ML24136A068
| ML24136A068 | |
| Person / Time | |
|---|---|
| Site: | Hermes File:Kairos Power icon.png |
| Issue date: | 05/10/2024 |
| From: | Office of Nuclear Reactor Regulation |
| To: | NRC/NRR/DANU |
| References | |
| Download: ML24136A068 (38) | |
Text
From: Michael Orenak Sent: Friday, May 10, 2024 3:54 PM To: Weidong Wang; Larry Burkhart Cc: Cayetano Santos; Matthew Hiser; Brian Bettes; Josh Borromeo
Subject:
Preliminary Chapters (2 & 3) of Hermes 2 SE to ACRS Attachments: Chapter 02 - Site Characteristics.pdf; Chapter 03 - Design of Structures Systems and Components.pdf
- Weidong,
Attached is two more of the preliminary chapters (2 & 3) from the safety evaluation (SE) for the Hermes 2 construction permit application. These chapters have been reviewed by branch chiefs and received a preliminary review by OGC. However, these chapters are not final because it still needs to be reviewed by division management and receive the final OGC review. Thus, these preliminary chapters could change between now and the approved SE that will be sent to ACRS for formal review. I am sending these chapters in advance so that members can become familiar with the safety evaluation and begin preparing for the formal review.
Thirteen preliminary chapters were provided to you on March 14, April 4, April 22, and April 24, 2024. If possible, I will send the remaining preliminary chapters (5, 9, and 13) to you piecemeal after they receive the preliminary OGC for the second and third planned subcommittee meetings on June 4 and June 12, 2024.
Kairos Power submitted Revision 0 of the preliminary safety analysis report (PSAR) for Hermes 2 in July 2023. All preliminary SE chapters being sent to the ACRS refer to Revision 1 of the PSAR. Although Revision 1 of the PSAR has not been submitted, Kairos stated their intent to do so once all PSAR changes are known (i.e., the end of the technical review). The current list of docketed PSAR changes that will be incorporated into Revision 1 of the PSAR can be found in ADAMS and on the NRC public webpage at https://www.nrc.gov/reactors/non-power/new-facility-licensing/hermes2-kairos/documents.html.
The staff has taken a different approach toward the Hermes 2 SE considering that Hermes 1 and Hermes 2 CP applications have most of the same information. Due to these similarities, the staff leveraged the Hermes 1 SE to the extent possible for Hermes 2, using an incorporation by reference for many sections. The following description, taken from Chapter 1 of the Hermes 2 SE, discusses how the staffs review of Hermes 1 was applied to its review of the Hermes 2:
Use of Docketed Information
The staffs review of the Hermes 2 CP application was informed by the Hermes 1 CP application review. The Hermes 2 facility includes many SSCs that are identical to those that would be used in the Hermes 1 facility. Accordingly, large portions of the Hermes 1 PSAR are identical to the Hermes 2 PSAR. In the July 14, 2023, CP application submittal, Kairos highlighted the differences between the Hermes 1 and Hermes 2 PSARs in two ways. First, Kairos used blue font in the Hermes 2 PSAR to identify any modified or new text. Second, Kairos provided a summary of the information deleted from the Hermes 1 PSAR to generate the Hermes 2 PSAR (ML23195A132).
In addition, Kairos identified the docketed information and audit information from Hermes 1 that is applicable to the Hermes 2 CP application in two letters dated October 27, 2023 (ML23300A141 and ML22300A144). This information is considered docketed information for the Hermes 2 CP application and was used to inform the staffs review.
Format and Content of Hermes 2 Safety Evaluation Sections
Based on the consistencies between the Hermes 1 and Hermes 2 PSARs described above, the staff leveraged the Hermes 1 SE to the greatest extent possible to support its review of the Hermes 2 CP application. Accordingly, applicable contents of the Hermes 1 SE were incorporated by reference into this SE. To determine which Hermes 1 SE content could be incorporated by reference, the staff reviewed the differences between the Hermes 1 and Hermes 2 PSARs. Where the Hermes 2 PSAR only contained minor deviations (e.g., minimal or no effect on the NRC SE or editorial changes, as compared to the Hermes 1 PSAR), the staffs SE was largely limited to incorporating by reference applicable portions of the Hermes 1 SE. Similarly, where the Hermes 2 PSAR contained a limited number of significant but discrete changes, but was otherwise identical to the Hermes 1 PSAR, the staffs SE was likewise limited to an evaluation of the variances between the two PSARs. In this case, the balance of the staffs SE also incorporated by reference applicable portions of the Hermes 1 SE. Based on this approach, many of the Hermes 2 SE sections are organized using the following structure:
- Brief introduction summarizing the Hermes 2 PSAR content with a focus on any changes in comparison to the Hermes 1 PSAR.
- Regulatory evaluation section that, in most cases, incorporates by reference the regulations and guidance from the corresponding section of the Hermes 1 SE due to the similarities between the Hermes 1 and Hermes 2 facility designs.
- Technical evaluation that:
o Identifies the consistent and modified Hermes 2 PSAR information, as compared to the Hermes 1 PSAR.
o Incorporates by reference, as appropriate, content from the Hermes 1 SE for PSAR information that is consistent between Hermes 1 and Hermes 2.
o Evaluates the new design information and non-editorial changes (i.e.,
minor and/or few significant changes), as compared to the Hermes 1 SE.
The depth of the staff review provided for each change is dependent on the significance of that change.
- A full conclusion specific to the Hermes 2 review.
For Hermes 2 PSAR sections that contain entirely new information and/or several significant changes when compared to the Hermes 1 PSAR, the staff performed its evaluation without incorporation by reference from the Hermes 1 SE. One example of a section which reflects such an evaluation by the staff is Section 5.2, Intermediate Heat Transport System, of this SE related to the intermediate salt loops. These systems are not in the design of the Hermes 1 test reactor; therefore, they were not evaluated by the staff in its review of the Hermes 1 CP application. Accordingly, the staff evaluated this system without incorporation by reference of the Hermes 1 SE.
If you have any questions, please contact me, Tanny Santos, or Matt Hiser.
- Mike Orenak
Hearing Identifier: Kairos_Hermes2_CPDocs_Public Email Number: 16
Mail Envelope Properties (SA1PR09MB87840EF21DBF84BDECF5733280E72)
Subject:
Preliminary Chapters (2 & 3) of Hermes 2 SE to ACRS Sent Date: 5/10/2024 3:54:19 PM Received Date: 5/10/2024 3:54:23 PM From: Michael Orenak
Created By: Michael.Orenak@nrc.gov
Recipients:
"Cayetano Santos" <Cayetano.Santos@nrc.gov>
Tracking Status: None "Matthew Hiser" <Matthew.Hiser@nrc.gov>
Tracking Status: None "Brian Bettes" <Brian.Bettes@nrc.gov>
Tracking Status: None "Josh Borromeo" <Joshua.Borromeo@nrc.gov>
Tracking Status: None "Weidong Wang" <Weidong.Wang@nrc.gov>
Tracking Status: None "Larry Burkhart" <Lawrence.Burkhart@nrc.gov>
Tracking Status: None
Post Office: SA1PR09MB8784.namprd09.prod.outlook.com
Files Size Date & Time MESSAGE 6031 5/10/2024 3:54:23 PM Chapter 02 - Site Characteristics.pdf 369053 Chapter 03 - Design of Structures Systems and Components.pdf 319805
Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
THIS NRC STAFF DRAFT SE HAS BEEN PREPARED AND IS BEING RELEASED TO SUPPORT INTERACTIONS WITH THE ACRS. THIS DRAFT SE HAS NOT BEEN SUBJECT TO FULL NRC MANAGEMENT AND LEGAL REVIEWS AND APPROVALS, AND ITS CONTENTS SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITIONS. 1
2 SITE CHARACTERISTICS
The purpose of evaluating the site characteristics of a proposed reactor facility is to determine whether the site selected is suitable for constructing and operating the proposed facility. Site characteristics include geography and demography; nearby industrial, transportation, and military facilities; meteorology; hydrology; and geology, seismology, and geotechnical engineering.
This chapter of the Hermes 2 construction permit (CP) safety evaluation (SE) describes the U.S.
Nuclear Regulatory Commission (NRC) staffs (the staffs) technical review and evaluation of the preliminary information on site characteristics provided in Chapter 2, Site Characteristics, of the Hermes 2 preliminary safety analysis report (PSAR), Revision 1. The staff reviewed PSAR Chapter 2 against applicable regulatory requirements using regulatory guidance and standards to assess the sufficiency of the preliminary information on site characteristics for the issuance of CPs in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 50, "Domestic Licensing of Production and Utilization Facilities.
2.1 Geography and Demography
2.1.1 Introduction
Section 2.1, Geography and Demography, of the Hermes 2 PSAR describes the proposed Hermes 2 site and its surroundings, including population distributions for the area around the site.
2.1.2 Regulatory Evaluation
The staff reviewed Section 2.1.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facility designs and the consistency of the site geography and demography between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 2.1.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 2.1.2 of the Hermes 1 SE.
2.1.3 Technical Evaluation
The staff reviewed Section 2.1 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 2.1, Geography and Demography). The staff found that Section 2.1 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for a few minor changes and a few significant changes, which are evaluated below in Section 2.1.3.1 and Section 2.1.3.2, respectively. The staff found that the following portions of Section 2.1 in the Hermes 2 PSAR contain information consistent with the Hermes 1 PSAR (e.g., minor or editorial changes only):
x Section 2.1.1.1, Specification and Location x Section 2.1.1.2, Boundary and Zone Area Maps Since the Hermes 2 site geography and demography largely remain identical, apart from the differences evaluated below, Section 2.1 of the Hermes 2 PSAR contains information consistent with Section 2.1 of the Hermes 1 PSAR. Based on these consistencies, this section incorporates by reference Section 2.1.3, Technical Evaluation, of the Hermes 1 SE.
2.1.3.1 Minor Changes Compared to the Hermes 1 PSAR
The minor changes in Hermes 2 PSAR Section 2.1, as compared to the information in Hermes 1 PSAR Section 2.1, include the following:
- The latitude and longitude, Universal Transverse Mercator coordinates, and Roane County State Plane coordinates for the location of the Hermes 2 reactor facility are provided.
- The Hermes 1 facility was added to the list of prominent natural and man-made features within approximately 5 miles (8 kilometers (km)) of the proposed Hermes 2.
- PSAR Figures 2.1-2, Prominent Features in Site Area, and 2.1-3, Project Site Area and Zones Associated with the Facility, were updated to show the nearest full time resident and to show the Hermes 2 facility, respectively.
