ML23285A164

Official Exhibit - NRC-010-MA-CM01 - Staff Presentation Slides - Safety Panel (October 12, 2023)

ML23285A164
Person / Time
Site:	Hermes
Issue date:	10/12/2023
From:	NRC/OGC
To:	NRC/OCM
SECY RAS
References
Construction Permit Mndtry Hrg, RAS 56826, 50-7513-CP
Download: ML23285A164 (0)

Text

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of KAIROS POWER LLC Docket No. 50-7513-CP (Hermes Test Reactor)

Hearing Exhibit Exhibit Number: NRC-010 Exhibit

Title:

Staff Presentation Slides - Safety Panel (October 12, 2023)

NRC Staff Exhibit NRC-010 KAIROS HERMES MANDATORY HEARING CONSTRUCTION PERMIT APPLICATION REVIEW Safety Panel 1

William Jessup B r a n c h C h i e f, N R R / D A N U 2

PANELISTS William Jessup

• Chief, Advanced Reactor Licensing Branch 1, NRR/DANU Edward Helvenston

• Project Manager, NRR/DANU Chris Van Wert

• Senior Technical Advisor for Reactor Fuel, NRR/DSS Alexander Chereskin

• Materials Engineer, NRR/DANU Michelle Hart

• Senior Reactor Engineer, NRR/DANU Alexandra Siwy

• Senior Nuclear Engineer, NRR/DANU 3

INTRODUCTION TO SAFETY REVIEW Hermes would be Licensing process licensed as a testing similar to that for facility under 10 CFR other non-power Part Part 50 50 facilities Novel technical issues 4

REVIEW PROCESS AND APPROACH Standard review plan for non-power NUREG-1537 Guidance reactors Focused on matters that are most safety Risk-Informed Review significant Integrated review led by staff with advanced Core Team Approach reactor expertise 5

Edward Helvenston P r o j e c t M a n a g e r, N R R / D A N U 6

PERMIT CONDITIONS Construction permit would not constitute approval of the safety of any design feature or specification Site Characteristics Quality Assurance

• Confirms condition of

• Supports adequate Permit bedrock supporting the implementation of facility commitments in design, Conditions

• Provides for examination of procurement, and excavations by staff, if construction necessary

• Includes change control and notification requirements 7

ADVISORY COMMITTEE ON REACTOR SAFEGUARDS REVIEW Staff presented at subcommittee and full committee meetings ACRS recommended issuance of construction permit

• Combustible gas generation ACRS noted three topics to

• Tritium release levels address with the Hermes operating license application:

• Management of airborne tritium and beryllium in the facility 8

NOVEL ISSUES FROM SAFETY REVIEW Molten Salt High Temperature TRISO Fuel Coolant Materials Functional Passive Accident Containment Response 9

Chris van Wert S e n i o r Te c h n i c a l A d v i s o r, NRR/DSS 10

HERMES TRISO FUEL DESIGN Hermes will use TRISO fuel particles embedded in a carbon matrix pebble

• TRISO particle specification based on U.S.

Department of Energy (DOE) Advanced Gas Reactor (AGR) program

• Forms 4 of 5 fission product barriers credited for functional containment

• TRISO particles arranged in annulus near outer surface of pebble From PSAR Figure 4.2-2 (ML23151A743)

Pebbles are buoyant in Flibe and travel upwards through the core 11

FUEL REVIEW APPROACH NRC staff evaluated the Kairos NRC staff evaluated the Kairos fuel pebble design and the TRISO particle design against the planned fuel qualification testing previously approved generic plan considering expected topical report for TRISO particles conditions 12

OVERCOMING TECHNICAL CHALLENGES: FUEL Precedent?

No overpower transient (e.g., insertion of excess reactivity) testing was performed during the DOE AGR program Is overpower transient Scenario?

testing Limiting rate of reactivity insertion is expected to be control element withdrawal at the maximum needed? withdrawal rate Hermes Design?

Rod ejection is precluded by low differential pressure 13

Alexander Chereskin M a t e r i a l s E n g i n e e r, N R R / D A N U 14

MOLTEN SALT COOLANT Reactor coolant will be a lithium fluoride - beryllium fluoride mixture: Flibe

• Advantageous heat transfer properties Properties

• Thermally and radiolytically stable at high temperatures

• Contains beryllium Challenges

• Transmutation of lithium will generate tritium to be managed Figure from ML23109A130 15

MOLTEN SALT COOLANT REVIEW CONSIDERATIONS Supports functional containment by retaining radionuclides

• Molten salts demonstrated experience retaining salt-soluble radionuclides

• Low vapor pressure Salt composition influences properties of the salt

• Composition to be maintained within specification

• Requires chemistry control to monitor and potentially correct salt composition 16

