ML24325A593

LLC, Response to NRC Request for Additional Information No. 036 (RAI-10350 R1) on the NuScale Standard Design Approval Application

ML24325A593
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Site:	05200050, 99902078
Issue date:	11/20/2024
From:	Shaver M NuScale
To:	Office of Nuclear Reactor Regulation, Document Control Desk
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RAIO-175965
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RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com November 20, 2024 Docket No.52-050 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Response to NRC Request for Additional Information No. 036 (RAI-10350 R1) on the NuScale Standard Design Approval Application

REFERENCE:

NRC Letter to NuScale, Request for Additional Information No. 036 (RAI-10350 R1), dated September 19, 2024 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) response to the referenced NRC Request for Additional Information (RAI).

The enclosures to this letter contain NuScale's responses to the following RAI questions from NRC RAI-10350 R1:

6.3-7 6.3-9 6.3-10 6.3-11 Enclosures 2, 4, and 6 are the proprietary versions of the NuScale Response to NRC RAI No. 036 (RAI-10350 R1, Questions 6.3-9, 6.3-10, and 6.3-11). NuScale requests that the proprietary version be withheld from public disclosure in accordance with the requirements of 10 CFR § 2.390. The enclosed affidavit (Enclosure 8) supports this request. Enclosures 2, 4, and 6 have also been determined to contain Export Controlled Information. This information must be protected from disclosure per the requirement of 10 CFR § 810. Enclosures 1, 3, 5, and 7 are the nonproprietary versions of the NuScale response.

This letter makes no regulatory commitments and no revisions to any existing regulatory commitments.

RAIO-175965 Page 2 of 2 11/20/2024 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com If you have any questions, please contact Jim Osborn at 541-360-0693 or at josborn@nuscalepower.com.

I declare under penalty of perjury that the foregoing is true and correct. Executed on November 20, 2024.

Sincerely, Mark W. Shaver Director, Regulatory Affairs NuScale Power, LLC Distribution:

Mahmoud Jardaneh, Chief New Reactor Licensing Branch, NRC Getachew Tesfaye, Senior Project Manager, NRC

NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-7, Nonproprietary : NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-9, Proprietary : NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-9, Nonproprietary : NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-10, Proprietary : NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-10, Nonproprietary : NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-11, Proprietary : NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-11, Nonproprietary : Affidavit of Mark W. Shaver, AF-175966

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-7, Nonproprietary

Response to Request for Additional Information Docket: 052000050 RAI No.: 10350 Date of RAI Issue: 09/19/2024 NRC Question No.: 6.3-7 Issue Description The NPM-20 SDA design relies on the key design aspects of the ECCS supplemental boron (ESB) feature to provide the appropriate long-term cooling response to AOOs and other design basis events. The integrated functionality of an NPM-20 ESB has not been tested and demonstrated. Performance of the full scale as-built ESB can be impacted by the geometry and functional arrangement of key components, variations in as-built parameters, and uncertainties associated with complex thermal-hydraulic phenomena, especially when considering the integrated system.

During an audit NuScale stated that proper ESB function is assured by boron dissolution separate effects testing; technical specification operability requirements; existing inspections, tests, analyses, and acceptance criteria (ITAAC); and conservatisms applied within the evaluation of ESB performance. The staff views these elements, and other system information provided in the FSAR, as pertinent to the establishment of performance requirements for the system and necessary to perform the safety analysis of the design, all of which are necessary to support a final safety determination of the standard design. However, this does not satisfy the additional requirements of an initial test program which are intended to provide assurance that the system operates in accordance with the design; validate, to the extent practical, the analytical models; and verify the correctness or conservatism of assumptions used to predict plant responses to anticipated transients and postulated accidents.

The ESB is a first-of-a-kind (FOAK) engineered safety feature. FOAK tests are used for new, unique, or special tests to verify design features reviewed by the NRC and set into operation for the first time. Integrated functional testing of the constructed ESB would provide assurance that the as-built system response conforms to the analytical predictions as noted above.

NuScale Nonproprietary NuScale Nonproprietary

Information Requested The applicant is requested to modify an existing initial test program or ITAAC test, or develop a new test, to demonstrate acceptable performance of the as-built ESB based on predicted system response under expected test conditions to ensure the system as a whole meets fundamental design requirements of the safety analysis. The test should confirm the as-built functionality of the ESB, including boron basket dissolution rates, condensate rail collection capability, mixing tube flow, lower containment boron concentration and mixing, and hopper loading sensor functionality.

The staff observes that such a test may only be needed for the first module, given its purpose to confirm the performance of a first-of-a-kind safety system and verify the conservatism in the safety analyses. In addition, as noted above, appropriate data gathering could be integrated into a test that is already planned to assess plant transient response.

NuScale Response:

Final Safety Analysis Report Section 14.2 is revised to include the ECCS supplemental boron feature to the existing first of a kind test for the emergency core cooling system, Test 40.02.01 (Table 14.2-40).

