ML25100A134

From kanterella
Jump to navigation Jump to search
Enclosure a: Responses to NRC Request for Additional Information Set 1 and Request for Confirmation of Information Sets 1 and 2 Related to the Dresden Nuclear Power Station, Units 2 and 3, Subsequent License Rnewal Application
ML25100A134
Person / Time
Site: Dresden  Constellation icon.png
Issue date: 04/10/2025
From:
Constellation Energy Generation
To:
Office of Nuclear Reactor Regulation
Shared Package
ML25100A132 List:
References
RS-25-049
Download: ML25100A134 (1)
v • d • e


Text

April 10, 2025 Enclosure A Page 1 of 23 Enclosure A Responses to NRC Request for Additional Information Set 1 and Request for Confirmation of Information Sets 1 and 2 related to the Dresden Nuclear Power Station, Units 2 and 3, Subsequent License Renewal Application

==

Introduction:==

This enclosure provides responses to NRC Request for Additional Information Set 1 and Request for Confirmation of Information Sets 1 and 2, organized according to the following table of contents:

Table of Contents Responses to NRC Request for Additional Information Set 1:

RAI 4.3.1-1................................................................................................................................ 2 RAI 4.3.3-1................................................................................................................................ 4 RAI 4.3.3-2................................................................................................................................ 9 RAI 4.3.4-1...............................................................................................................................12 RAI 4.3.5-1...............................................................................................................................17 Responses to NRC Request for Confirmation of Information Set 1:

RCI B.2.1.28-1..........................................................................................................................20 RCI B.2.1.28-2..........................................................................................................................21 RCI B.2.1.28-3..........................................................................................................................21 RCI B.2.1.28-4..........................................................................................................................22 RCI B.2.1.28-5..........................................................................................................................22 Responses to NRC Request for Confirmation of Information Set 2:

RCI 3.3.2-1...............................................................................................................................23 RCI B.2.1.27-1..........................................................................................................................23 RCI B.2.1.11.............................................................................................................................23

April 10, 2025 Enclosure A Page 2 of 23 Responses to NRC Request for Additional Information Set 1 as follows:

RAI 4.3.1-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.

=

Background===

SLRA Tables 4.3.1-1 and 4.3.1-2 indicate the Unit 2 turbine roll and increase to rated power and the Units 2 and 3 main steam fill during flood-up transient are projected to exceed the design transient cycles before 80 years (i.e., 160 and 20 cycles, respectively). The transient cycle is also called the transient occurrence.

The applicant dispositioned the fatigue TLAAs for the isolation condensers and the Unit 2 replacement core spray piping in accordance with 10 CFR 54.21(c)(1)(i), as discussed in SLRA Sections 4.3.7 and 4.7.5, respectively.

Issue Given the TLAA dispositions for the components discussed above in accordance with 10 CFR 54.21(c)(1)(i) (i.e., not using cycle projections or Fatigue Monitoring AMP), the staff needs clarification on whether the 80-year projected cycles of the Unit 2 turbine roll and increase to rated power transient and the Units 2 and 3 main steam fill during flood-up transient, which exceed the design cycles, may affect the validity of the TLAA dispositions (e.g., resulting in the 80-year CUF values greater than 1.0).

Request Given the TLAA dispositions for the components discussed above in accordance with 10 CFR 54.21(c)(1)(i), clarify whether the 80-year projected cycles of the Unit 2 turbine roll and increase to rated power transient and the Units 2 and 3 main steam fill during flood-up transient, which exceed the design cycles, may affect the validity of the TLAA dispositions. If the validity of the TLAA dispositions is affected, explain why the applicants TLAA evaluations are acceptable.

Constellation Response:

Even though the 80-year occurrence projections for these two transients exceed the occurrence values assumed in the original calculations, the contribution of these two transients to fatigue is minor and the resulting CUF or CUFen projections for impacted components on SLRA Table 4.3.1-3 are significantly less than the ASME Section III limit of 1.0.

Transient 4 and 42 on SLRA Tables 4.3.1-1 and 4.3.1-2 were used, as input, in a limited number of original fatigue evaluations and the CUF or CUFen calculation of only 3 locations on SLRA

April 10, 2025 Enclosure A Page 3 of 23 Table 4.3.1-3 are impacted by these two transients, as explained below. The impact to fatigue of these two transients on these three locations is minor. As explained in SLRA Section 4.3.1, the assumed number of design transient occurrences does not represent a final design limit; rather, the design limit is that the CUF or CUFen value does not exceed a value of 1.0.

SLRA Table 4.3.1-1 shows that the Turbine Roll & Increase to Rated Power transient for Unit 2 (transient 4) is projected to exceed the assumed design transient occurrences number of 160 before 80 years. In addition, SLRA Table 4.3.1-1 and 4.3.1-2 show that the Main Steam Fill During Flood-up transient (transient 42) is projected to exceed the assumed design transient occurrence number of 20 before 80 years.

