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Kairos Power, LLC - Presentation Slides for the May 16, 2024, ACRS Kairos Power Subcommittee Meeting (Non-Proprietary)
	ML24150A245
Person / Time
Site:	Hermes File:Kairos Power icon.png
Issue date:	05/29/2024
From:	; Kairos Power
To:	; Office of Nuclear Reactor Regulation
Shared Package
ML24150A243	List: ML24150A244; ML24150A245;
References
	KP-NRC-2405-010
	Download: ML24150A245 (1)
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KP-NRC-2405-010 Presentation Slides for the May 16, 2024 ACRS Kairos Power Subcommittee Meeting (Non-Proprietary)

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HERMES 2 PSAR (CH. 2, 3, 5, 9, 13)

MARTIN BRYAN - SENIOR MANAGER, SITE LICENSING DREW PEEBLES - SENIOR MANAGER, SAFETY LICENSING JUNE 4, 2024 ACRS Kairos Power Subcommittee Meeting 1

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Kairos Powers mission is to enable the worlds transition to clean energy, with the ultimate goal of dramatically improving peoples quality of life while protecting the environment.

In order to achieve this mission, we must prioritize our efforts to focus on a clean energy technology that is affordable and safe.

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Agenda

Chapter 5:

Heat Transport Systems

Chapter 13:

Accident Analysis

Chapter 9:

Auxiliary Systems

Chapter 2:

Site Characteristics

Chapter 3:

Design of Structures, Systems, and Components 3

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Hermes 2 PSAR Chapter 5: Heat Transport Systems

Primary Heat Transport System The primary heat transport system (PHTS) is responsible for transporting heat from the reactor to the intermediate heat transport system (IHTS) during power operation The reactor coolant is circulated through an intermediate heat exchanger (IHX) rather than a heat rejection radiator A heat rejection radiator (HRR) is included in the PHTS for low power startup and normal shutdown conditions The HRR is not used during power operation 4

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Hermes 2 PSAR Chapter 5: Heat Transport Systems (cont.)

5 Primary Salt Pump Reactor Intermediate Heat Exchanger Primary Heat Transport System (Unit-Specific)

Intermediate Heat Transport System (Unit-Specific)

From Unit-Specific IHTS to Shared Power Generation System Heat Rejection Radiator (Normally Off)

Air Intermediate Salt Pump Intermediate Salt Pump Intermediate Salt Vessel Intermediate Salt Vessel Steam Superheater

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Hermes 2 PSAR Chapter 5: Heat Transport Systems (cont.)

The IHTS is responsible for transporting heat from the PHTS to the power generation system (PGS) during power operation Intermediate coolant, or (BeNaF) is a mixture of sodium fluoride and beryllium fluoride BeNaF is chemically compatible with Flibe Intermediate salt pumps circulate BeNaF between the IHX and the superheaters which interface with the power generation system

The IHTS operates near atmospheric pressure and does not provide a safety-related heat removal function 6

Value Parameter 35 MWth Thermal duty 580 - 615°C IHTS hot leg temperature 490 - 525°C IHTS cold leg temperature 140 - 250 kg/s Nominal flow rate Near ambient pressure IHTS design pressure Intermediate coolant pressure is maintained below primary coolant pressure within the IHX Intermediate piping, coolant, and components (other than the rupture disks) are all non-safety related

The IHTS has safety-related rupture disks that relieve pressure in the event of a superheater tube leak or rupture and provide a relief path for the steam.

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Hermes 2 PSAR Chapter 5: Heat Transport Systems (cont.)

Failure of the IHTS components during seismic events does not preclude safety-related SSCs from performing their function. (PDC 2)

The IHTS is designed to facilitate tritium capture in the intermediate inert gas system via the tritium management system. (PDC 60)

The cover gas space in the intermediate salt vessels is monitored for radioactivity to support the evaluation of the radioactive material releases that might occur as a result of a system failure. (PDC 64)

BeNaF is chemically compatible with Flibe, thus only one passive barrier between the salts (the IHX) is required. The IHX and the superheater provide two passive barriers between the Flibe and steam. Additionally, the design of the IHTS provides a relief path for steam from a superheater tube rupture and prevents the steam from entering the piping connecting the ISVs to the IHX. (PDC 73)

The IHTS will be designed according to 10 CFR 20.1406, to the extent practicable, to minimize contamination and support eventual decommissioning.