Response to NRC Feedback Provided October 22, 2024 On October 22nd, the staff provided the following feedback to NuScales initial response to request for additional information 6.3-7:

The acceptance criteria for the new ESB tests state the ESB boron dissolution and coolant boron concentration is within the bounds established for the test, accounting for test conditions and uncertainty. The staff expects the test acceptance criteria to be developed using the analysis methods and code of record based on predictions of the as-tested conditions. Please update the response to explain the phrase within the bounds established for the test, accounting for test conditions and uncertainty and confirm this will be determined based on predications using the methods documented in FSAR Chapter 15 and associated topical report(s).

NuScale Nonproprietary NuScale Nonproprietary

The code of record is used to the extent practical to confirm the performance of ECCS supplemental boron. However, code modifications may be necessary to reflect unique flow paths present for the test conditions.

Impact on US460 SDAA:

FSAR Section 14.2 has been revised as described in the response above and as shown in the markup provided in this response.

NuScale Nonproprietary NuScale Nonproprietary

NuScale Final Safety Analysis Report Initial Plant Test Program NuScale US460 SDAA 14.2-10 Draft Revision 2 automatic operation of tank or basin level control valve local grab sample can be obtained from a system grab sample device automatic bus transfer via bus tie breaker system instrument calibration each instrument can be monitored in the MCR (test not required if the instrument calibration verified the MCR display) 14.2.3.3 Testing of First-of-a-Kind Design Features First-of-a-kind (FOAK) tests are new, unique, or special tests to verify design features reviewed for the first time by the NRC. The NuScale Power Plant contains design features that are new and unique and not tested previously; therefore, testing of these design features is treated as FOAK. For the FOAK tests, the testing frequency is specified in the test abstract. The Comprehensive Vibration Assessment Program (CVAP) is an FOAK program. The program is implemented consistent with the requirements of the NuScale Comprehensive Vibration Assessment Program Technical Report," TR-121353-P, and the NuScale Comprehensive Vibration Assessment Program Measurement and Inspection Plan Technical Report, TR-121354-P. The CVAP is addressed in Section 3.9.2.

Audit Question A-3.9.2-31 The following ITP test abstracts describe the on-site CVAP testing of FOAK design features:

Audit Question A-3.9.2-31 Table 14.2-65: Steam Generator Flow-Induced Vibration Test #65, that is performed at an offsite test facility and occurs outside the scope of preoperational testing and startup testing Audit Question A-3.9.2-31 Table 14.2-102: NuScale Power Module Vibration Test #102, that is performed during startup testing The test results for the CVAP testing of the first NPM inform the required CVAP testing on subsequent NPMs as described in TR-121353-P. Other ITP testing of FOAK design features is performed for each NPM, except as described below.

RAI 6.3-7 Table 14.2-40: Emergency Core Cooling System Test #40 includes a one-time in-situ system performance test of the emergency core cooling system (ECCS).

The test demonstrates ECCS valve response, containment response, and ECCS supplemental boron (ESB) responsevalve and containment response to manual emergency safety feature actuation of the ECCS at hot functional test pressure and temperature.

Section 5.4.3 contains a description of the decay heat removal system (DHRS) one-time in-situ RCS heat removal test. The test is performed per test abstract Table 14.2-41: Decay Heat Removal System Test # 41.

NuScale Final Safety Analysis Report Initial Plant Test Program NuScale US460 SDAA 14.2-97 Draft Revision 2 Audit Question A-14.2-1 RAI 6.3-7 Table 14.2-40: Test # 40 Emergency Core Cooling System Preoperational test is required to be performed for each NPM.

System Level Test 40.02.01 is only required to be performed once for the first NPM tested. This test supports FOAK testing as described in Section 14.2.3.3.

The ECCS is described in Section 6.3, and the functions verified by this test are:

System Function System Function Categorization Function Verified by Test #

1. The ECCS supports the RCS by opening the ECCS reactor vent valves (RVVs) and reactor recirculation valves (RRVs) when their respective trip valve is actuated by the MPS.

safety-related 40.02.01 56.02.02

2. The ECCS supports the RCS by providing recirculated coolant from the containment to the RPV for the removal of core heat.

safety-related 40.02.01 56.02.02

3. The ESB feature supports the ECCS by providing boron to recirculated coolant during ECCS operation.

safety-related 40.02.01 The ECCS functions verified by other tests are:

System Function System Function Categorization Function Verified by Test #

3. The ECCS supports the RCS by providing LTOP for maintaining the reactor coolant pressure boundary.

safety-related 56.02.02

4. The ECCS supports the CNTS by providing a portion of the containment boundary for maintaining containment integrity.

safety-related 38.02.01

5. The ECCS supports MPS by providing PAM instrument information signals.

nonsafety related 59.02.01 40.00.XX Prerequisites

01. Verify an instrument calibration is completed, with approved records and within calibration due dates, for instruments required to perform this test.

40.01.XX Component Level Tests Test Objective Test Method Acceptance Criteria None01.Verify each ECCS instrument is available on an MCS or PCS display. (Test not required if the instrument calibration verified the MCS or PCS display.)

1) Initiate a single real or simulated instrument signal from each ECCS transmitter.

1) The instrument signal is displayed on an MCS or PCS display, or is recorded by the applicable control system historian.