Transient 4 is assumed in the fatigue calculations of only components 17 and 18 on SLRA Table 4.3.1-3 and the resulting 80-year CUFen projections are significantly less than the limit of 1.0.

The exceedance of transient 4 beyond the originally assumed number of 160 occurrences is concluded to have a small impact on these two locations.

Also, transient 42 is assumed only in the fatigue calculation for component 15 on SLRA Table 4.3.1-3 and the resulting 80-year CUFen projections are significantly less than the limit of 1.0.

These two transients are not used as input to any other locations on SLRA Table 4.3.1-3 or other components described and evaluated in SLRA Sections 4.3 or 4.7.

With respect to the isolation condenser fatigue TLAA described and evaluated in SLRA Section 4.3.7, a review of the supporting basis documents for the TLAA evaluation shows that neither transient 4 nor 42 was considered in the fatigue evaluation of the isolation condensers.

With respect to the Unit 2 replacement core spray piping fatigue TLAA described and evaluated in SLRA Section 4.7.5, a review of the supporting basis documents for the TLAA evaluation shows that neither transient 4 nor 42 was considered in the fatigue evaluation of the replacement piping.

Therefore, the fatigue related TLAAs in SLRA Sections 4.3.7 and 4.7.5 dispositioned as 10 CFR 54.21(c)(1)(i) remain valid.

April 10, 2025 Enclosure A Page 4 of 23 RAI 4.3.3-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.

=

Background===

SLRA Section 4.3.3 addresses the screening EAF evaluation to determine the plant-specific EAF locations that may be more limiting than the NUREG/CR-6260 locations. The SLRA section explains that the screening evaluation uses bounding environmental fatigue correction factor (Fen) and environmentally adjusted cumulative usage factor (CUFen) values.

Issue The SLRA does not clearly discuss how the bounding Fen and CUFen values are calculated.

Specially, the following items are not clear to the staff: (1) how the bounding temperature is calculated for each location (e.g., use of the maximum temperature of the thermal zone for the component location or the component-specific maximum temperature); (2) how the bounding strain rate is calculated; and (3) how bounding sulfur content is calculated for the components fabricated with carbon or low alloy steel.

In addition, the SLRA indicated that the detailed EAF evaluation was performed to refine the CUFen values to reduce the excessive conservatism associated with the screening CUFen values. However, the SLRA does not clearly discuss how the applicant refined the CUFen values for the limiting locations.

Request

1. Discuss the following items related to the applicants approach to calculate the bounding Fen and CUFen values in the screening evaluation: (1) how the bounding temperature is calculated for each location (e.g., use of the maximum temperature of the thermal zone for the component location or the component-specific maximum temperature); (2) how the bounding strain rate is calculated; and (3) how bounding sulfur content is calculated for the components fabricated with carbon or low alloy steel.
2. Discuss how the detailed EAF evaluation refined the CUFen values by reducing the excessive conservatism associated with the screening CUFen. As part of the discussion, clarify the applicants approach used in the detailed EAF evaluation in terms of determining the transient temperature, strain rate and evaluated cycles, as compared to the approach used in the screening evaluation.

April 10, 2025 Enclosure A Page 5 of 23 Constellation Response to Request 1:

Bounding Temperature The temperature assumed in the EAF screening evaluation for each thermal zone is the maximum temperature specified in the Thermal Cycle Diagram for the thermal zone.

For example, the maximum temperature used in the EAF screening for the RPV Region A thermal zone components is 587°F. This corresponds to the maximum temperature specified on the Thermal Cycle Diagram. The Thermal Cycle Diagram documents that of all the specified transients, transient event 17 (Over Pressure 1375 psig) has a peak temperature of 587°F. All other specified temperatures for all other transients on the Thermal Cycle Diagram for the RPV Region A thermal zone are less than 587°F. Therefore, the EAF screening assumed 587°F for all RPV Region A thermal zone components.

Strain Rates and Sulfur Content For the EAF screening evaluation, sulfur content values and strain rate values were selected to result in the maximum contribution to the EAF screening Fen values.

In NUREG/CR-6909, Revision 1 the calculated Fen value for a given component is calculated using four major inputs. These are: strain rate, sulfur content, temperature, and historical dissolved oxygen concentrations. For example, NUREG/CR-6909, Revision 1 recommends that Fen values for both carbon and low-alloy steels are calculated as follows:

Fen = exp((0.003 - 0.031*) S* T* O* )

Where,
  • is strain rate parameter in Fen equations, S* is sulfur parameter in carbon steel (CS) and low alloy steel (LAS) in Fen equations, T* is temperature parameter in Fen equations, and O* is oxygen parameter in Fen equations.

The EAF screening evaluation used the most conservative sulfur content value recommended in NUREG/CR-6909, Revision 1. For example, for both carbon and low-alloy steels NUREG/CR-6909, Revision 1 recommends the following:

S* = 2.0 + 98 S (S 0.015 wt.%)

S* = 3.47 (S > 0.015 wt.%)

For the EAF screening evaluation, the value of 3.47 was selected for both carbon and low-alloy steels, since it results in the maximum contribution to Fen.