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PSAR Chapter 13: Accident Analysis

Hermes 2 uses the same Maximum Hypothetical Accident (MHA) as described in the Hermes PSAR.

The MHA and postulated events presented in Chapter 13 apply to each unit and are evaluated against the siting criteria for each unit separately. This is consistent with the requirements in 10 CFR 100.11(b) for multiple reactor facilities where the reactors are independent to the extent that a postulated event for one unit does not affect the safety of operation of the other unit.

10 CFR 100.11(b)(1-2):

For sites for multiple reactor facilities consideration should be given to the following:(1) If the reactors are independent to the extent that an accident in one reactor would not initiate an accident in another, the size of the exclusion area, low population zone and population center distance shall be fulfilled with respect to each reactor individually. The envelopes of the plan overlay of the areas so calculated shall then be taken as their respective boundaries.

(2) If the reactors are interconnected to the extent that an accident in one reactor could affect the safety of operation of any other, the size of the exclusion area, low population zone and population center distance shall be based upon the assumption that all interconnected reactors emit their postulated fission product releases simultaneously. This requirement may be reduced in relation to the degree of coupling between reactors, the probability of concomitant accidents and the probability that an individual would not be exposed to the radiation effects from simultaneous releases. The applicant would be expected to justify to the satisfaction of the Commission the basis for such a reduction in the source term.

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PSAR Chapter 13: Accident Analysis

Potential hazards and initiating events associated with the intermediate coolant, intermediate heat transport system, and power generation system are addressed in Chapter 13.

New initiators for increase in heat removal events include intermediate salt pump overspeed, spurious opening of a turbine bypass valve or steam safety valve, superheater shell leak, steam line break, and spurious actuation of the heat rejection radiator New events grouped under the salt spill postulated event include leaks from the IHTS and IHX tube break or leak New initiators for loss of normal heat sink events include intermediate salt pump failure and superheater tube rupture New systems included in the radioactive release from subsystem or component postulated event include the IHTS and power generation system Faults in the IHTS are included within the general challenges to normal operation postulated event group New internal hazard events include turbine missile and high energy steam line break, though potential impact of these hazards on safety-related functions are precluded by design and location of the power generation system Gross IHX failure due to superheater tube rupture or leak is added to the prevented events (Section 13.1.10) 9

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Questions

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PSAR Chapter 9: Auxiliary Systems

Reactor Coolant Auxiliary Systems Design of Chemistry control system, inert gas system, inventory management system and reactor thermal management systems for Hermes 2 are all identical to those systems in Hermes The Hermes 2 tritium management system includes two additional tritium functions to cover Hermes 2-specific systems:

Tritium capture from IHTS cover gas A small amount of HF is added to the IHTS to convert tritium to TF. Tritium that then evolves to the IHTS cover gas is pulled from the intermediate salt vessels of the IHTS, sent through a tritium conversion bed, and captured using a tritium capture bed Tritium capture from heat rejection radiator enclosure During normal power operations, HRR is not operating - tritium captured from the heat rejection radiator enclosure.

Air in enclosure is sent through a tritium conversion bed and ultimately to a tritium capture bed During low-power startup and normal shutdown, HRR is operating as heat rejection pathway - tritium discharged as a gaseous effluent.

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PSAR Chapter 9: Auxiliary Systems (cont.)

Reactor Building Heating, Ventilation, and Air Conditioning; Pebble-Handling and Storage System; and Possession and Use of Byproduct, Source, and Special Nuclear Material All content for these sections in the Hermes 2 PSAR is identical to the Hermes PSAR apart from some additional clarification information added to the fuel storage and special nuclear material sections.