Kairos provided the coordinates of the proposed Hermes 2 facility in latitude and longitude, Universal Transverse Mercator, and Roane County State Plane. The staff confirms that these coordinate values are accurate for the Hermes 2 facility. In addition, Kairos added the Hermes 1 facility to the list of prominent natural and man-made features within approximately 5 miles (8 km) of the proposed reactor facility (i.e., Hermes 2). The addition of the Hermes 1 facility to the list is appropriate because it will be a prominent feature when the Hermes 2 facility is being constructed and operated. Kairos updated Figure 2.1-2 to identify that the nearest full time resident lives approximately 1/2 mile closer than previously known at the time that the Hermes 1 CP application was reviewed and updated Figure 2.1-3 to include the Hermes 2 facility. The staff determined that the updates to Figures 2.1-2 and 2.1-3 are appropriate because they account for the most recent knowledge about the proposed Hermes 1 and Hermes 2 sites and local area. Based on the above, the staff finds that the Hermes 2 coordinates, the addition of Hermes 1 facility to list of prominent and man-made features, and the updates to Figures 2.1-2 and 2.1-3, are acceptable.
2.1.3.2 Significant Changes Compared to the Hermes 1 PSAR
Significant changes contained in Section 2.1 of the Hermes 2 PSAR, as compared to Section 2.1 of the Hermes 1 PSAR, include information regarding the following:
- Revision to the distribution of resident population within 5 miles (8 km) from the proposed reactor facility site in both Roane and Morgan counties.
These changes are identified in:
- Section 2.1.2, Population Distribution
- Table 2.1-1, Resident Population Distribution within 5 miles (8 km) of the Site in Roane County
- Table 2.1-2, Resident Population Distribution within 5 miles (8 km) of the Site in Morgan County
- Figure 2.1-5, Resident Population Distribution - 2020
- Figure 2.1-6, Resident Population Distribution - 2026
- Figure 2.1-7, Resident Population Distribution - 2031
- Figure 2.1-8, Resident Population Distribution - 2040
The staff evaluated the sufficiency of this additional preliminary information regarding resident population distribution surrounding the proposed Hermes 2 site using the guidance and acceptance criteria from Section 2.1, Geography and Demography, of NUREG-1537, Parts 1 and 2. Section 2.1.2, Population Distribution, of the Hermes 2 PSAR describes the distribution of resident and transient populations within 5mi les (8 km) of the center point of the proposed site for the years 2026 (the beginning of the requested construction period), 2031, and 2040 (the approximate end of the requested 11-year license period), as described in Hermes 2 PSAR Tables 2.1-1 and 2.1-2 and PSAR Figures 2.1-5 through 2.1-8 using the 2020 decennial census data to project the population distribution. In these PSAR tables and figures, the projected population is presented in five distance bands, represented by concentric circles: 0 to 0.5 miles (0 to 0.8 km), 0.5 to 1 mile (0.8 to 1.6 km), 1 to 2 miles (1.6 to 3.2 km), 2 to 3 miles (3.2 to 4.8 km), and 3 to 5 miles (4.8 to 8 km). Each distance band is subdivided into 16 equal directional sectors. Kaiross estimated population distributions for 2026, 2031, and 2041, are based on estimates for Roane and Morgan counties from the Boyd Center for Business and Economic Research, the demographer for the State of Tennessee. Because there are no schools or lodging facilities within 5 miles (8 km) of the proposed site, Kairos concluded that there is zero transient population in the area.
The staff finds the change in population distribution surrounding the proposed site for the Hermes 2 facility is acceptable as it is based on the most current (2020) census data. In addition, the population distribution for Roane and Morgan counties near the proposed site projected for 2026, 2031, and 2041, are based on estimates from the official demographer for the State of Tennessee using the 2020 census data. Based on the above, the staff finds the updated population distribution surrounding the proposed site for the Hermes 2 reactors acceptable.
Based on its review, the staff determined that the geographical and demographical information provided in the Hermes 2 PSAR is sufficiently detailed and accurate to provide the necessary bases to allow accurate assessments of the potential radiological impact on the public resulting from the siting and operation of the proposed Hermes 2 facility, including analysis (e.g., dose calculations) presented in other PSAR chapters. The staff also finds that no geographic or demographic characteristics of the Hermes 2 site render the site unsuitable for operation of the Hermes 2 facility, and that the information provided meets the applicable acceptance criteria of NUREG-1537, Part 2, Section 2.1. Accordingly, the staff finds that the level of detail provided on geography and demography demonstrates an adequate design basis for the Hermes 2 facility.
2.1.4 Conclusion
Based on the s taff findings above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the information in Hermes 2 PSAR Section 2.1 is sufficient and meets the applicable guidance and regulatory requirements identified in this section for the issuance of CPs in accordance with 10 CFR 50.35, Issuance of construction permits, and 10 CFR 50.40, Common standards.
2.2 Nearby Industrial, Transportation, and Military Facilities
2.2.1 Introduction
Section 2.2, Nearby Industrial, Transportation, and Military Installations, of the Hermes 2 PSAR describes the present and projected future industrial, transportation, and military installations and operations in the area around the proposed Hermes 2 site.
2.2.2 Regulatory Evaluation
The staff reviewed Section 2.2.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facility designs and the consistency of the nearby industrial, transportation, and military facilities between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 2.2.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 2.2.2 of the Hermes 1 SE.
2.2.3 Technical Evaluation
The staff reviewed Section 2.2 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 2.2, Nearby Industrial, Transportation, and Military Installations). The staff found that Section 2.2 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for a few significant changes, which are evaluated below in SE Section 2.2.3.1. The staff found that the following portions of Section 2.2 in the Hermes 2 PSAR contain information consistent with the Hermes 1 PSAR (e.g., minor or editorial changes only):
- Section 2.2, Nearby Industrial, Transportation, and Military Installations
- Sections 2.2.1.1, Description of Pipelines, through 2.2.1.4, Description of Railroads
- Sections 2.2.2.1, Identification of Air Traffic Near the Site, through 2.2.2.3, Evaluation of Airport Hazards and Helicopter Operations
- Sections 2.2.3.2, Flammable Vapor Clouds, through 2.2.3.4, Fires Since the Hermes 2 site location largely remains identical to Hermes 1, apart from the differences evaluated below, the discussion of nearby industrial, transportation, and military facilities in Section 2.2 of the Hermes 2 PSAR contains information consistent with Section 2.2 of the Hermes 1 PSAR. Based on these consistencies, this section incorporates by reference Section 2.2.3, Technical Evaluation, of the Hermes 1 SE.
2.2.3.1 Significant Changes Compared to the Hermes 1 PSAR
The significant changes in Hermes 2 PSAR Section 2.2, as compared to the information in Hermes 1 PSAR Section 2.2, include the following:
- Effective area of the Hermes 2 facility
- Increased aircraft accident frequency for the site
- Addition of four facilities on the list of facilities within 5 miles (8 km) of the proposed site
These changes are identified in the following portions of the Hermes 2 PSAR:
- Table 2.2-7, Calculated Effective Areas of Safety Related Structures (square miles) by Aircraft Type Used for the Evaluation of Airways and Airport
- Section 2.2.2.4, Summary of Risks from Air Traffic and Table 2.2-9, Total Crash Probability
- Section 2.2.1, Locations and Routes, Section 2.2.3, Analysis of Potential Accidents at Facilities, Section 2.2.3.1, Explosions, Table 2.2-1, Nearby Facilities, Table 2.2-2, Facilities Unable to Affect the Facility, Table 2.2-3, Nearby Facility Chemical Storage, and Table 2.2-10, Evaluation of Chemical Explosion Hazards Near the Site
As Hermes 2 is a two-unit facility, compared to the single-unit Hermes 1 facility, the effective area of the reactor facility considered for evaluating aircraft crash hazards will be larger than that of the Hermes 1 facility, as reflected in PSAR Table 2.2-7. Accordingly, since the footprint of each Hermes 2 reactor is the same as that of the Hermes 1 reactor, the effective area of the Hermes 2 reactor facility corresponding to each aircraft type is twice that assumed for Hermes 1. The staff finds that the estimated effective areas denoted in Hermes 2 PSAR Table 2.2-7 for evaluating crash hazards from different types of aircraft flying in the vicinity of the proposed site are appropriate based on the size of the facility.
To assess the projected number of flights at the proposed Oak Ridge Airport, Kairos used the environmental assessment (EA) prepared by the U.S. Department of Energy (DOE) for transferring the property to develop the general aviation airport (DOE, 2016). Additionally, Kairos used the same air traffic information used for Hermes 1 of the Jet Route J46 and the Victor Route V16. The staff reviewed the EA prepared by the DOE for transferring the property and a draft EA of the proposed Oak Ridge Airport developed by the Federal Aviation Administration (FAA) (FAA, 2023). The runway of the proposed airport was shifted slightly to the southeast increasing the distance from the Hermes 2 facility, when compared to the evaluations performed for Hermes 1.
In addition, based on the airport master plan, the draft FAA EA indicates that there will be 14,796 forecasted annual operations by general aviation aircraft in 2025 and 15,906 in 2040.
The forecasted number of operations at the proposed Oak Ridge Airport is smaller (approximately 32 percent) than that given in Table 2.4, Oak Ridge Local and Itinerant Operations Forecast, of the DOE EA. The staff finds that the DOE EA has given the average of the operations at six nearby airports by the general aviation aircraft. As the number of operations given in the draft FAA EA is based on the airport m aster plan and would therefore be considered more specific to the proposed site, the staff used the number of operations forecasted in the draft FAA EA as the anticipated number of annual general aviation aircraft operations for the current hazard assessment.
Using the forecasted number of operations at the proposed Oak Ridge Airport from the draft FAA EA, the estimated annual crash frequency will be smaller than that provided in Hermes 2 PSAR Table 2.2-9; Total Crash Probability. While the staff determined that the annual crash frequency estimated by Kairos is conservative, the estimated total annual crash frequency would still be above the credible hazard threshold. Therefore, Kairos stated that for all cases, the annual crash frequency criterion is exceeded due to general aviation aircraft use at the proposed Oak Ridge Airport. Consequently, in Hermes 2 PSAR Sections 2.2.2.4 and 3.5, Plant Structures, Kairos stated that the safety -related portion of the two reactor buildings will be designed to withstand the impact of a general aviation aircraft. The staff will review the basis for selecting the critical aircraft type for designing the safety-related portion of the reactor buildings during a future review of the operating license (OL) application of the Hermes 2 facility.
In Hermes 2 PSAR Section 2.2.3 and Table 2.2-1, Kairos identified four additional nearby facilities at which an accident can potentially affect the proposed Hermes 2 reactor facility:
- 1. Hermes 1 Facility: This facility will be located within the site boundary. This facility has received a construction permit from the NRC. The Hermes 1 PSAR states that the offsite radiological impacts during routine operations and severe accidents of the facility would be within the regulatory limits. The Hermes 1 facility will have an on-site diesel fuel tank with the capacity of 21,555 gallons (81,595 liters). In addition, the Hermes 1 facility will have an inventory of 40,000 pounds (18,144 kilograms ) of low-pressure molten salt coolant (Flibe); however, the quantities of other chemicals are not yet finalized. In addition, the locations of all on-site chemicals at the Hermes 1 facility are not yet finalized. Kairos analyzed the potential overpressure assuming the on-site diesel storage tank at its upper fire/explosion limit. The safe distance at which the overpressure is below 1 psi (6.7 kilopascals ) is estimated to be 0.09 miles (0.14 km). Kairos will analyze the potential thermal radiation to be experienced by the safety-related structures, systems, and components at the Hermes 2 facility that could result from a fire at the Hermes 1 on-site diesel storage tank as part of the Hermes 2 OL application.