April 10, 2025 Enclosure A Page 6 of 23 In addition, the EAF screening evaluation selected strain rates with the greatest contribution to Fen. For example, for both carbon and low-alloy steels NUREG/CR-6909, Revision 1 recommends the following:

  • = 0 ( > 2.2%/s)
  • = ln(/2.2) (0.0004%/s 2.2%/s)
  • = ln (0.0004/2.2) ( < 0.0004%/s)

Where, is strain rate, %/sec For the EAF screening evaluation, the value of ln (0.0004/2.2) was selected for both carbon and low-alloy steels, since it results in the maximum contribution to Fen.

Constellation Response to Request 2:

The EAF screening evaluation assumed very conservative factors, such as the number of assumed transient occurrences and conservative operating temperatures, which resulted in significantly overly conservative CUFen values (screening 80-year CUFen values). The purpose of the evaluation was to conservatively identify bounding components and screen out components which are not bounding.

The detailed evaluation was performed per the guidance in NUREG/CR-6909, Revision 1 and accurately calculate projected CUFen values for the bounding components; consistent with the original fatigue evaluation and adjusted for EPU and EAF. The resulting calculations are then incorporated into the SI:FatigueProTM software, if required.

The "screening 80-year CUFen values calculated in the EAF screening evaluation are more conservative than the projected 80-year CUFen value developed in the detailed evaluation.

This is clarified below in terms of determining the transient temperature, strain rate and evaluated cycles for the detailed evaluation, as compared to the approach used in the EAF screening evaluation.

(1) Strain Rate:

Both the EAF screening evaluation and the detailed evaluation assumed the minimum strain rate which results in the maximum impact on Fen.

(2) Evaluated Cycles:

The calculation of the "projected 80-year CUFen" values in the detailed evaluation assumed the projected 80-year number of occurrences documented in SLRA Table 4.3.1-1 and 4.3.1-2. SLRA Tables 4.3.1-1 and 4.3.1-2 show that the projected number of occurrences for 80 years are less than the number of occurrences originally assumed, with two minor exceptions which are discussed in the response to RAI 4.3.1-1.

April 10, 2025 Enclosure A Page 7 of 23 Except for the Isolation Condensers (ISCO), in the EAF screening methodology the screening 80-year CUFen values were scaled from the original design CUF values by a factor of 2, if the original fatigue calculation assumed 40 years of service, or a factor of 1.33 if the original fatigue calculation assumed 60 years of service. The ISCO was analyzed for 1000 cycles of full power operation. Given maximum 80-year projections of 286 heatup/cooldowns and 34 ISCO operations, 1000 cycles are bounding for 80 years of operation, and no scaling is needed for the ISCO.

Since CUF is the ratio of the number of assumed occurrences (n) divided by the number of allowable occurrences (N), multiplying the 40-year CUF value by a factor of 2.0 effectively increases the number of assumed occurrences by a factor of 100% and multiplying the 60-year CUF value by a factor of 1.33 effectively increases the number of assumed occurrences by 33%. Therefore, screening 80-year CUFen values have an inherent margin of at least 33% more than what is projected in SLRA Table 4.3.1-1 and 4.3.1-2.

Therefore, the screening 80-year CUFen values used in the EAF screening evaluation are more conservative than the projected 80-year CUFen values calculated in the detailed EAF calculation.

(3) Transient Temperature For the detailed evaluation individual Fen values for each specified transient based on the reactor cycle diagram was used.

In contrast, for the EAF screening evaluation the calculation of the "screening 80-year CUFen" values assumed "bounding screening Fen" values which are based on the maximum specified transient temperature from the entire reactor cycle diagram for a specific thermal zone. This is conservative since Fen multipliers increase exponentially with temperature.

In addition, the ASME Section III and NUREG/CR-6909, Revision 1 methodology allows for the pairing of transients into load pairs, to calculate usage values and also allows for the calculation of transient specific CUFen values for each transient or load pair, based on the number of specified transient occurrences for the individual transient and a Fen value corresponding to the specified temperature profile for each transient. Then all the calculated CUFen values for each transient are added together into a total CUFen value for the component. This methodology allows for finer granularity in calculating a total CUFen.

This difference is best explained by an example, as follows:

The EAF screening evaluation concluded that the Unit 3 Recirc Inlet Nozzle (SS)"

component (which is in RPV region B thermal zone) was assessed a bounding screening Fen value of 9.1 based on the maximum temperature of 563°F from the reactor cycle diagram RPV region B thermal zone. This resulted in a "screening 80-year CUFen value of 1.7.

April 10, 2025 Enclosure A Page 8 of 23 The detailed evaluation refined the specified transients into 4 load pairs with each load pair assuming different average temperatures (ranging from 371 to 485°F) based on the original specified transient profile. Based on the specified temperatures, individual Fen values were calculated for each of the four load pairs. Based on these individual Fen values, four different CUFen values were calculated for each load pair and the total of the four CUFen values is concluded as the final CUFen value for the component (0.288 for Unit 2 and 0.255 for Unit 3). The calculated average Fen value of the four load pairs is 3.0 which is significantly less than the bounding screening Fen value of 9.1. This refined Fen value is more accurate based on the methodology in NUREG/CR-6909, Revision 1.