NuScale Final Safety Analysis Report Initial Plant Test Program NuScale US460 SDAA 14.2-98 Draft Revision 2 40.02.XX System Level Test 40.02.01.

Test 40.02.01 is performed at hot functional testing to allow ECCS actuation at elevated RCS pressure and temperature conditions, starting just above the inadvertent actuation block (IAB).

The RCS is heated to the highest temperature achievable by MHS heating. These hot functional testing conditions provide the highest temperature conditions that can be achieved before fuel load.Ensure RCS pressure is above the IAB pressure threshold. Use MHS heating to establish the highest RCS temperature allowable for the RCS test pressure. The RCS level is within the expected range of module operation, near the low end of the normal operating range for hot zero power (HZP) conditions. This test can be performed concurrently with Test 56.02.02.

Test Objective Test Method Acceptance Criteria

1. Verify ECCS RVVs open upon ECCS initation.

2. Verify ECCS RRVs remain closed above the IAB block threshold differential pressure setpoint.

13. Verify ECCS RRVC valves open below thehigh RCS pressure IAB release differential pressure setpoint.

24. Verify the RPV liquid level remains above the top of the core during and following ECCS actuation.

35. Verify the heat removal capacity of the ECCS, operating with the CNV, is consistent with the design basis.

6. Verify ECCS supplemental boron (ESB) pellets dissolve following ECCS actuation.

7. Verify boron concentration in the NPM following ECCS actuation.

1) Ensure RCS pressure is as close to, but above, the IAB RCS pressure threshold as practicable.

2) Ensure RCS temperature is at the maximum temperature achievable by heating the RCS using MHS heating.

3) Ensure RCS level is as low in the normal operating band as is practically achievable for the established plant conditions.

41) Manually initiate ECCS from the MCR.

52) Allow RPV riser level and CNV conditionslevel to become relatively stable.

3) Verify boron pellet dissolution through visual inspection or physical measurement.

4) Take a coolant sample at a sampling point in the NPM liquid space.

Note 3 and 4 can be performed together, or in any order.

1) ECCS RVVs open upon ECCS initiation.

2) ECCS RRVs remain closed above the IAB block threshold differential pressure setpoint.

13) ECCS RRVs open below the IAB release differential pressure setpoint.

24) RPV riser level remains above the top of the core.

35) CNV pressure remains within upper and lower bounds calculated using safety analysis methods, while accounting for test initial conditions and instrumentation uncertainty.

[ITAAC 02.01.14]

[ITAAC 02.01.19]

6. ESB boron dissolution is within the bounds established for the test, accounting for test conditions and uncertainty.

7. Coolant boron concentration at a sampling point in the NPM liquid space is within the bounds established for the test, accounting for test conditions and uncertainty.

Table 14.2-40: Test # 40 Emergency Core Cooling System (Continued)

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-9, Proprietary

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-9, Nonproprietary

Response to Request for Additional Information Docket: 052000050 RAI No.: 10350 Date of RAI Issue: 09/19/2024 NRC Question No.: 6.3-9 Issue Description FSAR Section 6.3.2.2.1 states two ESB dissolvers add boron to the ECCS recirculating coolant for reactivity control and the ESB dissolvers are fed by hoppers during the startup process.

During the audit, NuScale stated that this information was addressed as part of the staffs FSAR Chapter 16 review resulting in corresponding changes to LCO 3.5.4 and the cycle-specific core operating limits report (COLR). However, the safety analysis is based on certain non-cycle-specific key parameters and analytical limits for the ESB dissolvers. For example, the staff understands that there are maximum and minimum ranges for pellet diameter, as well as a standard pellet shape (i.e., equilateral cylinder). These are important parameters that need to be included in the FSAR.

Additionally, the FSAR does not include a description of the loading evolution prior to startup or explain how confirmation of establishing initial conditions will be accomplished. For example, FSAR Table 6.3-5 identifies the presence of dissolver basket indication; however, no other information of the loading sensors is provided in the FSAR.

Information Requested The staff requests the FSAR to be updated to provide design information sufficiently detailed for the reader to understand the system design and its relationship to the safety analysis to make the necessary finding. This information should include: 1) a description of pellet form (i.e.,

limitations on range of sizes and its shape); 2) a description of the loading/reloading process, including the plant conditions assumed during this evolution; 3) how proper quantity of boron pellets added to the hopper is determined; and 4) a description of instrumentation and sensors utilized by plant personnel to confirm proper remote transport of the boron pellets from the hopper to the dissolver basket.

NuScale Nonproprietary NuScale Nonproprietary

NuScale Response:

Item 1: Pellet Form The response to audit item A-15.0.5-1 provides the range of the emergency core cooling system supplemental boron feature (ESB) pellet diameter and pellet shape assumed in the boron transport analyses. This information was added to the Final Safety Analysis Report (FSAR) in response to A-15.0.5-1.

Item 2: Loading Process Each ESB dissolver has an associated loading hopper, as shown in FSAR Figure 6.3-1.

