided in Enclosure A of this letter, plant specific note for SLRA Table 3.5.2-2, Component Supports Summary of Aging Management Evaluation, page 3.5-125, as modified in CEG letter DNPS Supplement No. 2, dated March 13, 2025, is revised as shown below:
Plant Specific Notes:
- 1. The columns that support the torus saddles use epoxy grout in the anchor bolt holes under the base plates. The anchor bolts are not preloaded in order to facilitate sliding on the Lubrite plates that are on top of the base plate and below the bottom of the column. The anchor bolts and epoxy grout are not subject to high temperatures or high radiation levels. This epoxy grout in an air - indoor uncontrolled environment is considered to be similar to cementitious grout in an air - indoor uncontrolled environment for this line item and has the same aging effects.
- 2. The Structures Monitoring (B.2.1.33) is substituted to manage loss of material of the carbon steel non-ASME IWF supports exposed to treated water.
- 3. The ASME Section XI, Subsection IWF (B.2.1.30) AMP is used to manage loss of fracture toughness for the reactor vessel skirt and reactor vessel to reactor shield wall stabilizer. See further evaluation 3.5.2.2.2.6 for evaluation of irradiation effects that might lead to a loss of fracture toughness.
- 4. The Structures Monitoring AMP (B.2.1.33) is used to manage loss of material for the galvanized steel cable trays in the Units 2 and 3 Crib House since there is significant water in-leakage and, therefore, the service environment is classified as Water -
Flowing.
May 8, 2025 Enclosure B Page 7 of 8 As a result of the response to RAI B.2.1.33-2 and RAI B.2.1.33-1 provided in Enclosure A of this letter, SLRA Appendix A, Section A.2.1.33, Enhancement 18 and Enhancement 19 on page A-38 of the SLRA is added as shown below:
- 18. Replace the degraded components of the cable tray assembly to restore the assembly to full structural design capacity. This will be performed prior to entering the subsequent period of extended operation and every 20 years thereafter.
- 19. Perform detailed evaluation of the Units 2 and 3 chimney in accordance with section 5.3 of ACI 349.3R-02.
- a. Perform the initial detailed evaluation using the quantitative results obtained during the baseline inspections.
- b. Identify material testing, supplemental inspections, and other corrective actions needed to establish degradation trend during the initial detailed evaluation.
- c. Perform the final detailed evaluation using the data obtained from the initial detailed evaluation.
- d. Modify future inspections and perform corrective actions as required, to ensure that the chimneys structural integrity and intended functions are maintained during the SPEO.
The program will be enhanced and the initial engineering evaluation will be completed no later than six months prior to the subsequent period of extended operation. Baseline inspections will be completed no later than the last refueling outage prior to the subsequent period of extended operation. The initial replacement of the degraded components of the cable tray assembly will be performed no later than the last refueling outage prior to the subsequent period of extended operation. The final detailed evaluation of the Units 2 and 3 chimney will be performed no later than two years after entry into the subsequent period of extended operation.
May 8, 2025 Enclosure B Page 8 of 8 As a result of the response to RAI B.2.1.33-2 and RAI B.2.1.33-1 provided in Enclosure A of this letter, SLRA Appendix B, Section B.2.1.33, Enhancement 18 and Enhancement 19 on page B-190 of the SLRA is added as shown below:
- 18. Replace the degraded components of the cable tray assembly to restore the assembly to full structural design capacity. This will be performed prior to entering the subsequent period of extended operation and every 20 years thereafter. Program Element Affected: Scope of Program (Element 1)
- 19. Perform detailed evaluation of the Units 2 and 3 chimney in accordance with section 5.3 of ACI 349.3R-02.
- a. Perform the initial detailed evaluation using the quantitative results obtained during the baseline inspections.
- b. Identify material testing, supplemental inspections, and other corrective actions needed to establish degradation trend during the initial detailed evaluation.
- c. Perform the final detailed evaluation using the data obtained from the initial detailed evaluation.
- d. Modify future inspections and perform corrective actions as required, to ensure that the chimneys structural integrity and intended functions are maintained during the SPEO.
Program Elements Affected: Parameters Monitored or Inspected (Element 3),
Detection of Aging Effects (Element 4), Monitoring and Trending (Element 5),
and Acceptance Criteria (Element 6)
The program will be enhanced and the initial engineering evaluation will be completed no later than six months prior to the subsequent period of extended operation. Baseline inspections will be completed no later than the last refueling outage prior to the subsequent period of extended operation. The initial replacement of the degraded components of the cable tray assembly will be performed no later than the last refueling outage prior to the subsequent period of extended operation. The final detailed evaluation of the Units 2 and 3 chimney will be performed no later than two years after entry into the subsequent period of extended operation.