Additionally, the staff will evaluate the potential thermal radiation during its review of the Hermes 2 OL application.
- 2. Kairos Power Atlas Fuel Fabrication Facility: This is a tristructural isotropic (TRISO)-based nuclear fuel fabrication facility that Kairos has proposed locating within the site boundary of the Hermes 2 facility. Kairos will analyze the potential hazards from this facility in the Hermes 2 OL application. The staff will evaluate the potential hazards from the Kairos Power Atlas Fuel Fabrication Facility during its review of the Hermes 2 OL application.
- 3. TRISO-X Fuel Facility: This is a TRISO-based nuclear fuel fabrication facility that would be located at the nearby Horizon Center, approximately 2.4 miles (3.9 km) northeast of the proposed Hermes 2 facility. Kairos will analyze the potential hazards from this facility in the OL application. The staff will evaluate the potential hazards from the TRISO-X Fuel Facility during its review of the Hermes 2 OL application.
- 4. Ultra Safe Nuclear Corporation Pilot Fuel Manufacturing Facility: This is a TRISO-based nuclear fuel fabrication facility located approximately 0.8 miles (1.3 km) southeast of the proposed Hermes 2 facility at the East Tennessee Technology Park (ETTP). The Hermes 2 PSAR does not have further information on this facility. Kairos is collecting information on this facility and potential hazards to the proposed Hermes 2 facility will be analyzed in the Hermes 2 OL application. The staff will evaluate the potential hazards from the Ultra Safe Nuclear Corporation Pilot Fuel Manufacturing Facility during its review of the Hermes 2 OL application.
The staff finds that these four facilities are sufficiently close to the location of the Hermes 2 reactors and an accident at any of these facilities can potentially affect the safe operation of the Hermes 2 facility. The inclusion of these nearby facilities for assessing potential hazards to the Hermes 2 reactors presents a complete and current overview of facilities, activities, and materials located in the vicinity of the proposed reactor site and, therefore, is acceptable.
Based on its review, the staff determined that the level of detail and analyses provided on nearby industrial facilities, transportation routes, and military facilities demonstrate an adequate design basis and satisfy the applicable acceptance criteria of NUREG-1537, Part 2, Section 2.2, allowing the staff to find that:
- The information in the PSAR is sufficiently detailed to provide an accurate description of the nearby facilities and transportation routes and hazards to the proposed facility posed by them.
- The description of the hazards and their assessments are adequate to determine potential radiological impact on the public resulting from the siting and operation of the proposed reactor facility.
- Potential hazards associated with nearby transportation routes and industrial and military facilities will pose no undue risk to the proposed facility as the facility is either designed against it (e.g., aircraft crash hazard) or the hazard is not a credible hazard to the proposed facility.
2.2.4 Conclusion
Based on the s taff findings above, and as incorporated by reference from the Hermes 1 SE, the staff concludes the information on nearby industrial, military, and transportation facilities in Hermes 2 PSAR Section 2.2 is sufficient and meets the applicable guidance and regulatory requirements identified in this SE section for the issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further technical or design details required to complete the safety analysis may reasonably be left for later consideration and the staff will confirm that the final design conforms to this design basis during the evaluation of the Hermes 2 OL application.
2.3 Meteorology
2.3.1 Introduction
Section 2.3, Meteorology, of the Hermes 2 PSAR describes the general climate of the region around the proposed Hermes 2 site and meteorological conditions relevant to the design and operation of the Hermes 2 facility. PSAR Section 2.3 also provides data and information used to determine the atmospheric dispersion conditions in the vicinity of the site. This information includes local and regional airflow and meteorological measurements used for dispersion estimates.
2.3.2 Regulatory Evaluation
The staff reviewed Section 2.3.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facility designs and the consistency of the meteorology between Hermes 1 and Hermes 2 (i.e., the proposed sites are collocated), the staff finds that the regulations and guidance listed in Section 2.3.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 2.3.2 of the Hermes 1 SE.
2.3.3 Technical Evaluation
The staff reviewed Section 2.3, Meteorology, of the Hermes 2 PSAR and compared it to the equivalent material in the Hermes 1 PSAR (Section 2.3, Meteorology). The staff found that the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for a few minor changes, which are evaluated below. The staff also verified that the Hermes 2 site meteorological data remain almost identical to Hermes 1. Based on these consistencies, this section incorporates by reference Section 2.3.3 of the Hermes 1 SE.
2.3.3.1 Minor Changes Compared to the Hermes 1 PSAR
The minor changes in Hermes 2 PSAR Section 2.3, as compared to the information in Hermes 1 PSAR Section 2.3, include the following:
- Changes in years of data collection, daily temperature (degrees Fahrenheit (°F)), relative humidity and precipitation for the Oak Ridge area
- Collection of thunderstorm data increased by one year
- Changes to years of reports for hail and increase on reported instances of severe hail for Knox county
- Increase in the number of lightning strikes and changes to the proximity of lightning strikes to the site
- Increase in years taken into consideration from the tornado events databases
- Description of tropical systems and hurricanes near the site for years 2021 and 2022
- The expected licensed period of operation for Hermes 2 is approximately 11 years; the expected period of operation for Hermes 1 is 4 years
In Hermes 2 PSAR Section 2.3.1, Regional Climatology, Kairos provided changes to the data period used and the daily minimum and maximum temperature (°F), the data period and the regional average for relative humidity, and data related to annual precipitation and the wettest and driest seasons for the Oak Ridge area. The staff reviewed the information on the regional climatology of the proposed Hermes 2 site, including verification that Kairos obtained the information from appropriate sources and that the information is consistent with other available data. The staff determined the information appears reasonable for the geographic area andthat Kaiross assessment is sufficient for evaluation of the regional climatology to inform the design bases for the Hermes 2 facility. Based on the above, the staff finds that the assessment of the regional climatology is acceptable.
Hermes 2 PSAR Section 2.3.1.2, Thunderstorms, states that the data collection pe riod is from 2001-2021, which is an increase of 1 year from the Hermes 1 CP application. The staff reviewed the information on thunderstorms in the region of the proposed Hermes 2 site, including verification that Kairos obtained the information from appropriate sources and that the information is consistent with other available data. The staff determined that the information appears reasonable for the geographic area and that Kaiross assessment is sufficient for the evaluation of potential thunderstorm impacts on Hermes 2 to inform the design bases for the Hermes 2 facility. Based on the above, the staff finds that the assessment of thunderstorms is acceptable.
Hermes 2 PSAR Section 2.3.1.3, Hail, states that the data collection period is from 1950-2022, which is an increase of 2 years from the Hermes 1 CP application. During that period, the instances of severe hail in Knox County were updated to 94. The staff reviewed the information on hail in the region of the proposed Hermes 2 site, including verification that Kairos obtained the information from appropriate sources and that the information is consistent with other available data. The staff determined that the information appears reasonable for the geographic area and that Kaiross assessment is sufficient for the evaluation of potential hail impacts on Hermes 2 to inform the design bases for the Hermes 2 facility. Based on the above, the staff finds that the assessment of hail is acceptable.
Hermes 2 PSAR Section 2.3.1.4, Lightning, states that, during the review period, 7 of the 10 years had a lightning strike occurring within the proposed site boundary or within 500 feet (ft.) of the site. One of these years (2012) was a year with an exceptionally high number of cloud to ground lightning strikes. Eleven lightning strikes occurred within the site boundary with several more strikes occurring within 500 ft. of the site. The staff reviewed the information on lightning in the region of the proposed Hermes 2 site, including verification that Kairos obtained the information from appropriate sources and that the information is consistent with other available data. The staff determined that the information appears reasonable for the geographic area and that Kaiross assessment is sufficient for the evaluation of potential lightning impacts on Hermes 2 to inform the design bases for the Hermes 2 facility. Based on the above, the staff finds that the assessment of lightning is acceptable.
Hermes 2 PSAR Section 2.3.1.7, Tornadoes, states that the period of data review changed to a 73-year period of 1950-2022. The staff reviewed the information regarding tornadoes in the region of the proposed Hermes 2 site, including verification that Kairos obtained the information from appropriate sources and that the information is consistent with other available data. The staff determined that the information appears reasonable for the geographic area and that Kaiross assessment is sufficient for the evaluation of potential impacts from tornadoes on Hermes 2 to inform the design bases for the Hermes 2 facility. Based on the above, the staff finds that the assessment of tornadoes is acceptable.
Hermes 2 PSAR Section 2.3.1.8, Hurricanes, states that there have been 12 tropical storms within a 50 mile radius of the site. The PSAR states that in 2021, two tropical systems passed within a 50 mile radius of the site, but both were tropical depressions when they passed through the area. PSAR Section 2.3.1.8 states that in 2022, a system which had been classified as a hurricane came within a 50 mile radius of the site, but by the time it reached the area, it was downgraded to a tropical depression, and dissipated over eastern Tennessee. The staff reviewed the information on hurricanes in the region of the proposed Hermes 2 site, including verification that Kairos obtained the information from appropriate sources and that the information is consistent with other available data. The staff determined that the information appears reasonable for the geographic area and that Kaiross assessment is sufficient for the evaluation of potential impacts from hurricanes on Hermes 2 to inform the design bases for the Hermes 2 facility. Based on the above, the staff finds that the assessment of hurricanes is acceptable.
Hermes 2 PSAR Section 2.3.1.14, Climate Change, states that the approximate license period for the facility is 11 years. The staff reviewed the information related to climate change and determined that Kaiross assessments of climate information to inform the design bases for Hermes 2 are sufficient given the 11-year planned operation period for the facility and because the staff does not expect climate changes over an 11-year period to significantly impact Hermes 2 operation or the design bases. Based on the above, the staff finds that the assessment of climate change is acceptable.
On the bas is of its review, the staff finds that the level of detail provided regarding the Hermes 2 site meteorology demonstrates an adequate basis for a preliminary design and satisfies the applicable acceptance criteria of NUREG-1537, Part 2, Section 2.3, that the site area is sufficiently documented so that meteorological impacts on reactor safety and operation can be reliably predicted.
2.3.4 Conclusion
Based on the s taff findings above, and as incorporated by reference from the Hermes 1 SE, the staff concludes the information on meteorology in Hermes 2 PSAR Section 2.3 is sufficient and meets the applicable guidance and regulatory requirements identified in this SE section for the issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further information on meteorology (e.g., details regarding long-term dispersion modeling) can reasonably be left for later consideration in the OL application since this information is not necessary to be provided as part of a CP application.