Personnel load the hopper with boron oxide pellets before plant start-up activities i.e. prior to establishing the containment pressure boundary. During module startup, the containment flooding and drain system drains the containment vessel as part of the standard NuScale Power Module start up process. Operators remotely actuate the hoppers to release the boron oxide pellets to the associated dissolvers after containment has been drained to a level below the dissolvers and the dissolvers are sufficiently dry to accept the boron oxide pellets. Dissolver loading sensors indicate that the required quantity of boron oxide has been delivered from the hoppers to the dissolvers thereby establishing the required initial conditions for ESB to perform its safety function.

Table 6.3-5 of the FSAR, Classification of Structures, Systems, and Components, includes the supplemental boron dissolver indication sensor. This element provides indication that boron pellets are in position during startup and ensures initial conditions are in place for ESB operability. The safety-related function of ESB is to provide dissolved boron to recirculated coolant from containment to ensure the core remains subcritical for design-basis events. The ESB loading instrumentation is not part of this safety-related function and is not relied upon to mitigate design-basis events. Therefore, the ESB loading instrumentation is classified as non-safety related.

NuScale revises FSAR Section 6.3 to include a paragraph about the ESB loading process.

Item 3: Verification of Boron Quantity Technical Specification Limiting Condition for Operation 3.5.4 requires the form and quantity of boron in the ESB dissolvers to be within the limits specified in the cycle-specific Core Operating Limits Report (COLR). Technical Specification Surveillance Requirement 3.5.4.1 requires the NuScale Nonproprietary NuScale Nonproprietary

form and quantity of boron to be verified prior to entering Mode 1 after operations that could have previously affected the form or quantity of boron in the ESB dissolvers (e.g., emergency core cooling system actuation).

Prior to startup, plant personnel load the hoppers with the required boron pellets in accordance with the COLR. During the startup process, once the NPM is sufficiently drained, plant personnel remotely actuate the hoppers to release boron pellets to the dissolvers using the force of gravity. The weight-based dissolver loading sensors provide indication the dissolvers are loaded.

Item 4: ESB Instrumentation The ESB loading sensors are nonsafety-related sensors that provide indication that the boron oxide pellets are initially positioned in the ESB dissolvers. The sensors are Seismic Category II weight element sensors that provide signals to the module control system. This allows operators in the main control room to verify ESB operability in accordance with Technical Specifications.

Final Safety Analysis Report Figure 6.3-1 shows the loading sensors as weight elements associated with the dissolver assemblies.

Response to NRC Feedback Provided October 22, 2024 On October 22nd, the staff provided the following feedback to NuScales initial response to request for additional information 6.3-9:

The RAI response points to audit item A-15.0.5-1 for the description of the boron oxide pellet form. The markups provided in FSAR Section 15.0.5.3 as part of the updated response to A-15.0-5-1 states the boron oxide pellets are conservatively modeled as equilateral cylinders with 3/8 in diameter. It is unclear to the staff if this information is a simplified conservativism for analytical purposes or if this is the actual design specifications for the boron oxide pellets. In addition, the staff could not find information in the FSAR related to the minimum diameter of the pellets. NuScale is requested to clearly identify the design parameters of the boron oxide pellets in the FSAR, including the range of sizes and form. As an example, this information could be included in FSAR Table 15.0-22, or within FSAR Section 6.3.

Separately, the updated response states FSAR Figure 6.3-1 shows the loading sensors as weight elements associated with the dissolver assemblies. The staff observes Figure 6.3-1 was updated as part of CP-3508 and replaces the limit switch symbols on the NuScale Nonproprietary NuScale Nonproprietary

supplemental boron dissolver assemblies with weight element symbols, designated WE. However, the staff could not find this drawing symbol or abbreviation in FSAR legends of symbols and characters (Figure 1.7-1a through Figure 1.7-3d). The staff requests NuScale to include the weight element symbol and/or instrumentation abbreviation in the appropriate FSAR symbol legend.

Feedback Item 1 In response to A-15.0.5-1, the FSAR was revised to include the analysis parameters for boron oxide pellets. Section 15.0.5.3.1 states, boron oxide pellets conservatively modeled as equilateral cylinders with 3/8 in. diameter, which is larger than the actual design diameter, for cases with slow-biased boron dissolution from the ESB. This is a maximum value for pellet diameter because it is applied to the slow-biased boron dissolution analysis, which is clarified on page two of audit response A-15.0.5-1:

((2(a),(c),ECI As stated, the slow bias uses the upper bound of the pellet diameter, while the fast bias does not require geometric inputs for the boron oxide. Therefore, the inclusion of 3/8 in. within FSAR Section 15.0 is sufficient. Section 6.3 is revised to state the pellet pellets satisfy the analysis requirements. NuScale Nonproprietary NuScale Nonproprietary

Feedback Item 2 Figure 1.7-3d includes a legend for instrumentation and letters within piping and instrumentation diagrams. As stated, the first letter is the measured variable and subsequent letters specify device functions. The table for the first letter includes W as weight/force. The table for subsequent letters includes E as a primary element. Therefore, the current legend establishes WE as a weight element. No changes to FSAR Section 1.7 are necessary. Impact on US460 SDAA: FSAR Section 6.3 has been revised as described in the response above and as shown in the markup provided in this response. NuScale Nonproprietary NuScale Nonproprietary