Therefore, the contribution due to the assumed maximum temperature in the EAF screening evaluation is more conservative than the contribution of the transient specific temperature profiles for each transient used on the detailed evaluation.

April 10, 2025 Enclosure A Page 9 of 23 RAI 4.3.3-2 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of 0extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.

=

Background===

SLRA Table 4.3.1-3 describes the limiting EAF locations and their CUFen values.

Issue SLRA Table 4.3.1-3 does not clearly describe the thermal zones evaluated in the EAF analysis and specific materials of fabrication associated with the limiting EAF locations. In addition, the SLRA does not clearly discuss whether a thermal zone may be bounded by another thermal zone in the EAF analysis so that a limiting location may not be identified for a thermal zone.

Request

1. Clarify the thermal zones and materials of fabrication associated with the limiting EAF locations described in SLRA Table 4.3.1-3.
2. Clarify whether a thermal zone is bounded by another thermal zone in the EAF analysis so that a limiting location may not be identified for a thermal zone. If so, describe how the applicant determined that a thermal zone is bounded by another thermal zone.

Constellation Response to Request 1:

The table below documents the thermal zones and materials of fabrication associated with the limiting EAF locations described in SLRA Table 4.3.1-3. Locations on SLRA Table 4.3.1-3 which are not wetted by reactor coolant are not listed.

April 10, 2025 Enclosure A Page 10 of 23 Material and Thermal Zones for Locations Documented on SLRA Table 4.3.1-3 No.

Location on SLRA Table 4.3.1-3 Material Thermal Zone 1

Feedwater Nozzle A Corner (FW LPA BR)

LAS Region A 2

Feedwater Nozzle A Safe End (FW LPA SE) CS FW safe end and nearby piping 3

Feedwater Nozzle B Corner (FW LPB BR)

LAS Region A 4

Feedwater Nozzle B Safe End (FW LPB SE) CS FW safe end and nearby piping 8

Isolation Condenser Straight Tube Section (ISCO_TUBE)

SS Isolation Condenser Tube Side 9

Isolation Condenser Tubesheet-Tube Junction (ISCO_TS_TUBE_JUN)

SS Isolation Condenser Tube Side 10 Isolation condenser channel nozzles (ISCO_CHAN_NOZ)

LAS Isolation Condenser Tube Side 11 Core Spray Piping Point 23 (PIPE_CSA_23) SS Core Spray Safe End and Nearby Piping 12 Core Spray Piping Flued Head (PIPE_CSA_FH)

SS Core Spray Piping, Far 14 Feedwater piping point 15A (PIPE_FWATEE)

CS FW Piping, Far 15 Main Steam Piping Point 45 (PIPE_MSBELBOW)

CS Region A 16 Recirc Piping Point A5 (PIPE_RECIRC_A5) SS Region B 17 Recirc Piping point S2 (PIPE_RECIRC_S2)

SS Region B 18 RWCU Piping Point 65 (PIPE_RWCU)

SS Region B 19 RPV Core Spray Nozzle (RPV_CSNOZ)

LAS Region B 20 Core Spray Safe End (RPV_CS_SE)

SS Core Spray Safe End and Nearby Piping 21 RPV Recirc Inlet Nozzle (RPV_INLTNOZ)

SS Region B 22 RPV Recirc Outlet Nozzle (RPV_OUTNOZ)

LAS Region B 23 RPV Shell (RPV_SHELL)

LAS Region B 24 RPV Shroud Support (RPV_SHRDSUP)

CS Region B 25 2 Instrumentation Nozzle (RPV_INST_NOZ)

NBA Region A 26 RPV Closure Flange (RPV_FLANGE)

LAS Region A 27a Pipe SRVDL A (PIPE_SRV_DL_A)

CS SRVDL, Far 27b Pipe SRVDL B (PIPE_SRV_DL_B)

CS SRVDL, Far 27c Pipe SRVDL C (PIPE_SRV_DL_C)

CS SRVDL, Far 27d Pipe SRVDL D (PIPE_SRV_DL_D)

CS SRVDL, Far 27e Pipe SRVDL E (PIPE_SRV_DL_E)

CS SRVDL, Far Notes LAS - Low Alloy Steel CS - Carbon Steel SS - Stainless Steel NBA - Inconel

April 10, 2025 Enclosure A Page 11 of 23 During development of the response to this RAI, a typographical error was identified in line item 4 of SLRA Table 4.3.1-3 (i.e., Feedwater Nozzle A should be Feedwater Nozzle B). This will be corrected in Enclosure B.

Constellation Response to Request 2:

The methodology described in SLRA Section 4.3.3 does not allow for one thermal zone to bound and represent another thermal zone.

As a result, each screened in location bounds (for fatigue) screened out locations with the same material within the associated thermal zone. All screened out components within a thermal zone are represented by a least one screened in component of the same material type.