2.4 Hydrology
2.4.1 Introduction
Section 2.4, Hydrology, of the Hermes 2 PSAR describes postulated hydrological events and potential flood hazards for the proposed Hermes 2 site. Kairos references hydrological information from several flood hazard study reports. Kairos stated that information in PSAR Section 2.4 supports the analyses and evaluations of the consequences of potential uncontrolled releases of radioactive material.
2.4.2 Regulatory Evaluation
The staff reviewed Section 2.4.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facility designs and the consistency of the hydrology between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 2.4.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 2.4.2 of the Hermes 1 SE.
2.4.3 Technical Evaluation
The staff reviewed Section 2.4 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 2.4, Hydrology). The staff found that Section 2.4 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for minor changes, which are evaluated below. The staff also verified that the Hermes 2 hydrology is identical to Hermes 1. Based on these consistencies, this section incorporates by reference Section 2.4.3 of the Hermes 1 SE.
2.4.3.1 Minor Changes Compared to the Hermes 1 PSAR
The minor changes in Hermes 2 PSAR Section 2.4, as compared to the information in Hermes 1 PSAR Section 2.4, include the following:
- Increased proposed operating life from 4 years (Hermes 1) to 11 years (Hermes 2)
- Table 2.4 2, Roane County FEMA FIS Flooding Elevation (Projected to Site), adds to the (**) note the following statement, on plant grade El 765 NAVD 88.
Section 2.4 of the Hermes 2 PSAR states that the intended licensing period is increased from 4 years to 11 years. The Hermes 1 SE describes staffs evaluation and findings with regard to dam safety during the facilitys 4-year operating lifetime. The staffs findings are applicable to Hermes 2s longer operating lifetime of 11 years because t he ongoing oversight and inspections carried out by the Tennessee Valley Authority (TVA) as part of its dam safety program will continue throughout the 11-year proposed licensing term of Hermes 2, providing the staff with assurance that a dam failure resulting in site flooding would be very unlikely. Additionally, as discussed in, The Status of Methods for Estimation of the Probability of Failure of Dams for Use in Quantitative Risk Assessment. International Commission on Large Dams, the probability of a sunny day dam failure is low, for both a 4-year operational life or the 11-year operational life of Hermes 2. T herefore, the associated flooding mechanism is not considered a credible hazard for a 4-year or a 11-year operating lifetime. Based on the above, the staff finds that the proposed 11-year operating lifetime is acceptable with regard to site hydrology.
The addition to the (**) note in Hermes 2 PSAR Table 2.4-2 provides additional information on the basis for the numbers in the column, Estimated Depth at Hermes 2. This addition does not change any of the technical information in the table, nor did the technical information in Table 2.4-2 change from that provided in the Hermes 1 CP application. Based on the above, the staff finds that the addition to the note is acceptable.
On the basis of its review, the staff finds that the level of detail provided regarding the Hermes 2 hydrology demonstrates an adequate basis for a preliminary design and satisfies the applicable acceptance criteria of NUREG 1537, P art 2, Section 2.4, Hydrology, that the site has been selected with due consideration of potential hydrologic events and consequences.
2.4.4 Conclusion
Based on staff findings above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the information regarding hydrology in Section 2.4 of the Hermes 2 PSAR is sufficient and meets the applicable guidance and regulatory requirements identified in this SE section for the issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further information on hydrology can reasonably be left for later consideration in the OL application since this information is not necessary to be provided as part of a CP application.
2.5 Geology, Seismology, and Geotechnical Engineering
2.5.1 Introduction
Section 2.5, Geology, Seismology, and Geotechnical Engineering, of the Hermes 2 PSAR describes the geologic, geophysical, seismic, and geotechnical characteristics of the proposed Hermes 2 site and the surrounding region.
2.5.2 Regulatory Evaluation
The staff reviewed Section 2.5.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facility designs and the consistency of the geology, seismology, and geotechnical engineering between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 2.5.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 2.5.2 of the Hermes 1 SE.
2.5.3 Technical Evaluation
The staff reviewed Section 2.5 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 2.5, Geology, Seismology, and Geotechnical Engineering).
The staff found that Section 2.5 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for a significant change, which is evaluated below in SE Section 2.5.3.1. The staff found that the following portions of Hermes 2 PSAR Section 2.5 contain information consistent with the Hermes 1 PSAR (e.g., minor or editorial changes only):
- Section 2.5.1, Regional Geology
- Section 2.5.2, Site Geology
- Section 2.5.2.2, Site Subsurface Stratigraphy, through Section 2.5.2.3.2 Subsurface Stratigraphy
- Section 2.5.3, Vibratory Ground Motion through Section 2.5.3.4.6, Enveloping Design Response Spectrum
- Section 2.5.4, Potential for Subsurface Deformation, through Section 2.5.4.2, Liquefaction Potential,
- Section 2.5.5, Foundation Interface, and 2.5.5.1, Site History
- Section 2.5.6, References
Since the design and functionality of the Hermes 2 systems remain largely identical to those of Hermes 1, apart from the differences evaluated below, Section 2.5 of the Hermes 2 PSAR contains information consistent with Section 2.5 of the Hermes 1 PSAR. Based on these consistencies, this section incorporates by reference Section 2.5.3, Technical Evaluation, of the Hermes 1 SE.
2.5.3.1 Significant Change Compared to the Hermes 1 PSAR
A significant change contained in Section 2.5 of the Hermes 2 PSAR, as compared to Section 2.5 of the Hermes 1 PSAR, includes information regarding the following:
- Plant layout and foundation interface for the Hermes 2 reactors and their relative position to Hermes 1 and Borings B-1, B-3, and B-6.
This change is identified in the following Hermes 2 PSAR sections:
- Sections 2.5.2.1, Karst, and 2.5.4.3, Karst
- Section 2.5.5.2, Plant Layout and Foundation Interface
- Figure 2.5-11, Location of the Facility at K-33, and Figure 2.5-22, Foundation Interface
The staff evaluated the sufficiency of this additional preliminary information regarding the Hermes 2 geology and geotechnical engineeringusing the guidance and acceptance criteria from Section 2.5, Geology, Seismology, and Geotechnical Engineering, of NUREG1537, Parts 1 and 2.
PSAR Figure 2.5-11 provides a plan view of the facility with the location of Hermes 2, its position relative to Hermes 1, and the borings taken at the site. PSAR Section 2.5.2.1 and Section 2.5.4.3 provide a description of the location of Borings B-1, B-3, and B-6, relative to the Hermes 2 reactors stating that [t]he location for the reactors is in the area of Boring B3 and Boring B 6, and that Boring B 1 is located more than 1000 ft. away from the proposed location of the reactors. PSAR Figure 2.5-22 provides a cross section of the reactors foundation interfaces. PSAR Section 2.5.5.2 states that, the bearing system for the safety related structures is a foundation mat resting directly over sound rock or over a thin concrete fill. It is anticipated that sound bedrock will be very close to the elevation of the bottom of the basemat.
The subsections in this SE below discuss the staffs review of the effect of the changes to the layout and foundation interface for the Hermes 2 reactors and their relative position to Hermes 1 and Borings B-1, B-3, and B-6 as they relate to site geology (regional and local geology, and surface deformation) and geotechnical engineering (bearing capacity and settlements).
Regional and Local Geology
In PSAR Section 2.5.2, Kairos describes the proposed site as underlain by three distinct bedrock formations: the Mascot Dolomite, Murfreesboro Limestone, and Pond Springs Limestone Formations. Each of these formations (i.e., bedrock units) trends northeast to southwest parallel to the regional trend of the Appalachian Valley and Ridge Physiographic Province. The formations are, to some degree, calcareous as discussed in PSAR Section 2.5.2.
As discussed in PSAR Section 2.5.2.2 and Section 2.5.2.3, Kairos developed the subsurface stratigraphy from the geotechnical boring program at the site, as shown in PSAR Figure 2.5-23 and Figure 2.5-24. As discussed in Section 2.5.2.3, the geotechnical investigations of the proposed Hermes 2 site included soil borings and observation trenches, as well as laboratory testing.
PSAR Section 2.5.2.3.2 states that the site subsurface includes fill, alluvial soils, and residual soils above the bedrock units. PSAR Figure 2.5 2 and Figure 2.53 illustrate the subsurface geologic profiles for the Hermes 2 site. Kairos did not identify the specific geologic unit that will be the foundation-bearing layer for the Hermes 2 reactors. The need to confirm the foundation-bearing layer and associated geological and geophysical properties is further discussed below in SE Section, Bearing Capacity and Settlements.
The staff reviewed the changes between Hermes 1 and Hermes 2 for the Hermes 2 PSAR characterization of the regional and local geology at the proposed Hermes 2 site. Based on its review, the staff finds that the additional information provides an adequate description of the regional and local geology to sufficiently characterize the proposed site to support development of applicable design criteria for the Hermes 2 facility, and therefore, the staff finds that Kaiross geology characterization is acceptable.
Surface Deformation
PSAR Section 2.5.4 addresses subsurface deformation at the proposed site. With respect to surface faulting as a potential cause for subsurface deformation, Kairos stated that it will provide information on this topic in a Hermes 2 OL application.
PSAR Section 2.5.2.1 discusses indications of karst activity that Kairos discovered during the geotechnical investigations, at depth, at the proposed Hermes 2 site. Although the geotechnical investigations encountered evidence of karst activity at depth, Kairos indicates that there was no evidence of sinkhole activity encountered at the surface. Kairos also addresses karst in PSAR Section 2.5.4.3, in which Kairos state d that the Hermes 2 reactors foundation rock will be located at a depth at which no karstic dissolution is encountered. Kairos stated that the overburden soils and weathered rock will be removed to a depth of 30 ft. (9 meters (m)) and the exposed bedrock will be inspected (prior to the foundation preparation with either an engineered crushed stone or lean concrete fill) to ensure that the foundation rock has no evidence of karstic dissolution.
Based on the plant layout and foundation interface shown in Figure 2.5-11 and Figure 2.5-22, as well as the boring logs shown in Figure 2.5-22, the staff observed the presence of karst features such as voids and clay-filled solution features in Boring B-6 at depths near the planned foundation level. To confirm that the exposed bedrock does not show signs of karstic dissolution when the excavations are complete and before the foundation is prepared, and to provide reasonable assurance that regulatory requirements and license commitments are adequately addressed during the construction of the Hermes 2 facility, the staff recommends that the CPs include the following condition:
Kairos shall perform detailed geologic mapping of excavations for safety-related engineered structures; examine and evaluate geologic features discovered in those excavations, such as karst; and notify the Director of the Office of Nuclear Reactor Regulation, or the Directors designee, as specified in 10 CFR 50.4, once excavations for safety-related structures are open for examination by Staff.
Following receipt of notification from Kairos, the staff will determine whether direct examination of open excavations is necessary as part of the NRC construction inspection program.