NuScale Final Safety Analysis Report Emergency Core Cooling System NuScale US460 SDAA 6.3-9 Draft Revision 2 This ECCS hold mode maintains energized ECCS trip valve solenoids without an actuation signal, but sheds the load at 24 hours ensuring sufficient battery power for post-accident monitoring for at least 72 hours. The ECCS immediately initiates upon receipt of an ECCS actuation signal as listed in Table 6.3-1 during the 24-hour timing period. An timer automatically actuates ECCS eight hoursactuation after an automatic or manual reactor trip to allows the ECCS supplemental boron to recirculate into the reactor core region before xenon decays from the core, to passively ensuringe subcriticality without requiring operator actions. The RCS is also maintained inert by the actuation of the eight hour ECCS timer. Section 6.2.5 describes operation of the passive autocatalytic recombiner to maintain containment inert. Operators may manually blockbypass the actuation if subcriticality at cold conditions is confirmed and if it is confirmed that sufficient hydrogen concentration will be maintained in the RCS throughout DHRS cooldown to preclude radiolytic generation of combustible gases.upon confirmation of subcriticality at cold conditions. 6.3.2.2.1 ECCS Core Cooling System Supplemental Boron Audit Question A-6.3-6 Upon actuation of ECCS, an ECCS supplemental boron (ESB) feature provides additional boron concentration to ensure that the reactor remains subcritical for at least 72 hours following an design-basis event. Thus for DBEs, tThe combined reactivity of the control rod assemblies and ESB ensures reactivity is controlled in accordance with GDC 27, as demonstrated in Section 15.0.5. Section 19.3.2, Structures, Systems, and Components Identification and Designation within Regulatory Treatment of Nonsafety Systems Program Scope, discusses subcriticality in the period beginning 72 hours after a design-basis event and lasting the following 4 days. The ESB provides sufficient boron to ensure core subcriticality and that the reactor core boron concentration remains below precipitation limits. The ESB and its components are not part of the RCPB and accordingly are not required to be designed to Quality Group A requirements. They are designed to remain operable following a design basis seismic event. RAI 6.3-9 The two ESB dissolvers add boron to the ECCS recirculating coolant for reactivity control to maintain subcriticality following some design basis events (Figure 6.3-2). The dissolvers maintain subcriticality when the highest-worth control rod is stuck in a fully withdrawn position during long term cooling to prevent an overcooling return to power. Although the boron added by the dissolvers is not necessary during all design basis events to maintain subcriticality, the dissolvers are passive and respond to design basis accidents and transients that result in ECCS actuation where condensate forms on the inner containment surfaces. The geometric form and quantity of boron added to the ESB dissolvers is within the bounds established in the Chapter 15 accident analysis, which satisfies the methodology included in the extended passive cooling EM (Reference 6.3-2). However, the specific geometric form and quantity of boron is cycle-specific and is included in the technical specifications Core Operating Limits Report.The dissolvers are fed

NuScale Final Safety Analysis Report Emergency Core Cooling System NuScale US460 SDAA 6.3-10 Draft Revision 2 by hoppers during the startup process and do not require personnel in the area to perform dissolver loading. This activity is performed remotely. Audit Question A-6.3-8 The dissolvers are located inside the CNV. The dissolvers contain solid boron oxide that is loaded during startup and remains unused during normal plant operations, without ECCS actuation. Two condensate channels (i.e., one main channel and one auxiliary channel) extend outwards and upwards from each dissolver along the CNV inner wall. The main condensate channel directs condensate to the dissolver basket for dissolution. The auxiliary channel directs water to the inside annulus space of the dissolver, providing additional condensate flow and preventing precipitation of boric acid out of solution. The dissolvers are located below the reactor pool level to ensure that sufficient condensate is generated above the channels. The condensate that is generated on the CNV wall during ECCS actuation is directed towards the dissolvers which dissolve the boron oxide creating a boric acid solution. This solution subsequently exits the dissolver and is added to the ECCS recirculating coolant in the CNV and enters the RPV through the RRVs. Two lower mixing tubes are located on the inside wall of containment below the CNV flange. These mixing tubes are designed to force condensate flow to the bottom of containment. During ECCS actuation a portion of condensate generated on the CNV inner wall is captured by condensate channels and redirected through the lower mixing tubes. This collected condensate creates a water column in the lower mixing tubes, which is used to passively mix the collected condensate with the colder or more highly borated liquid in the bottom of containment. This mixing ensures the colder and potentially higher boron concentration coolant is not sequestered below the RPV flange and is sufficiently mixed and recirculated into the core through the RRVs. RAI 6.3-9 During refueling outages, the ESB hoppers are loaded with solid boron oxide pellets. During module startup, the CNV is drained using the containment flooding and drain system. Once CNV water level is drained to a level below the boron dissolvers and the dissolvers are sufficiently dry, the hoppers are remotely actuated to release the boron oxide pellets to the associated dissolvers by the force of gravity. The dissolver loading sensors indicate that the required quantity of boron oxide has been delivered from the hoppers to the dissolvers, thereby establishing the required initial conditions for ESB to perform its safety-related function. Audit Question A-6.3.2.2.1-1 Figure 6.3-5 provides a simplified view of the ESB feature in the CNV. Table 6.3-4 provides design parameters of the ESB feature. 6.3.2.3 Applicable Codes and Classifications The pressure boundary components of the ECCS (valves, hydraulic lines, and actuator assemblies) are Quality Group A, Seismic Category I components