April 10, 2025 Enclosure A Page 12 of 23 RAI 4.3.4-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.

=

Background===

SLRA Section 4.3.4 addresses the fatigue waiver TLAAs for ASME Code Section III, Class 1 components (e.g., reactor pressure vessel steam outlet nozzle and vent nozzle). Specifically, SLRA Table 4.3.4-2 discussed the number of transient cycles evaluated in the fatigue waiver reanalysis for 80 years of operation for each of the ASME Code Section III, N-415.1 criteria for fatigue waiver (i.e., N-415.1(a) through (f)).

Issue SLRA Table 4.3.4-2 does not clearly describe the 80-year projected cycles in comparison with the cycles evaluated in the 80-year fatigue waiver reanalysis.

In addition, SLRA Table 4.3.4-2 does not describe the following information on the N-415.1(f) criterion regarding significant mechanical load fluctuations: (1) transients evaluated in the fatigue waiver reanalysis, (2) transient cycles evaluated in the existing fatigue waiver analysis, (3) transient cycles evaluated in the fatigue waiver reanalysis, (4) 80-year projected cycles of the transients and (5) whether the fatigue waiver criterion is met in the fatigue waiver reanalysis.

Request

1. Describe the 80-year projected cycles in comparison with the cycles evaluated in the 80-year fatigue waiver reanalysis to confirm that the transient cycles evaluated in the fatigue waiver reanalysis are bounding for the 80-year projected cycles.
2. Describe the following information on the N-415.1(f) criterion regarding significant mechanical load fluctuations: (1) transients evaluated in the fatigue waiver reanalysis, (2) transient cycles evaluated in the existing fatigue waiver analysis, (3) transient cycles evaluated in the fatigue waiver reanalysis, (4) the 80-year projected cycles of the transients to confirm that the transient cycles evaluated in the fatigue waiver reanalysis are bounding for the 80-year projected cycles and (5) whether the fatigue waiver criterion is met in the fatigue waiver reanalysis.

April 10, 2025 Enclosure A Page 13 of 23 Constellation Response to Request 1:

Table 1 below provides a comparison between the transient occurrences assumed in the 80-year waiver reanalysis taken from SLRA Table 4.3.4-2 and the 80-year projected occurrences from SLRA Tables 4.3.1-1 and 4.3.1-2.

The transient occurrences assumed in the fatigue waiver reanalysis are greater than or equal to the 80-year projected occurrences on SLRA Tables 4.3.1-1 and 4.3.1-2. Therefore, the transient occurrences assumed in the fatigue waiver reanalysis described in SLRA section 4.3.4 are bounding for 80 years.

Constellation Response to Request 2, which includes five questions:

Response to Question 1 and 2:

The original fatigue waiver calculation Stress Analysis of Miscellaneous Nozzles addressed ASME Section III, 1963 Edition, including Summer 1964 Addenda, criterion N-415.1(f) for all the nozzles evaluated in SLRA Section 4.3.4. Except for the Steam Outlet Nozzles and the Isolation Condenser Nozzles, the calculated significant load fluctuation alternating stress range values for the remaining nozzles addressed in SLRA Section 4.3.4 did not exceed the Sa threshold associated with 1E+6 cycles. Therefore, per the guidance N-415.1(f), zero significant mechanical fluctuations were evaluated for these nozzles.

For the Steam Outlet Nozzles and the Isolation Condenser Nozzles the original fatigue waiver calculation assumed a total of 400 significant mechanical load fluctuations. The associated transients were Heatup, Cooldown, and SRV Blowdown; Loss of Feedwater; and Scram, and the total number of specified occurrences (400) are consistent with the occurrences specified on the original thermal cycle diagram.

In the fatigue waiver reanalysis, the calculated significant load fluctuation alternating stress range values for each nozzle did not exceed the Sa threshold associated with 1E+6 cycles, except for the Steam Outlet Nozzles and the Isolation Condenser Nozzles. The Steam Outlet Nozzles and the Isolation Condenser Nozzles fatigue waiver reanalysis for 80 years for criteria N-415.1(f) considered the same transients that were considered in the original fatigue waiver.

These were Heatup, Cooldown, and SRV Blowdown; Loss of Feedwater; and Scram.

Response to Question 3:

The number of transient occurrences assumed in the fatigue waiver reanalysis was 298 Heatup, Cooldown, and SRV blowdown occurrences; 80 Loss of Feedwater occurrences; and 294 Scram occurrences for a total of 672 occurrences. With these assumed occurrences for 80 years, the 80-year fatigue waiver reanalysis concluded that criterion N-415.1(f) was met for the Steam Outlet Nozzles and the Isolation Condenser Nozzles.