The staff reviewed the new information characterizing the potential for surface deformation at the proposed Hermes 2 site. Because Kairos plans to remove the upper 30 ft. of overburden soils and weathered rock to ensure the foundation rock shows no evidence of karstic dissolution subject to the permit condition referenced above, the staff finds that the surface deformation is sufficiently characterized to support development of applicable design criteria for the Hermes 2 facility. Therefore, the staff finds that Kaiross characterization of surface deformation potential is acceptable.
Bearing Capacity and Settlements
Kairos discussed the stability of each reactors foundation at the proposed site in PSAR Section 2.5.5. Kairos stated that the foundation layout for the Hermes 2 reactors and their auxiliary facilities was selected based on the subsurface conditions determined from both historical documentation and subsurface borings at the proposed site. PSAR Figure 2.511 shows the proposed locations of the Hermes 2 reactors in the middle portion of the site, north of the Hermes 1 reactor location. PSAR Section 2.5.5.2 states that the bedrock interface is just above the depth of the reactor foundation at this site location, which provides an adequate bearing stratum.
The staff reviewed information in the PSAR regarding the bearing capacity and settlement of the proposed reactors. As illustrated in PSAR Figure 2.522, the safety-related portions of the Hermes 2 reactor buildings will be placed on a below-grade mat foundation on sound bedrock limestone. Kairos did not identify the specific rock unit(s) (i.e., Pond Springs Formation or Murfreesboro dolo mitic limestone) for foundation of each of the two reactors. Based on PSAR Figure 2.5-11, the bedrock beneath both reactors or only the northern reactor close to Boring B-6 could be in Pond Springs limestone, which is medium bedded and medium jointed.
Approximately, the top 5 ft. (1.5 m) of the Pond Springs limestone is weathered. It transitions quickly to fresh hard rock. The bedrock beneath the southern reactor close to Boring B-3 could be in the Murfreesboro dolomitic limestone, which is medium bedded and closely jointed with approximately 3 ft. (1 m) of weathering on top. Kairos did not observe any signs of sinkhole activity within the site but found karstic features, e.g., presence of solution cavities, as stated in PSAR Section 2.5.2.1. PSAR Section 2.5.5.2.1 states that additional details regarding characterization of the bedrock in the vicinity of the selected reactor location will be provided in a Hermes 2 OL application.
Boring B-6 encountered limestone at elevation 752.5 ft. Two clay-filled solution features and clay-filled fractures were observed below this elevation. The deeper clay-filled fracture extends at least to the elevation of 731 ft. (34.4 ft. below the grade), where the boring ended. The extent of this fracture below this elevation is currently unknown. A clay-filled fracture indicates that water flowed sometime in the past through the fracture and connection(s) with other karst feature(s) in this limestone stratum may exist. Because Boring B-3 did not extend into the limestone, the lateral extent of this karstic feature at the reactor location is currently unknown.
Additionally, it is not known if the subsurface limestone stratum at the reactor foundation locations contains any more karstic features and/or other clay-filled fractures.
Kairos stated in PSAR Section 2.5.4.3 that the foundation rock for the reactor will be at depths at which no evidence of karstic dissolution is encountered. Additionally, Kairos will over-excavate the zones (or areas) at which the bedrock is found to be compromised. Kairos further elaborated the process of selecting the foundation elevation of the reactors in PSAR Section 2.5.5.2. The foundation surface will be carefully examined and inspected for any weathered zones. If found, these weathered zones will be over-excavated and backfilled with concrete to develop a foundation adequate for the reactors. In addition, Kairos stated in PSAR Section 2.5.5.2 that a thin layer of concrete may be placed over the bedrock, if needed. The foundation of the safety-related structures will be mat foundation placed directly over sound bedrock or over this concrete layer. As shown in PSAR Figure 2.522, engineered backfill will be placed over the foundation bedrock to construct the non-safety related structures. Kairos will provide additional details on the bearing capacity and settlement of the foundation of the Hermes 2 reactors in addition to the lateral pressure in the OL application, as stated in PSAR Section 2.5.5.2.1.
As discussed in PSAR Section 2.5.5.2, since the reactors and the associated safety-related structures will be placed on bedrock or concrete, Kairos expects that the bearing capacity provided by the bedrock will be adequate. In addition, as noted above, Kairos stated in PSAR Section 2.5.4.3 that it will excavate and place the foundations at depths at which no karstic dissolution is present. Further, as noted in PSAR Section 2.5.5.2, any small, weathered zones in the exposed bedrock will be over-excavated and filled with concrete. If necessary, a small layer of concrete fill will be placed over the exposed bedrock and the foundation mat of the safety -
related structures will be placed over this concrete layer. The concrete layer is expected to increase the bearing capacity of the foundation and decrease the differential settlement. For these reasons, the staff finds that proposed foundation of both safety-related and non-safety-related structures will be able to provide adequate bearing capacity as the proposed mat foundation will be placed over sound rock and will have engineering enhancement if needed.
The staff also finds that the settlement of the reactor foundations will be limited only to immediate settlement because the foundation will be on rock or concrete, and therefore, the consolidation-related and secondary settlements will be negligible, if any.
As discussed in PSAR Section 2.5.5.2, the foundations of the safety-related and non-safety-related portions of the buildings are different. The safety-related portion will be placed on a concrete mat over the sound bedrock whereas the non-safety-related portion will have engineered fill over the bedrock to support the lighter portion of the structure. As a result, a differential settlement between the safety-related and the non-safety-related portions of the reactor buildings would be expected due to different stiffness properties of the engineered fill and the rock. As discussed in PSAR Section 3.5.1, Kairos will provide a moat in the design of the reactor buildings between the safety-related and the non-safety portions to accommodate the differential settlement in addition to displacement during design basis seismic events.
Based on the preceding discussion, the staff finds that Kairos adequately described the foundation of the proposed reactors and qualitatively discussed the expected bearing capacity and immediate settlement. The staff also finds that Kairos described adequately for the CP stage the subsurface geology that the reactor foundation is expected to encounter. As discussed, Kairos will provide detailed information on site characterization along with the calculations to demonstrate that adequate bearing capacity is available in a Hermes OL application.
Based on its review, the staff finds that the level of detail and analyses provided regarding Hermes 2 site geology, seismology, and geotechnical characteristics demonstrates an adequate design basis and satisfies the applicable acceptance criteria of NUREG 1537, Part 2, Section 2.5.
2.5.4 Conclusion
Based on staff findings above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the information regarding geology, seismology, and geotechnical characteristics in Hermes 2 PSAR Section 2.5 is sufficient and meets the applicable guidance and regulatory requirements identified in this SE section for the issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40.
2.6 Summary and Conclusions on Site Characteristics
The staff evaluated the descriptions and discussions of the proposed Hermes 2 site characteristics, as described in Chapter 2 of the Hermes 2 PSAR and finds that the information on Hermes 2 site characteristics: (1) provides reasonable assurance that the final design will conform to the design basis, (2) meets all applicable regulatory requirements, and (3) meets the applicable acceptance criteria in NUREG 1537, Part 2. Based on these findings and subject to the condition referenced above, the staff makes the following conclusions for the issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40:
- Kairos described the proposed design of the facility, including, but not limited to, the principal architectural and engineering criteria for the design, and has identified the major features or components incorporated therein for the protection of the health and safety of the public.
- Such further technical or design information as may be required to complete the safety analysis of the site characteristics, and which can reasonably be left for later consideration, will be supplied in the OL application.
- There is reasonable assurance that, taking into consideration the site criteria contained in 10 CFR Part 100, the proposed facility can be constructed and operated at the proposed location without undue risk to the health and safety of the public.
- The issuance of permits for the construction of the facility would not be inimical to the common defense and security or to the health and safety of the public.
2.7 References
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Washington, D.C. April 2020. ML20100F635.
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. Hermes Test Reactor Construction Permit No. CPTR-6, December 14, 2023, ML23338A258
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Pacific Earthquake Engineering Research Center (PEER). PEER 2018/08: Central and Eastern North America Ground Motion Characterization - NGA-East Final Report. PEER, University of California, Berkeley, CA. 2018.
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Tattelman, P. and I. Gringorten. Estimated Glaze Ice and Wind Loads at the Earths Surface for the Contiguous United States, Air Force Cambridge Research Laboratories, October 1973.
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Tennessee Valley Authority. Clinch River Nuclear Site Early Site Permit Application, Part 2, Site Safety Analysis Report, Revision 2. 2019. ML19030A358.
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. Elverton Quadrangle Map, TN, 2019, scale 1:24000.
https://ngmdb.usgs.gov/topoview/viewer/#14/35.9318/-84.4146, and https://ngmdb.usgs.gov/ht-bin/tv_browse.pl?id=7a5babe0555b6a16164330b30594bb3c. Accessed February 11, 2022.
THIS NRC STAFF DRAFT SE HAS BEEN PREPARED AND IS BEING RELEASED TO SUPPORT INTERACTIONS WITH THE ACRS. THIS DRAFT SE HAS NOT BEEN SUBJECT TO FULL NRC MANAGEMENT AND LEGAL REVIEWS AND APPROVALS, AND ITS CONTENTS SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITIONS.
3 DESIGN OF STRUCTURES, SYSTEMS, AND COMPONENTS
The purpose of the Hermes 2 test reactor facilitys structures, systems, and components (SSCs) is to ensure the safety of the facility and the health and safety of the public. The material presented in Chapter 3, Design of Structures, Systems, and Components, of the Hermes 2 preliminary safety analysis report (PSAR), Revision 1, discusses the safety and protective functions and related design features of the SSCs that help provide protection against uncontrolled releases of radioactive material and related exposures. The bases for the design criteria for some of the SSCs discussed in this chapter may be developed in other chapters of the PSAR.
This chapter of the Hermes 2 construction permit (CP) safety evaluation (SE) describes the U.S.
Nuclear Regulatory Commission (NRC) staffs (the staffs) technical review and evaluation of the preliminary design of the Hermes 2 SSCs as presented in Chapter 3 of the Hermes 2 PSAR.
The Hermes 2 CP application is for a test reactor facility whose purpose is to test and demonstrate the key technologies, design features, and safety functions of the Kairos Power fluoride salt-cooled high temperature reactor (KP-FHR) technology and its SSCs. The facility will also provide data and insights for the safety analysis tools and computational methodologies used for the design and licensing of a KP-FHR commercial power reactor. The Hermes 2 reactors will use tristructural isotropic (TRISO) fuel, molten salt as a coolant, graphite as a moderator, and transfer heat generated by the TRISO fuel to a power generation system (PGS) through a primary heat transfer system (PHTS) and intermediate heat transport system (IHTS).
In addition, each reactors decay heat removal system (DHRS) provides the safety-related heat removal function.