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-10, Proprietary

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-10, Nonproprietary

Response to Request for Additional Information Docket: 052000050 RAI No.: 10350 Date of RAI Issue: 09/19/2024 NRC Question No.: 6.3-10 Issue Description FSAR Section 6.3.2.2 states operators may manually bypass the automatic actuation of ECCS after reactor trip upon confirmation of subcriticality at cold conditions and that sufficient hydrogen concentration will be maintained in the reactor coolant system (RCS) throughout DHRS cooldown to preclude radiolytic generation of combustible gases. FSAR Chapter 7 specifies the actuation delay is 8 hours. However, it is not clear how these criteria will be determined by the control room operator and what information available in the control room will be used by the operator when determining whether it is acceptable to bypass the ECCS timer. NuScale stated in the audit that the expected operational requirements for the manual bypass of the 8-hour ECCS timer (i.e., block the ECCS actuation due to the 8-hour timer) include confirming subcriticality at cold conditions [defined as 200°F] and the detailed steps are expected to include confirmation of control rod insertion. Information Requested NuScale is requested to clarify if all cycle-specific core designs will ensure the reactor remains subcritical under cold conditions when all control rods are inserted, and if so, prescribe this in the FSAR. If not, NuScale is requested to describe the criteria and information available to the control room operators at the time of a reactor trip that will be used to objectively determine sufficient shutdown margin under cold conditions such that it is appropriate to bypass the 8-hour ECCS actuation delay. Corresponding updates to the FSAR should be provided. NuScale Nonproprietary NuScale Nonproprietary

NuScale Response: The staffs request includes the following: NuScale is requested to describe the criteria and information available to the control room operators at the time of a reactor trip that will be used to objectively determine sufficient shutdown margin under cold conditions such that it is appropriate to bypass the 8-hour ECCS actuation delay. Operators are not required to bypass the 8-hour ECCS actuation delay because, with no actions taken, the emergency core cooling system (ECCS) will actuate 8 hours following reactor trip, and the module remains in a safe condition. If operators desire to bypass the 8-hour ECCS actuation, operators must perform a reactivity balance to verify subcriticality at cold conditions (not shutdown margin). Performance of a reactivity balance is a standard practice used in the industry. Operators primarily use control rod position and boron concentration for confirmation of shutdown margin after reactor trip, and verify these parameters versus a simple graph or table that includes core life, prior to the 8-hour ECCS actuation. Operators do not need to perform the verification needed to bypass the 8-hour ECCS actuation immediately after reactor trip. The staffs request includes the following: NuScale is requested to clarify if all cycle-specific core designs will ensure the reactor remains subcritical under cold conditions when all control rods are inserted... (( eff

}}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

(( }}2(a),(c),ECI Impact on US460 SDAA: There are no impacts to US460 SDAA as a result of this response. NuScale Nonproprietary NuScale Nonproprietary

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-11, Proprietary

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com NuScale Response to NRC Request for Additional Information RAI-10350 R1, Question 6.3-11, Nonproprietary

Response to Request for Additional Information Docket: 052000050 RAI No.: 10350 Date of RAI Issue: 09/19/2024 NRC Question No.: 6.3-11

Background

By letter dated October 31, 2023, NuScale Power, LLC (NuScale or the applicant) submitted Part 2, Final Safety Analysis Report (FSAR), Chapter 6, Engineering Safety Features, Revision 1 (Agencywide Documents Access and Management System Accession No. ML23304A345), of the NuScale Standard Design Approval Application (SDAA) for its US460 standard plant design. The applicant submitted the US460 standard plant SDAA in accordance with the requirements of Title 10 Code of Federal Regulations (10 CFR) Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants, Subpart E, Standard Design Approvals. The NRC staff has reviewed the information in Chapter 6 of the SDAA, and other Chapters as necessary, and determined that additional information is required to complete its review. Regulatory Basis General Design Criterion (GDC) 1, Quality standards and records, requires that structures, systems, and components important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed. Where generally recognized codes and standards are used, they shall be identified and evaluated to determine their applicability, adequacy, and sufficiency and shall be supplemented or modified as necessary to assure a quality product in keeping with the required safety function. GDC 26, Reactivity control system redundancy and capability, requires that two independent reactivity control systems of different design principles shall be provided. One of the systems shall use control rods, preferably including a positive means for inserting the rods, and shall be capable of reliably controlling reactivity changes to assure that under conditions of normal operation, including anticipated operational occurrences, and with appropriate margin for NuScale Nonproprietary NuScale Nonproprietary