April 10, 2025 Enclosure A Page 14 of 23 Response to Question 4:

For Unit 2, the 80-year projection from SLRA Table 4.3.1-1 are 283/275 Heatup/Cooldowns and 4 SRV Blowdowns, 10 Loss of Feedwater, and 227 Scrams for a maximum total of 524. For Unit 3, the 80-year projections from SLRA Table 4.3.1-2 are 262/248 Heatup/Cooldowns and 1 SRV Blowdown, 8 Loss of Feedwater, and 197 Scrams for a maximum total of 468. As such, the transient occurrences evaluated in the fatigue waiver reanalysis (i.e., 672) are bounding for the 80-year projected occurrences (i.e., 524 for Unit 2 and 468 for Unit 3).

Response to Question 5:

Based on the above responses to questions 1, 2, 3, and 4; criterion N-415.1(f) is met in the fatigue waiver reanalysis.

April 10, 2025 Enclosure A Page 15 of 23 Table 1 - Comparison of Transient Occurrences Assumed In SLRA Table 4.3.4-2 to SLRA Tables 4.3.1-1 and 4.3.1-2.

Criteria Applicable Nozzles Transients Assumed in the Original Waiver and Transient Number from SLRA Tables 4.3.1-1 and 4.3.1-2.

Number of Occurrences Assumed in the Waiver Reanalysis Unit 2 80-Year Projected Number of Transients for Event Grouping from Table 4.3.1-1 Unit 3 80-Year Projected Number of Transients for Event Grouping from Table 4.3.1-2 (N-415-1(a))

Atmospheric to Operating Conditions and Back Transients All Nozzles

  • Maximum of (3) Heatup or (20)

Cooldown (11) or SRV Blowdown

  • (17) Code Hydrotest 431 333 315 (N-415-1(b))

Significant Pressure Fluctuation Transients All Nozzles * (9) Loss of Feedwater Flow

  • (11) SRV Blowdown
  • (17) Overpressure to 1375 psig 380 242 207 (N-415-1(c))

Startup and Shutdown Transients All Nozzles

  • Maximum of (3) Heatup or (20)

Cooldown (11) or SRV Blowdown 298 283 262 (N-415-1(d))

Significant Temperature Fluctuation Transients All nozzles

  • (17) Overpressure to 1375 psig 375 238 206

April 10, 2025 Enclosure A Page 16 of 23 Table 1 - Comparison of Transient Occurrences Assumed In SLRA Table 4.3.4-2 to SLRA Tables 4.3.1-1 and 4.3.1-2.

Criteria Applicable Nozzles Transients Assumed in the Original Waiver and Transient Number from SLRA Tables 4.3.1-1 and 4.3.1-2.

Number of Occurrences Assumed in the Waiver Reanalysis Unit 2 80-Year Projected Number of Transients for Event Grouping from Table 4.3.1-1 Unit 3 80-Year Projected Number of Transients for Event Grouping from Table 4.3.1-2 (N-415-1(e))

Significant Temperature Fluctuations at Dissimilar Material Discontinuities All nozzles except Steam Outlet Nozzle For the original evaluation (9) Loss of Feedwater Flow (10) Scram (11) SRV Blowdown (17) Over Pressure to 1375 psig 1 for (17)

Over for Pressure to 1375 psig (Note 1) 1 1

Steam Outlet Nozzle No Transients exceeded the significance threshold.

0 0

0 Note 1 - With respect to the criterion N-415.1(e), Significant Temperature Fluctuations at Dissimilar Material Discontinuities the 80-year reanalysis concluded that only one transient (Over Pressure to 1375 psig) exceeds the significant temperature fluctuation threshold of 152.4°F or 150.4°F for all nozzles, except the Steam Outlet Nozzle. This transient is conservatively assumed to occur one time prior to the end of the SPEO. The original evaluation calculated a significant temperature fluctuation threshold of 118.5°F. This reduced threshold resulted in the consideration of 282 occurrences of the following transients: Loss of Feedwater, Scram, Over Pressure to 1375 psig, and SRV Blowdown, for criterion N-415.1(e). The originally calculated significant temperature fluctuation threshold of 118.5 °F was due to a conservative error in the original analyses and was corrected in the re-evaluation.

April 10, 2025 Enclosure A Page 17 of 23 RAI 4.3.5-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.

=

Background===

SLRA Section 4.3.5 addresses the fatigue TLAAs for the non-Class 1 piping systems (i.e.,

ASME Section III Class 2 and 3 and ANSI B31.1 piping systems). The TLAAs are also related to the allowable stress and high energy line break (HELB) analyses for the piping systems. The TLAAs regarding allowable stress analyses rely on the implicit fatigue analysis provisions in the ASME Code Section III and ANSI B31.1 code. These provisions allow no reduction in the allowable stress range for thermal expansion stresses below 1.0, if the number of equivalent full temperature cycles does not exceed 7000 cycles.

Issue SLRA Table 4.3.5-2 describes the conservative 80-year projected cycles for the non-Class 1 piping systems that are affected by the transients other than the reactor coolant system (RCS) transients in SLRA Tables 4.3.1-1 and 4.3.1-2. However, SLRA Section 4.3.5 does not clearly describe how the 80-year projected cycles were determined (e.g., based on piping system design information, plant operation procedures, test requirements, UFSAR information and specific system-level knowledge).