The staffs findings and conclusions in this SE are limited to whether the Hermes 2 facility satisfies the Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, requirements for the issuance of CPs. Each of the sections below identify the applicable principal design criteria (PDC) for the SSCs being evaluated.
3.1 Design Criteria
3.1.1 Introduction
The PDC for the facility SSCs are described in Section 3.1, Introduction, of the Hermes 2 PSAR. The PDC are based on the NRC-approved topical report (TR), KP-TR-003-NP-A, Principal Design Criteria for the Kairos Power Fluoride Salt-Cooled, High Temperature Reactor, Revision 1, dated May 22, 2020. Hermes 2 PSAR Table 3.1-2, Principal Design Criteria, identifies the PDC from KP-TR-003-NP-A that are applicable to the Hermes 2 facility and the PSAR sections that discuss how the PDC are met. In this section, the staff considered whether the four limitations and conditions identified in KP-TR-003-NP-A are satisfied. The staff evaluated the preliminary design information to determine whether the Hermes 2 design is consistent with the design aspects of the KP-FHR described in KP-TR-003-NP-A, and that any deviations from KP-TR-003-NP-A will lead to operation of the Hermes 2 facility without undue risk to the health and safety of the public.
3.1.2 Regulatory Evaluation
The staff reviewed Section 3.1.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facilities and the consistency of the design criteria between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 3.1.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 3.1.2 of the Hermes 1 SE.
3.1.3 Technical Evaluation
The staff reviewed Section 3.1 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 3.1, Introduction). The staff found that Section 3.1 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for a few significant changes which are evaluated below. The staff found that the following portions of Section 3.1 in the Hermes 2 PSAR contain information consistent with the Hermes 1 PSAR (e.g., minor or editorial changes only):
- Sections 3.1.1, Introduction, through 3.1.3, References
- Table 3.1-3, NRC Guidance Considered in the Design
Since the design and functionality of the Hermes 2 systems remain largely identical to those of Hermes 1, apart from the differences evaluated below, the design criteria in Section 3.1 of the Hermes 2 PSAR is consistent with the information in Section 3.1 of the Hermes 1 PSAR. Based on these consistencies, this section incorporates by reference Section 3.1.3 of the Hermes 1 SE except for the discussion of limitation and condition 1 from KP TR 003-NP-A.
3.1.3.1 Significant Changes Compared to the Hermes 1 PSAR
Hermes 2 is a two-unit facility that is capable of electrical power production while Hermes 1 is a single unit with no electrical power production capability. Therefore, the I HTS and PGS are unique to Hermes 2 and are described in Sections 5.2, Intermediate Heat Transport System, and 9.9, Power Generation System, of the Hermes 2 PSAR, respectively. The significant changes contained in Section 3.1 of the Hermes 2 PSAR, as compared to Section 3.1 of the Hermes 1 PSAR, include information regarding the following:
- In Table 3.1-1, Design Related 10 CFR Regulations Applicable to the Design, 10 CFR 20.1406, Minimization of Contamination, is identified as one regulation to be addressed by the IHTS and PGS design.
- In Table 3.1-2, Principal Design Criteria, PDC for the IHTS and PGS are identified.
- In Section 3.1.1 and Table 3.1-2, information is added stating that the two reactor units of Hermes 2 do not share safety-related SSCs and thus satisfy PDC 5.
The staff evaluated the sufficiency of this additional preliminary information regarding the Hermes 2 design criteria using the guidance and acceptance criteria in NUREG-1537, Part 2, Section 3.1, Design Criteria, 10 CFR 50.34(a)(3)(i) requirements on design criteria, and relevant guidance in Regulatory Guide 1.232, Guidance for Developing Principal Design Criteria for Non-light-water Reactors.
PSAR Table 3.1-1 identifies 10 CFR 20.1406 as a regulation to be addressed by the IHTS and PGS design. The staff evaluated how the IHTS and PGS designs address 10 CFR 20.1406 in Sections 5.2, Intermediate Heat Transport System, and 9.9, Power Generation System, of this SE. Based on the staffs evaluation in SE Sections 5.2 and 9.9, the staff finds that Kairos has appropriately identified 10 CFR 20.1406 as a regulation addressed by the IHTS and PGS design.
PSAR Table 3.1-2 identifies the PDC for the IHTS and PGS designs. The staff evaluated how the IHTS and PGS designs meet these PDCs in SE Sections 5.2, Intermediate Heat Transport System, and 9.9, Power Generation System. Based on the staffs evaluation in SE Sections 5.2 and 9.9, the staff finds that Kairos has appropriately identified the applicable PDCs for the IHTS and PGS based on their role and function within the overall Hermes 2 design.
PSAR Section 3.1.1 and Table 3.1-2 include additional information stating that the Hermes 2 reactors units satisfy PDC 5. PDC 5 states that safety significant SSCs shall not be shared among reactor units unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions. The staff evaluated the preliminary design information for Hermes 2 and confirmed that no safety-related SSCs are shared between the reactor units.
Therefore, the staff finds that the preliminary design for Hermes 2 is consistent with PDC 5.
Additionally, the staff evaluated the changes in Table 3.1-2, Principal Design Criteria, against the SE in KP TR 003-NP-A, Principal Design Criteria for the Kairos Power Fluoride Salt-Cooled, High Temperature Reactor, particularly the four limitations and conditions. The staff found that the findings from the Hermes 1 SE associated with limitations and conditions 2, 3, and 4 identified in the SE for KP TR 003 NP-A and the use of the terms safety related and postulated events remained applicable because the Hermes 2 PSAR had no relevant changes from the Hermes 1 PSAR in those areas. However, Hermes 2 has a key design feature that differs from Hermes 1 and is evaluated below for limitation and condition 1, which focuses on key design features for the KP-FHR.
Limitation and condition 1 states:
As presented in the TR, there are key design features without which the proposed PDC would not be applicable or encompass the full set of necessary design criteria.
Therefore, a KP FHR design referencing the TR must have the following:
- A chemically stable molten fluoride salt mixture coolant.
- TRISO fuel particles and fuel pebbles that, combined with other design features as applicable, demonstrate functional containment performance criteria consistent with SECY 18 0096 and applicable regulatory dose requirements.
- An intermediate coolant loop using a coolant that is compatible with reactor coolant, and that is demonstrated not to have a safety significant impact on the primary system.
- Near-atmospheric primary coolant pressures.
- The ability to ensure core cooling by maintaining coverage of the fuel within the reactor core with coolant.
If other key design features are identified by the applicant that could necessitate additional PDCs, those PDCs would be subject to the staffs review, independent of the TR.
For Hermes 2, the different key design feature from Hermes 1 is each unit contains an intermediate coolant loop (i.e., the IHTS) that is not present in the Hermes 1 design. All other key aspects of the Hermes 2 design, includingchemically stable molten fluoride salt, TRISO fuel particles and fuel pebbles, near-atmospheric primary coolant pressures, and the ability to maintain coolant coverage of the fuel and core cooling, are the same as Hermes 1 and consistent with the KP FHR design. Therefore, the PDCs associated with those items remain valid. Limitation and condition 1 from KP TR 003 NP-A states that a KP--FHR design must have
[a]n intermediate coolant loop using a coolant that is compatible with reactor coolant, and that is demonstrated not to have a safety significant impact on the primary system. In Section 5.1.3, System Evaluation, of the Hermes 2 PSAR, Kairos adds that the compatibility of the primary to intermediate coolant interaction will be address ed in the OL application. Similarly, in Section 1.3.9, Research and Development, of the Hermes 2 PSAR Kairos states that completing compatibility evaluations of the intermediate coolant and reactor coolant chemical interaction is a research and development item.
The staff evaluated this addition and Kaiross plan to address coolant compatibility in the OL application and found that it can be reasonably left for later consideration. Therefore, the staff finds that the information provided related to limitation and condition 1 is acceptable for a preliminary design. Consequently, the staff will confirm at the OL stage that limitation and condition 1 from KP-TR-003-NP-A is met by demonstrating compatibility between the primary and intermediate coolants and that the intermediate coolant does not have a safety significant impact on the primary system. Additional staff evaluation of intermediate coolant compatibility is provided in Sections 4.3, Reactor Vessel System, and 5.1, Primary Heat Transport System,
of this SE.
The staff concludes that the Hermes 2 PDC, as either approved in KP TR 003 NP-A or modified where necessary as described in the PSAR, are acceptable, consistent with the relevant acceptance criteria in NUREG-1537, Part 2, Section 3.1, Design Criteria, and meet the requirements in 10 CFR 50.34(a)(3)(i). Accordingly, the staff finds that the Hermes 2 design criteria provide reasonable assurance that the public will be protected from radiological risks that could result from operation of the reactor facility.
3.1.4 Conclusion
Based on staff findings above, and as incorporated by reference from the Hermes 1 SE, the staff concludes the information regarding the design criteria in Hermes 2 PSAR Section 3.1 is sufficient and meets the applicable guidance and regulatory requirements identified in this section for the issuance of CPs in accordance with 10 CFR 50.35, Issuance of construction permits, and 10 CFR 50.40, Common standards.
3.2 Meteorological Damage
3.2.1 Introduction
Section 3.2, Meteorological Damage, of the Hermes 2 PSAR describes the approach used to translate site meteorological parameters (e.g., normal wind speed, precipitation) into design loads used in the design of the safety-related portion of the reactor buildings. Section 3.2 of the Hermes 2 PSAR summarizes the methods for determining wind loads, including loads from hurricanes and tornadoes, and precipitation loads, including snow and ice loads. Relevant consensus design codes and design equations are identified, along with relevant NRC guidance.
3.2.2 Regulatory Evaluation
The staff reviewed Section 3.2.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facilities and the consistency of the design features for coping with meteorological damage between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 3.2.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 3.2.2 of the Hermes 1 SE.
3.2.3 Technical Evaluation
The staff reviewed Section 3.2 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 3.2, Meteorological Damage). The staff found that Section 3.2 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR. The staff also verified that the Hermes 2 meteorological design parameters and functionality of the safety-related portions of the reactor building remain identical to Hermes 1. Based on these consistencies, this section incorporates by reference Section 3.2.3, Technical Evaluation, of the Hermes 1 SE.
On the basis of its review, the staff finds a sufficient level of detail has been provided on the approach for determining meteorological design loads for the preliminary design of safety-related portions o f the reactor buildings and it satisfies the applicable acceptance criteria of NUREG 1537, Part 2, Section 3.2, Meteorological Damage. Accordingly, the staff finds that the design criteria and design for the protection from meteorological damage conditions are based on applicable local building codes, standards, and criteria that provides assurance that SSCs will continue to perform their safety functions as specified in the PSAR.
3.2.4 Conclusion
Based on the staff finding s above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the facility design features for coping with meteorological damage meet the applicable guidance and regulatory requirements identified in this section for issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further technical or design information required to complete the safety analysis may reasonably be left for later consideration. The staff will confirm that the final design conforms to this design basis during the evaluation of the Hermes 2 operating license (OL) application.