malfunctions such as stuck rods, specified acceptable fuel design limits are not exceeded. The second reactivity control system shall be capable of reliably controlling the rate of reactivity changes resulting from planned, normal power changes (including xenon burnout) to assure acceptable fuel design limits are not exceeded. One of the systems shall be capable of holding the reactor core subcritical under cold conditions. GDC 27, Combined reactivity control systems capability, requires that the reactivity control systems shall be designed to have a combined capability, in conjunction with poison addition by the emergency core cooling system, of reliably controlling reactivity changes to assure that under postulated accident conditions and with appropriate margin for stuck rods the capability to cool the core is maintained. GDC 37, Testing of emergency core cooling system, requires that the emergency core cooling system (ECCS) shall be designed to permit appropriate periodic pressure and functional testingto assure (1) the structural and leaktight integrity of its components, (2) the operability and performance of the active components of the system, and (3) the operability of the system as a whole and, under conditions as close to design as practical, the performance of the full operational sequence that brings the system into operation, including operation of applicable portions of the protection system, the transfer between normal and emergency power sources, and the operation of the associated cooling water system. 10 CFR 52.79(a)(28) requires preoperational testing and initial operations. 10 CFR 52.47(b)(1) requires applications to contain the proposed inspections, tests, analyses, and acceptance criteria (ITAAC) that are necessary and sufficient to provide reasonable assurance that, if the inspections, tests, and analyses are performed and the acceptance criteria met, a plant that incorporates the design is built and will operate in accordance with its approval, the provisions of the Atomic Energy Act, and the NRC's regulations. Issue Description FSAR Table 6.3-4 specifies the supplemental boron lower mixing tube and dissolver Quality Group classification as "N/A." During the audit, NuScale stated that the components of the ESB are not pressure retaining and are not considered in the scope of the ASME BPV Code. The staff understands the basis for this explanation. The ESB, however, is a safety-related feature of the ECCS and is therefore considered important to safety in the context of GDC 1 and subject to the regulatory positions described in RG 1.26. Specifically, RG 1.26 states "systems or portions NuScale Nonproprietary NuScale Nonproprietary

of systems important to safety that are designed for (1) reactor shutdown or (2) residual heat removal" should be classified as Quality Group B. Information Requested In lieu of applying a generally recognized code or standard (e.g., the ASME BPV Code) to the ESB components, NuScale is requested to describe the design rules or augmented quality provisions that are assigned to the ESB components to ensure they are designed and constructed such that they will be capable of performing their safety-related functions and satisfy the requirements of GDC 1. NuScale Response: This request for additional information (RAI) is an extension of audit item A-6.3-11. NuScale provided an initial response to that request. However, the NRC staff requested more information. Specifically, NuScale and the staff engaged in a clarification call on September 10th, clarifying the staffs request for more information. During the clarification call, the staff stated they are looking for a similar level of design information for ESB components to that provided in US600 design certification Final Safety Analysis Report (FSAR) Section 3.9.4.2 for the non-Code components of the control rod drive system. In response, NuScale revises the FSAR to include a comparable level of information for ESB component design. While ESB components are not within jurisdiction of the ASME BPVC Section III, NuScale applies appropriate quality assurance and design requirements commensurate with ESBs safety-related function. (( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary

(( }}2(a),(c),ECI Audit response A-6.3-11 provides the basis and justification for the non-ASME Code applicability to ESB components. Impact on US460 SDAA: FSAR Section 3.9 has been revised as described in the response above and as shown in the markup provided in this response. NuScale Nonproprietary NuScale Nonproprietary

NuScale Final Safety Analysis Report Mechanical Systems and Components NuScale US460 SDAA 3.9-32 Draft Revision 2 3.9.3.5 Non-Code Components and Component Supports Audit Question A-6.3-11 The safety-related ECCS Supplemental Boron (ESB) components and component supports are non-code Seismic Category I components whose classifications are listed in SDAA Section 6.3 Table 6.3-5. The design of ESB safety-related components and component supports withstand the effects of an SSE and maintain their structural and functional integrity. Audit Question A-6.3-11 The ESB components are non-pressure retaining, therefore the design, fabrication, inspection, and testing are not under the jurisdiction of ASME BPVC. Safety-related ESB components withstand applicable loads for design basis events and the stress limits specific to the material specification mechanical property requirements to maintain their structural and functional integrity. 3.9.4 Control Rod Drive System The control rod drive system (CRDS) consists of the CRDMs and mechanical components that provide the means for CRA insertion into the core as described in Section 4.6, as well as the rod position indication to the module control system. The CRDM control cabinets, rod position indication cabinets and associated cables, plus the CRDS cooling water piping inside containment, are part of the CRDS. The CRDM is an electro-magnetic device that moves the CRA in and out of the nuclear reactor core and is tracked by two independent rod position indication trains. The CRDS provides one of the independent reactivity control systems as discussed in GDC 26 and GDC 27. The control rods and their drive mechanisms are capable of reliably controlling reactivity, including the safety-related function of shutting down the reactor, under conditions of normal operation, including AOOs, or under postulated accident conditions. The CRDM internal moving components, consisting of the latch mechanism and control rod drive shaft are safety-related. A positive means of insertion of the control rods is maintained and, combined with the design of the CRDS, provides margin for malfunctions such as a stuck rod (Section 4.3.1.5). The CRDM internals that ensure positive CRA insertion consist of the latch mechanism and control rod drive shaft and are classified as safety-related and non-risk-significant. Portions of the CRDS are a part of the RCPB (specifically, the pressure housings of the CRDMs) and are safety-related. The system is designed, fabricated, and tested to quality standards commensurate with the safety-related functions to be performed. The design, fabrication, and construction complies with the ASME codes in accordance with 10 CFR 50.55a (Section 3.9.4.2), providing assurance the CRDS is capable of performing its safety-related functions by withstanding the effects of AOOs, postulated accidents, and natural phenomena such as earthquakes, as discussed in GDC 1, 2, 14, 26, 27, and 29.