Request Discuss how the applicant determined the 80-year projected cycles listed in SLRA Table 4.3.5-2 (e.g., based on piping system design information, plant operation procedures, test requirements, UFSAR information and specific system-level knowledge).

Constellation Response:

The projected cycles on SLRA Table 4.3.5-2 were developed utilizing the following information.

Conservative estimates based on the Dresden surveillance frequency control program, schedules of surveillances and inspections from the station work management database, or frequencies by the station Technical Specifications.

o For example, one of the projections for the Containment Atmosphere Monitor -

Heat Traced Tubing line item on Table 4.3.5-2 used the station Technical Specifications Requirement sections 3.3.b.1 and 3.3.b.2 which requires calibration every 92 days.

April 10, 2025 Enclosure A Page 18 of 23 Conservative estimates based on system maintenance.

o For example, one of the projections for the Reactor Water Cleanup Piping line item on Table 4.3.5-2 conservatively estimates that the system pumps are taken out of service for maintenance once per year. This is considered very conservative based on review of the systems maintenance history.

Conservative estimates based on system operational procedures.

o For example, one of the projections for the Fire Protection - Diesel Engine Exhaust line item on Table 4.3.5-2 conservatively estimates that the system will be flushed twice every 12 months based on plant procedures and the Plant Technical Requirements Manual specified surveillance frequencies.

Conservative estimates based on heating and cooling seasons.

o For example, one of the projections for the Non-Safety Related Ventilation line item on Table 4.3.5-2 conservatively estimates that the system will be placed in and out of service 20 times each heating season.

UFSAR operational requirements for the system.

o For example, one of the projections for the Isolation Condenser System Piping line item on Table 4.3.5-2 conservatively estimates one design heat removal test every year while UFSAR Section 5.4.6.4 states that the test occurs once every 10 years.

Projections in SLRA Table 4.3.1-1 and 4.3.1-2.

o For example, the Reactor Water Cleanup Piping line item on Table 4.3.5-2 uses the Plant Heat Up and Plant Cooldown projections on SLRA Tables 4.3.1-1 and 4.3.1-2.

Assessment of the system design information, UFSAR information, and operating experience indicated that extensive pre-operational testing (e.g., more than 25 occurrences) at operating system temperatures was not required for the systems addressed by the following line items from SLRA Table 4.3.5-2:

o Containment Atmosphere - Heat Traced Tubing; o Containment Atmosphere Sample Line; o Core Spray System Piping; o HPCI System Piping; o LPCI System Piping; o Non-Safety Related Ventilation; o Reactor Recirculating Piping Sample Line; o Shutdown Cooling System; and o Shutdown Cooling Sample Line.

April 10, 2025 Enclosure A Page 19 of 23 The projections for these piping segments did not consider pre-operational testing. The basis for the 25 occurrence threshold is that this value is significantly less than 7000 occurrences (i.e.,

more than two orders of magnitude).

However, in some cases, system design information and operating experience indicated that pre-operational testing was performed prior to initial plant startup. In these cases, very conservative estimates were assigned. For example:

o The Control Rod Drive System piping line item assumed 100 pre-operational testing transients for each CRD prior to initial startup, o The Fire Diesel Engines line item assumed 100 engine startup transients for each engine prior to initial startup, and o Line items with complicated control schemes, such as the Reactor Water Cleanup Piping and the Standby Gas Treatment System assumed 50 startup transients prior to initial startup.

April 10, 2025 Enclosure A Page 20 of 23 Responses to NRC Request for Confirmation of Information Set 1 as follows:

RCI B.2.1.28-1 SLRA Table 3.3.2-15, Plant Specific Note 1, and SLRA Table 3.4.2-5, Plant Specific Note 1 states that the components noted (drywell equipment drain sump heat exchangers, reactor building equipment drain tank heat exchangers, and turbine oil reservoirs) meet the six criteria in GALL-SLR AMP XI.M42, element 4, to use the Inspection of Internal Surfaces in Miscellaneous Piping and Ducting Components (SLRA B.2.1.24) program in lieu of the Internal Coatings/Linings for In-Scope Piping, Piping Components, Heat Exchangers, and Tanks (SLRA B.2.1.28) program.

During the audit, the staff observed that the program basis document for this AMP stated that for the drywell equipment drain sump heat exchangers and the reactor building equipment drain tank heat exchangers there are no downstream components credited with performing 10 CFR 54.4 (a)(1), (a)(2), or (a)(3) functions that are susceptible to flow blockage from potential coating debris. The staff also observed that the program basis document stated that for the turbine oil reservoirs the tank pumps have screens and filters to remove particulate, and there is instrumentation that can monitor filter differential pressure (indicating a clogged filter).

Confirm that the above specified components meet the first criterion in GALL-SLR AMP XI.M42, element 4 which states:

Loss of coating or lining integrity cannot result in downstream effects such as reduction in flow, drop in pressure, or reduction of heat transfer for in-scope components.