3.3 Water Damage
3.3.1 Introduction
Section 3.3, Water Damage, and Section 3.5.3.2, Conformance with PDC 2 for Internal and External Flooding, of the Hermes 2 PSAR describe the approach taken to establish loads on the safety-related portion of each reactor building due to postulated internal and external flooding events. Section 3.5.3.1, Conformance with PDC 2 for Meteorological Events, of the Hermes 2 PSAR states that the safety-related portions of the reactor buildings are designed in accordance with industry codes and standards, including the American Concrete Institute (ACI) 349 and the American Institute of Steel Construction (AISC) N690. Section 3.5.3.2 of the Hermes 2 PSAR states that the facility is a passively dry site and that the basemat of the safety-related portions of the structures are at grade level. Safety-related SSCs that are vulnerable to water damage from internal floods are elevated above the floors and water is directed away from SSCs via sloped floors and curbs.
3.3.2 Regulatory Evaluation
The staff reviewed Section 3.3.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facilities and the consistency of the approach taken regarding establishing loads from flooding events between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 3.3.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 3.3.2 of the Hermes 1 SE.
3.3.3 Technical Evaluation
The staff reviewed Section 3.3 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 3.3, Water Damage). The staff found that Section 3.3 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR. The staff also verified that the Hermes 2 approach taken regarding establishing loads from postulated internal and external flooding events on the safety-related portions of the reactor buildings remain identical to Hermes 1. Based on these consistencies, this section incorporates by reference Section 3.3.3, Technical Evaluation, of the Hermes 1 SE.
Based on its review, the staff finds that the level of detail provided on establishing design loads from postulated internal and external flooding events is adequate for the preliminary design and meets the applicable acceptance criteria of NUREG 1537, Part 2, Section 3.3, Water Damage.
The staff also finds that Kairos has adequately demonstrated that the safety-related portions of the reactor buildings are designed to withstand external flooding and are designed consistent with PDC 2 related to floods.
3.3.4 Conclusion
Based on the findings above, and as incorporated by reference from Hermes 1 SE, the staff concludes that the facility design features for coping with water damage meet the applicable guidance and regulatory requirements identified in this section for issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further technical or design information required to complete the safety analysis may reasonably be left for later consideration. The staff will confirm that the final design conforms to this design basis during the evaluation of the Hermes 2 OL application.
3.4 Seismic Damage
3.4.1 Introduction
Section 3.4, Seismic Damage, of the Hermes 2 PSAR describes the design of SSCs that are required to remain functional in the event of an earthquake. Section 3.4 states that Kairos followed the graded approach of American Society of Civil Engineers (ASCE) 43 19, Seismic Design Criteria for Structures, Systems and Components in Nuclear Facilities, for the seismic design of Hermes 2. The safety-related SSCs were identified by Kairos as Seismic Design Category (SDC) 3, consistent with ASCE 43 19, and the design response spectra were developed based on this category. PSAR Section 3.4 also discusses how the structure was modeled and how the response analysis was performed.
3.4.2 Regulatory Evaluation
The staff reviewed Section 3.4.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facilities and the consistency of the design features for the protection against seismic damage between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 3.4.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 3.4.2 of the Hermes 1 SE.
3.4.3 Technical Evaluation
The staff reviewed Section 3.4 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 3.4, Seismic Damage). The staff found that Section 3.4 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for editorial changes. The staff also verified that the Hermes 2 seismic design bases and methodology, as well as the functionality of the safety-related SSCs and non-safety related SSCs, remain identical to Hermes 1. Based on these consistencies, this section incorporates by reference Section 3.4.3, Technical Evaluation, of the Hermes 1 SE.
Based on its review, the staff finds that the level of detail provided on seismic design bases and methodology for seismic damage of SSCs is adequate for the preliminary design and supports the applicable acceptance criteria of NUREG 1537, Part 2, Section 3.4, Seismic Damage.
3.4.4 Conclusion
Based on the staff finding s above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the facility seismic design meets the applicable guidance and regulatory requirements identified in this section for issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further technical or design information required to complete the safety analysis may reasonably be left for later consideration. The staff will confirm that the final design conforms to this design basis during the evaluation of the Hermes 2 OL application.
3.5 Plant Structures
3.5.1 Introduction
Section 3.5, Plant Structures, of the Hermes 2 PSAR describes the principal structural elements and general design of the reactor buildings, which also includes the primary and secondary biological shield structures as described in PSAR Section 4.4, Biological Shield.
PSAR Section 3.5 states that the reactor buildings are the only structures on the site that serve a safety function and that the structures are separated into safety-related and non-safety related portions by a seismic moat. The safety-related portion of the reactor buildings is supported by a seismic base isolation system. This section of the PSAR also lists the safety functions of the reactor buildings and the applicable PDC, which are 1, 2, 3, 4, 75, and 76. The PSAR summarizes how the design is consistent with these criteria and provides additional detail on how the reactor buildings meet PDC 2. Much of this information supports or repeats information contained in earlier PSAR sections, specifically Sections 3.2, 3.3, and 3.4.
3.5.2 Regulatory Evaluation
The staff reviewed Section 3.5.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facilities and the consistency of the plant structures between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 3.5.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 3.5.2 of the Hermes 1 SE.
3.5.3 Technical Evaluation
The staff reviewed Section 3.5 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 3.5, Plant Structures). The staff found that Section 3.5 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for two minor changes and one significant change, which are evaluated below in SE Sections 3.5.3.1 and 3.5.3.2, respectively. The staff found that the following portions of Section 3.5 in the Hermes 2 PSAR contain information consistent with the Hermes 1 PSAR (e.g., minor or editorial changes only):
- Sections 3.5.1, Description of Plant Structures, 3.5.4, Testing and Inspections, and 3.5.5, References
- Sections 3.5.3.1, Conformance with PDC 2 for Meteorological Events, 3.5.3.2, Conformance with PDC 2 for Internal and External Flooding, 3.5.3.3, Conformance with PDC 2 for Earthquakes, and 3.5.3.4, Conformance with PDC 2 for Other Hazards
Since the design and functionality of the Hermes 2 systems remain largely identical to those of Hermes 1, apart from the differences evaluated below, the description of plant structures in Section 3.5 of the Hermes 2 PSAR is consistent with the information in Section 3.5 of the Hermes 1 PSAR. Based on these consistencies, this section incorporates by reference Section 3.5.3, Technical Evaluation, of the Hermes 1 SE.
3.5.3.1 Minor Changes Compared to the Hermes 1 PSAR
The minor changes in Hermes 2 PSAR Section 3.5, as compared to the information in Hermes 1 PSAR Section 3.5, include the following:
- Figure 3.5-1 Schematic of the Reactor Building in the Hermes 2 PSAR was revised.
- In Section 3.5.3.2.1, External Flood Design Features, Kairos clarified that no safety-related SSCs would be located below the basemat elevation of the safety-related portion of the reactor buildings.
In Hermes 2 PSAR Section 3.5, Figure 3.5-1 was revised. The revised f igure is a mirror image of the Hermes 1 PSAR Figure 3.5-1 with a change in the orientation of the Spent Fuel Storage in the Pebble Handling and Storage System cell and the arrangement of equipment in the reactor cell. The overall dimensions and general arrangement of the Hermes 2 reactor buildings remain essentially identical to that of Hermes 1; therefore, the change has no significant impact on the structural design methodology.
Additionally, in Section 3.5.3.2.1, Kairos included a clarification in the following sentence (emphasis added) :
The basemat of the safety-related portion of the reactor building, which is supported by the base isolators, as discussed in Section 3.5.1, is at grade level and there are no safety-related SSCs in the safety-related portion of the reactor building located below the basemat elevation that are classified as safety-related for flooding events.
The staff finds that the change provides completeness and clarity in describing that there are no SSCs classified as safety-related for flooding events that are located below the basemat elevation of the safety-related portion of the reactor buildings (see PSAR Figure 3.5-1). The staff finds that the change is minor and involves no technical change to the Hermes 2 PSAR. Based on the above, the staff finds that the two minor changes are acceptable.
3.5. 3.2 Significant Changes Compared to the Hermes 1 PSAR
A significant change contained in Section 3.5 of the Hermes 2 PSAR, as compared to Section 3.5 of the Hermes 1 PSAR, includes information regarding the following:
- Addition of PDC 4 to the design bases of the reactor building such that it is protected from and provides protection for other safety-related SSCs against environmental and dynamic effects associated with high-pressure steam system pipe leaks and breaks.
The staff review determined that outside of this addition, the remaining portion of Hermes 2 PSAR Sections 3.5.2 and 3.5.3, System Evaluation, contains information consistent with the Hermes 1 PSAR. This addition is a conforming change consistent with the design bases in PSAR Section 9.9.1.1, Design Bases, which includes PDC 4 to protect nearby safety-related systems against dynamic effects of high-pressure steam system pipe leaks related to the new Hermes 2 steam system described in the new Section 9.9.1, Steam System, of the Hermes 2 PSAR. The steam system is one of several subsystems that make up the PGS. The staff evaluated the sufficiency of this additional preliminary information related to compliance with PDC 4 below.
PDC 4
PDC 4 states, in part, that:
SSCs which are safety significant shall be designed to accommodate the effects of and be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. These SSCs shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit.
Section 3.5.3, System Evaluation, of the Hermes 2 PSAR states that the safety-related portion of the reactor buildings is designed so they will be able to perform their physical protection safety function described in PSAR Section 3.5.1 under the environmental and dynamic effects associated with high-pressure steam system pipe leaks and breaks, including if the non-safety related portion of the reactor buildings is damaged due to such effects. Further, PSAR Section 9.9.1.2, System Evaluation, for the steam system states that safety-related SSCs located inside the safety-related portion of each reactor building are protected from the dynamic effects associated with high-pressure steam line breaks by either protective design features (e.g.,
barriers or blowout panels), are designed for the environmental conditions, are located sufficiently far enough away to avoid the hazards, or a combination of these measures.
The staff finds that the preliminary design basis of the safety-related portion of the Hermes 2 reactor buildings is consistent with PDC 4 because: (a) the safety-related portion of the reactor building will be designed to remain capable of performing its safety functions of protecting safety-related SSCs under the environmental conditions and dynamic effects associated with high-pressure steam system pipe leaks and breaks postulated to occur (i) outside the safety-related portion of the reactor building (i.e., in the non-safety related portion of the structure); and ( ii) inside the safety-related portion of the reactor building structure; (b) the proposed design codes in the PSAR for the safety-related portion of the reactor building, namely ACI 349 and ANSI/AISC N690, include structural design provisions for impulsive and impactive load effects; and (c) the staff will verify that the reactor building final design conforms to PDC 4 during the Hermes 2 OL application review.
Based on its review, the staff finds that the level of detail provided on the general design of the reactor buildings is adequate for the preliminary design and the information provided adequately demonstrates that the structural design of the reactor buildings is consistent with PDCs 1, 2, 3, 4, 75, and 76.