RAIO-175965 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360.0500 Fax 541.207.3928 www.nuscalepower.com Affidavit of Mark W. Shaver, AF-175966

AF-175966 Page 1 of 2

NuScale Power, LLC AFFIDAVIT of Mark W. Shaver I, Mark W. Shaver, state as follows: (1) I am the Director of Regulatory Affairs of NuScale Power, LLC (NuScale), and as such, I have been specifically delegated the function of reviewing the information described in this Affidavit that NuScale seeks to have withheld from public disclosure, and am authorized to apply for its withholding on behalf of NuScale. (2) I am knowledgeable of the criteria and procedures used by NuScale in designating information as a trade secret, privileged, or as confidential commercial or financial information. This request to withhold information from public disclosure is driven by one or more of the following: (a) The information requested to be withheld reveals distinguishing aspects of a process (or component, structure, tool, method, etc.) whose use by NuScale competitors, without a license from NuScale, would constitute a competitive economic disadvantage to NuScale. (b) The information requested to be withheld consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), and the application of the data secures a competitive economic advantage, as described more fully in paragraph 3 of this Affidavit. (c) Use by a competitor of the information requested to be withheld would reduce the competitors expenditure of resources, or improve its competitive position, in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product. (d) The information requested to be withheld reveals cost or price information, production capabilities, budget levels, or commercial strategies of NuScale. (e) The information requested to be withheld consists of patentable ideas. (3) Public disclosure of the information sought to be withheld is likely to cause substantial harm to NuScales competitive position and foreclose or reduce the availability of profit-making opportunities. The accompanying Request for Additional Information response reveals distinguishing aspects about the response by which NuScale develops its NuScale Power, LLC Response to NRC Request for Additional Information (RAI No. 10350 R1, Questions 6.3-9, 6.3-10, and 6.3-11) on the NuScale Standard Design Approval Application. NuScale has performed significant research and evaluation to develop a basis for this response and has invested significant resources, including the expenditure of a considerable sum of money. The precise financial value of the information is difficult to quantify, but it is a key element of the design basis for a NuScale plant and, therefore, has substantial value to NuScale. If the information were disclosed to the public, NuScales competitors would have access to the information without purchasing the right to use it or having been required to undertake a similar expenditure of resources. Such disclosure would constitute a misappropriation of NuScales intellectual property, and would deprive NuScale of the opportunity to exercise its competitive advantage to seek an adequate return on its investment. (4) The information sought to be withheld is in the enclosed response to NRC Request for Additional Information RAI 10350 R1, Questions 6.3-9, 6.3-10, and 6.3-11. The enclosure contains the designation Proprietary at the top of each page containing proprietary information. The information considered by NuScale to be proprietary is identified within double braces, (( }} in the document.

AF-175966 Page 2 of 2 (5) The basis for proposing that the information be withheld is that NuScale treats the information as a trade secret, privileged, or as confidential commercial or financial information. NuScale relies upon the exemption from disclosure set forth in the Freedom of Information Act (FOIA), 5 USC § 552(b)(4), as well as exemptions applicable to the NRC under 10 CFR §§ 2.390(a)(4) and 9.17(a)(4). (6) Pursuant to the provisions set forth in 10 CFR § 2.390(b)(4), the following is provided for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld: (a) The information sought to be withheld is owned and has been held in confidence by NuScale. (b) The information is of a sort customarily held in confidence by NuScale and, to the best of my knowledge and belief, consistently has been held in confidence by NuScale. The procedure for approval of external release of such information typically requires review by the staff manager, project manager, chief technology officer or other equivalent authority, or the manager of the cognizant marketing function (or his delegate), for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside NuScale are limited to regulatory bodies, customers and potential customers and their agents, suppliers, licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or contractual agreements to maintain confidentiality. (c) The information is being transmitted to and received by the NRC in confidence. (d) No public disclosure of the information has been made, and it is not available in public sources. All disclosures to third parties, including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or contractual agreements that provide for maintenance of the information in confidence. (e) Public disclosure of the information is likely to cause substantial harm to the competitive position of NuScale, taking into account the value of the information to NuScale, the amount of effort and money expended by NuScale in developing the information, and the difficulty others would have in acquiring or duplicating the information. The information sought to be withheld is part of NuScales technology that provides NuScale with a competitive advantage over other firms in the industry. NuScale has invested significant human and financial capital in developing this technology and NuScale believes it would be difficult for others to duplicate the technology without access to the information sought to be withheld. I declare under penalty of perjury that the foregoing is true and correct. Executed on November 20, 2024. Mark W. Shaver}}