Constellation Response:

CEG confirms that the information provided above is correct.

April 10, 2025 Enclosure A Page 21 of 23 RCI B.2.1.28-2 During the audit, the staff observed that the program basis document stated that for the drywell equipment drain sump heat exchangers and the reactor building equipment drain tank heat exchangers the waste water environment does not contain aggressive chemicals that could cause accelerated corrosion of these components. The staff also observed that the program basis document stated that for the turbine oil reservoirs the lubricating oil environment is not aggressive and would not be expected to result in any significant corrosion of this component.

Confirm that the above specified components meet the third criterion in GALL-SLR AMP XI.M42, element 4 which states:

The internal environment does not contain chemical compounds that could cause accelerated corrosion of the base material if coating/lining degradation resulted in exposure of the base metal.

Constellation Response:

CEG confirms that the information provided above is correct.

RCI B.2.1.28-3 During the audit, the staff observed that the program basis document stated that for the drywell equipment drain sump heat exchangers and the reactor building equipment drain tank heat exchangers the waste water environment does not promote microbiologically induced corrosion (MIC) of these components, and that an operating experience review has not identified any significant MIC issues in these systems. The staff also observed that the program basis document stated that for the turbine oil reservoirs the lubricating oil environment does not promote MIC of the base metal.

Confirm that the above specified components meet the fourth criterion in GALL-SLR AMP XI.M42, element 4 which states:

The internal environment would not promote microbiologically influenced corrosion of the base metal.

Constellation Response:

CEG confirms that the information provided above is correct.

April 10, 2025 Enclosure A Page 22 of 23 RCI B.2.1.28-4 During the audit, the staff observed that the program basis document stated that for the drywell equipment drain sump heat exchangers and the reactor building equipment drain tank heat exchangers there are no uncoated components in the vicinity that could cause galvanic corrosion. The staff notes that, although the program basis document does not address the presence or absence of uncoated components in the vicinity of the turbine oil reservoirs, the absence of an aqueous internal environment in the turbine oil reservoirs makes galvanic corrosion extremely unlikely during normal operating conditions.

Confirm that the above specified components meet the fifth criterion in GALL-SLR AMP XI.M42, element 4 which states:

The coated/lined components are not located in the vicinity of uncoated components that could cause a galvanic couple to exist.

Constellation Response:

CEG confirms that the information provided above is correct.

RCI B.2.1.28-5 During the audit, the staff was unable to independently verify that the above specified components meet the sixth criterion in GALL-SLR AMP XI.M42, element 4 which states that the design for the component did not credit the coating/lining (e.g., the corrosion allowance was not zero).

Confirm that the above specified components meet the sixth criterion in GALL-SLR AMP XI.M42, element 4 which states:

The design for the component did not credit the coating/lining (e.g., the corrosion allowance was not zero).

Constellation Response:

CEG confirms that the components specified in RCI B.2.1.28-1 meet the sixth criterion in GALL-SLR AMP XI.M42, element 4, as stated above.

April 10, 2025 Enclosure A Page 23 of 23 Responses to NRC Request for Confirmation of Information Set 2 as follows:

RCI 3.3.2-1 Please confirm that the raw water environment for the polyurethane based cured-in-place polymer-pipe liner in the Fire Protection System does not contain aggressive chemicals that may cause cracking or blistering. In addition, please confirm that there is no plant-specific operating experience for the polyurethane based cured-in-place-polymer-pipe liner exposed internally to raw water in the Fire Protection System due to age-related degradation.

Constellation Response:

CEG confirms that the information provided above is correct.

RCI B.2.1.27-1 Based on discussions between the applicant and staff during the audit, it is the staffs understanding that carbon fiber reinforced polymer (CFRP) piping and piping components in the condensate system (SLRA Table 3.4.2-1) is referring to a CFRP wrap applied over existing piping, such that the internal surface of the wrap is not in direct contact with the treated water environment but is in direct contact with the soil environment. Confirm that this is an accurate assessment.

Constellation Response:

CEG confirms that the information provided above is correct. For clarification, the external surface of the wrap is in direct contact with the soil environment.

RCI B.2.1.11

1. Based on discussions between the applicant and staff during the audit, it is the staffs understanding that CFRP piping and piping components in the open cycle cooling water system are referring to a CFRP wrap applied over existing piping, such that the internal surface of the wrap is not in direct contact with the raw water environment and therefore, flow in these lines does not affect the intended function of spatial interaction. Confirm that this is an accurate assessment.
2. Based on discussions between the applicant and the staff during the audit, it is the staffs understanding that CFRP piping in the open cycle cooling water system underwent chemical resistance testing (i.e., pickle jar test) to ensure the CFRP was appropriate for use due to exposure to ultraviolet light, ozone, radiation, or chemical attack and therefore, cracking or blistering are not applicable aging mechanisms. Confirm that this is an accurate statement.

Constellation Response:

CEG confirms that the information provided above is correct.

Retrieved from "https://kanterella.com/w/index.php?title=ML25100A134&oldid=5467910"