3.5.4 Conclusion
Based on the staff finding s above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the general reactor building design meets the applicable guidance and regulatory requirements identified in this section for issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further technical or design details required to complete the safety analysis may reasonably be left for later consideration and the staff will confirm that the final design conforms to this design basis during the evaluation of the Hermes 2 OL application.
3.6 Systems and Components
3.6.1 Introduction
Section 3.6, Systems and Components, of the Hermes 2 PSAR describes the design bases for the systems and components required to function for safe reactor operation and shutdown.
PSAR Section 3.6.1, General Design Basis Information, describes the safety functions performed by safety-related SSCs and PSAR Section 3.6.2, Classification of Structures, Systems, and Components, describes how SSCs are classified.
PSAR Section 3.6.1 identifies three fundamental safety functions provided by Hermes 2 SSCs:
(1) prevent uncontrolled releases of radionuclides, (2) remove decay heat in a postulated event, and (3) control reactivity in the reactor core. The primary SSCs credited for preventing an uncontrolled radionuclide release are the reactor fuel, reactor vessel, reactor coolant, and reactor protection system. The SSCs used to ensure decay heat removal are the decay heat removal system with support from the reactor vessel, the reactor vessel support system, and the reactor protection system. The primary means of reactivity control is provided by the reactivity control and shutdown system and the reactor protection system with support from reactor vessel and nuclear design. The staff determined that the reactor buildings are designed to provide the necessary protection from external events for all of these SSCs. The staff evaluation of the reactor buildings is documented in SE Section 3.5.
3.6.2 Regulatory Evaluation
The staff reviewed Section 3.6.2, Regulatory Evaluation, of the Hermes 1 SE for applicability to the Hermes 2 SE. Based on the similarities between the Hermes 1 and Hermes 2 facilities and the consistency of the design of the systems and components between Hermes 1 and Hermes 2, the staff finds that the regulations and guidance listed in Section 3.6.2 of the Hermes 1 SE are applicable to Hermes 2. Therefore, this section incorporates by reference Section 3.6.2 of the Hermes 1 SE.
3.6.3 Technical Evaluation
The staff reviewed Section 3.6 of the Hermes 2 PSAR and compared it to the equivalent section in the Hermes 1 PSAR (Section 3.6, Systems and Components). The staff found that Section 3.6 of the Hermes 2 PSAR contains information consistent with that in the Hermes 1 PSAR, except for one minor and a few significant changes, which are evaluated below in SE Sections 3.6.3.1 and 3.6.3.2, respectively. The staff found that the following portions of Section 3.6 in the Hermes 2 PSAR contain information consistent with the Hermes 1 PSAR (e.g., minor or editorial changes only):
- Sections 3.6.1 and 3.6.2
- Table 3.6-2, Design and Construction Codes and Standards for Fluid Systems
Since the design and functionality of the Hermes 2 systems remain largely identical to those of Hermes 1, apart from the differences evaluated below, the systems and components in Section 3.6 of the Hermes 2 PSAR are consistent with the information in Section 3.6 of the Hermes 1 PSAR. Based on these consistencies, this section incorporates by reference Section 3.6.3, Technical Evaluation, of the Hermes 1 SE.
3.6.3.1 Minor Changes Compared to the Hermes 1 PSAR
The minor change in Hermes 2 PSAR Section 3.6, as compared to the information in Hermes 1 PSAR Section 3.6, includes the following:
- Section 3.6.1.1 notes that the reactor protection system (RPS) also stops the intermediate salt pump (ISP) to ensure Flibe level remains constant during postulated events.
The ISP is a new component in the Hermes 2 design. Hermes 1 does not contain an ISP because it does not have an IHTS. The staff finds that the new ISP trip is appropriate, because it reduces the chance of overcooling of the PHTS following an RPS actuation as described in Section 7.3.1, Reactor Protection System, of the Hermes 2 PSAR. Therefore, the new ISP trip upon RPS actuation is acceptable.
3.6.3.2 Significant Changes Compared to the Hermes 1 PSAR
Significant changes contained in Section 3.6 of the Hermes 2 PSAR, as compared to Section 3.6 of the Hermes 1 PSAR, include the information regarding the following:
- The following IHTS SSCs were added to Table 3.6-1, Structures, Systems, and Components: intermediate heat exchanger (IHX), ISPs, intermediate piping, superheater, intermediate loop auxiliary heating subsystem, intermediate inert gas subsystem, intermediate coolant inventory management subsystem, intermediate coolant chemistry control subsystem, intermediate coolant.
- The following PGS SSCs were added to Table 3.6-1: turbine generator system, steam system, condensate and feedwater system.
Hermes 2 is a two-unit facility that is capable of producing electrical power while Hermes 1 is a single unit facility with no electrical power production capability. Therefore, the IHTS and PGS are unique to Hermes 2 and are described in Sections 5.2 and 9.9 of Hermes 2 PSAR, respectively. The additional components related to the IHTS and PGS are added to Table 3.6-1, which summarizes the safety, seismic, and quality classification of the SSCs.
The staff evaluated the sufficiency of this additional preliminary information regarding the Hermes 2 SSCs using the guidance and acceptance criteria in Section 3.5, Systems and Components, of NUREG-1537 Part 2, 10 CFR 50.2, and Regulatory Guide (RG) 1.29, Seismic Design Classification for Nuclear Power Plants. Like Hermes 1, Hermes 2 uses the definition of 10 CFR 50.2 for safety-related SSCs to establish those SSCs that are classified as safety-related, with the exception of integrity of the reactor coolant pressure boundary, which has been modified to say integrity of the portions of the reactor coolant boundary relied upon to maintain coolant level above the active core.
The IHTS and PGS components are classified as non-safety related, except for the rupture disks in the intermediate inert gas subsystems. The rupture disks are used to prevent overpressure in the IHTS during a postulated superheater tube leak or rupture event. The rupture disk standpipes and vent lines would also provide a relief path for the steam from a superheater tube rupture to prevent the steam from reaching the IHX. While the IHX, including the IHX tubes, are classified as non-safety related, the staff noted that failure of one or more IHX tubes following a superheater tube rupture could lead to unanalyzed conditions due to potential Flibe-water interactions or higher than assumed levels of BeNaF ingress into the PHTS.
Recognizing the preliminary nature of the Hermes 2 design and that Kairos has not requested final approval of the safety of any design feature or specification in its application, the staff was unable to confirm that the IHX complies with the Hermes 2 definition of safety-related SSCs.
To resolve this issue, Kairos confirmed in RCI 1 (ML24103A241) that the final design for Hermes 2 will demonstrate that the IHX tubes will not need to be classified as a safety-related SSC. Or, if the IHX tubes are relied upon to remain functional during and after a postulated event, Kairos will demonstrate that their failure is not credible considering all relevant factors.
Based on the information identified in RCI 1 to be provided in the OL application, the staff finds that the classification for the IHTS and PGS components complies with Kaiross modified 10 CFR 50.2 definition, with the exception of the IHX for which the safety classification will be assessed as part of the OL application review.
RG 1.29 describes a method that the staff considers acceptable for the seismic classification of the SSCs for light water reactors (LWRs). While RG 1.29 is applicable to LWRs, it provides guidance related to the SSCs that should be designed in accordance with seismic design criteria that can also be useful for non-LWRs like Hermes 2. Based on the guidance from RG 1.29, the use of the local building code for the seismic design criteria of the non-safety related IHTS and PGS components is acceptable since they do not perform the safety functions to prevent uncontrolled release of radionuclides, remove decay heat during a postulated event, or control reactivity in the core. The staff also finds that it is appropriate to designate the non-safety related IHTS and PGS components as not quality-related. Table 3.6-1 of Hermes 2 PSAR shows that the rupture disks in the intermediate inert gas subsystems will be seismically designed to local building codes with the quality classification of quality-related. The staff finds these classifications appropriate because the rupture disks are safety -related components that are not relied upon to remain functional following a seismic event.
Based on its review, the staff finds that the level of detail provided regarding design bases for the systems and components that are required to function at the Hermes 2 facility is adequate for the preliminary design and supports the applicable acceptance criteria of NUREG 1537, Part 2, Section 3.5, Systems and Components. Therefore, the staff finds that the design bases of the systems and components provide reasonable assurance that the facility systems and components will function as designed to ensure safe operation and safe shutdown of the reactors.
3.6.4 Conclusion
Based on the staff finding s above, and as incorporated by reference from the Hermes 1 SE, the staff concludes that the Hermes 2 facility systems and components meet the applicable guidance and regulatory requirements identified in this section for issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40. Further technical or design information required to complete the safety analysis may reasonably be left for later consideration. The staff will confirm that the final design conforms to this design basis during the review of the Hermes 2 OL application.
3.7 Summary and Conclusions on Design of Structures, Systems, and Components
The staff evaluated the information in Chapter 3 of the PSAR regarding the design of SSCs for Hermes 2 and finds that the preliminary information on, and design criteria of, the SSCs, including the PDC, design bases, and information relating to materials of construction, general arrangement, and approximate dimensions: (1) provide reasonable assurance that the final design will conform to the design bases, (2) meet all applicable regulatory requirements, and (3) meet the applicable acceptance criteria in NUREG 1537, Part 2. Based on these findings, the staff makes the following conclusions regarding issuance of CPs in accordance with 10 CFR 50.35 and 10 CFR 50.40:
- Kairos has described the proposed design of the SSCs, including, but not limited to, the principal architectural and engineering criteria for the design, and has identified the major features or components incorporated therein for the protection of the health and safety of the public.
- Such further technical or design information required to complete the safety analysis of the Hermes 2 SSCs, and which can reasonably be left for later consideration, will be provided in the final safety analysis report as part of the OL application.
- There is reasonable assurance: (i) that the construction of the facility will not endanger the health and safety of the public, and (ii) that construction activities can be conducted in compliance with the Commissions regulations.
- The issuance of a permit for the construction of the facility would not be inimical to the common defense and security or to the health and safety of the public.
3.8 References
Kairos Power LLC. KP TR 003 NP A, "Principal Design Criteria for the Kairos Power Fluoride Salt-Cooled, High Temperature Reactor," Revision 1, June 2020, ML20167A174.
. Submittal of the Preliminary Safety Analysis Report for the Hermes 2 Kairos Power Fluoride Salt-Cooled, High Temperature Non-Power Reactor (Hermes 2), Revision 1, [Month]
xx, 2024, Pkg. MLxxxxxxxxx.
U.S. Nuclear Regulatory Commission, Safety Evaluation Related to the Kairo Power LLC Construction Permit Application for the Hermes Test Reactor, Docket 50- 7513, June 13, 2023.
. Hermes 2 General Audit summary report. 2024, MLXXXXXXXXX
. Regulatory Guide 1.29, Seismic Design Classification for Nuclear Power Plants, Revision 6, July 2022, ML21155A003