Other non-safety related auxiliary systems for Hermes 2 will have the same functions as those systems in Hermes. However, these systems (listed below) will be shared between the Hermes 2 units.

Fire Protection Systems and Programs Communication Systems Service Water System Treated Water System Auxiliary Site Services Power Generation System 12

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PSAR Chapter 9: Auxiliary Systems (cont.)

Power Generation System No safety functions are performed by SSCs in power generation system The majority of this system is shared between both units Power Generation System includes a steam system, turbine generator system, and condensate and feedwater system:

The steam system uses heat from the IHTS to superheat steam for the turbine generator system The turbine generator system converts energy in the steam to electrical power.

The condensate and feedwater system returns condensed steam from the air-cooled condenser to the condensate tank, deaerates and reheats the water to feedwater temperature and pressure, and supplies feedwater to the evaporator 13

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PSAR Chapter 9: Auxiliary Systems (cont.)

Power Generation System Design Basis The power generation system piping is not located near safety-related SSCs. Safety-related SSCs located inside the safety-related portion of the Reactor Building are protected from the dynamic effects associated with high-pressure steam line breaks by design. The turbine generator is favorably oriented with respect to the Reactor Buildings. The turbine generator is designed to preclude overspeed (PDC 4)

Tritium accumulation in the steam system and the condensate and feedwater system is controlled by collecting liquid discharge in a flash vessel, evaporating the liquid, and releasing the gaseous effluent.

(PDC 60)

The radioactivity levels are monitored in the steam and vapor vents to support the evaluation of the radioactive material releases that might occur as a result of a system failure (PDC 64)

Consistent with 10 CFR 20.1406, the power generation system is designed, to the extent practicable, to minimize contamination of the facility and the environment, and facilitate eventual decommissioning 14

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Questions

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PSAR Chapter 2: Site Characteristics

Geography and Demography The Hermes 2 site is identical to the Hermes site, but the approximate facility coordinates are roughly 400 ft North.

The Hermes 2 demographical analysis uses 2020 census data. The population projections are also extended to 2040 in consideration of the longer life of the Hermes 2 facility.

Nearby Industrial, Transportation, and Military Installations The Hermes 2 application includes additional nearby facilities, including the Hermes facility and the TRISO-X fuel fabrication facility.

The effects of hazards from these additional nearby facilities will be evaluated in the application for an Operating License.

The effective area used in potential aircraft impact calculations was doubled to account for the safety-related areas in each reactor building.

No additional exceedances of any DOE-STD-3014-2006 screening criteria and therefore no changes to the design requirements of the safety-related portions of the Reactor Buildings.

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PSAR Chapter 2: Site Characteristics (cont.)

Meteorology Minor updates to meteorological data including data made available from 2020 to 2022.

Historical meteorological studies from 1953 and 2011 indicate that basic flow patterns have been in place during the recorded weather history of the Oak Ridge Reservation area No design impacts from data updates

Hydrology No change

Geology, Seismology, and Geotechnical Characteristics Previous geotechnical borings completed to support Hermes, and their subsequent analysis, are used for the geological characterization for Hermes 2.

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PSAR Chapter 3:

Design of Structures, Systems, and Components

The intermediate heat transport system (IHTS) and power generation system (PGS) are included in the lists of applicable 10 CFR Regulations, Principal Design Criteria and Structures, Systems, and Components PDC 5 applicable due to the presence of multiple units, and satisfied because no safety-related SSCs are shared between units.

PDC 73 applicable because the reactor coolant interfaces with an intermediate fluid. Discussion of evaluation in Ch. 5.

Seismic design of safety-related IHTS rupture disks will be to local building code, consistent with the design rules for the IHTS

The design considerations from meteorological, water, and seismic damage for Hermes 2 are identical to those for Hermes

Plant Structural Design The Hermes 2 reactor building design requirements are almost identical to the Hermes reactor building.

However, the Hermes 2 building must consider any hazards posed by the power generation system. So, PDC 4 is included in the reactor building design basis 18

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