HIGH TEMPERATURE MATERIALS First CP to reference ASME BPVC* Section III Division 5, "High Temperature Materials"

• Endorsed in NRC Regulatory Guide 1.87, Revision 2 Metallic Materials

• 316H stainless steel for all safety-related components Graphite Materials

• ET-10 graphite for reflector From PSAR Figure 4.3-1 (ML23151A743)

• American Society of Mechanical Engineers Boiler and Pressure Vessel Code 17

MATERIALS QUALIFICATION AND ENVIRONMENTAL EFFECTS Irradiation Temperature Compatibility of 316H stainless steel with Stress/Strain molten Flibe

• Operation Condition

• Noise/Vibration/

Stress/Strain Impact Stress/Strain -

• Qualification program for assessing - Material Environment degradation of 316H stainless steel in Flibe environment Material Environment

• Composition

• Composition

• Microstructure

• Potential

• In-situ Evolution

• Impurity Program to qualify ET-10 graphite for

• Flow rate reflector components Material - Environment

• Applies ASME BPVC Section III Division 5 Figure adapted from ML23102A179 18

Michelle Hart S e n i o r R e a c t o r E n g i n e e r, NRR/DANU 19

FUNCTIONAL CONTAINMENT a barrier, or a set of barriers taken together, that effectively limits the physical transport of radioactive materials to the environment*

PHYSICAL BARRIERS OPERATING CONDITIONS TRISO fuel layers Near-atmospheric primary pressure Flibe coolant Large margin to TRISO fuel design temperature expected FUEL FORM COOLANT DESIGN 1600 °C design temperature Stable at high temperatures Radionuclide retention

• SECY-18-0096, Functional Containment Performance Criteria for Non-Light-Water-Reactors (ML18114A546) 20

FUNCTIONAL CONTAINMENT AND RADIOLOGICAL CONSEQUENCE ANALYSIS Consequences are bounding for all postulated events Expected demonstrable leak rate assumptions are supported

• Fuel testing and surveillance

• Technical Specification on coolant and cover gas fission product concentrations Analysis of overall capability of the Hermes test reactor, including the SSCs that provide radionuclide containment function, is acceptable 21

FUNCTIONAL CONTAINMENT PERFORMANCE CRITERIA PSAR describes the components and operating conditions that define the Hermes test reactor functional containment Key performance criteria

• Specified acceptable system radionuclide release design for specific SSCs ensure limits for the fuel the MHA remains

• Circulating activity limits for the Flibe coolant bounding The acceptability of the functional containment is demonstrated through design and analysis of these individual features and their combined capability 22

Alexandra Siwy, P.E.

S e n i o r N u c l e a r E n g i n e e r, NRR/DANU 23

PASSIVE ACCIDENT RESPONSE Electrical power and operator actions are not required Reactor trip signal removes power from electromagnetic clutch, causing shutdown elements to fall into the core by gravity and shut down the reactor Decay heat removal system provides safety-related heat removal

• No component change of state when needed to mitigate a postulated event

• Designed to provide cooling for up to 7 days to mitigate a postulated event when normal cooling is unavailable 24

DECAY HEAT REMOVAL SYSTEM Staff review considered:

• Heat removal capacity and redundancy

• Phenomena that could affect performance

• Potential for overcooling Kairos test program will confirm performance Figure from ML23109A130 25

HERMES PASSIVE ACCIDENT RESPONSE REVIEW CONSIDERATIONS Reviewed the design and performance of each of the relevant SSCs, as well as their integral response in the Kairos example calculations Performed independent scoping analyses to gain insights on transient behavior and compared against Kairos's calculations Kairos will perform a variety of tests to confirm SSC performance, including:

• Shutdown element insertion

• Fluidic diode for natural circulation

• Decay heat removal system performance 26

ACRONYMS

• ACRS - Advisory Committee on Reactor Safeguards

• AGR - Advanced Gas Reactor

• ASME - American Society of Mechanical Engineers

• BPVC - Boiler and Pressure Vessel Code

• CFR - Code of Federal Regulations

• CP - construction permit

• DANU - Division of Advanced Reactors and Non-Power Production and Utilization Facilities

• DOE - U.S. Department of Energy

• DSS - Division of Safety Systems

• Flibe - molten salt made from a mixture of lithium fluoride and beryllium fluoride 27

ACRONYMS

• MHA - maximum hypothetical accident

• NRC - U.S. Nuclear Regulatory Commission

• NRR - Office of Nuclear Reactor Regulation

• NUREG - U.S. Nuclear Regulatory Commission technical report designation

• OL - operating license

• PSAR - preliminary safety analysis report

• SE - safety evaluation

• SS - stainless steel

• SSCs - structures, systems, and components

• TRISO - tristructural isotropic 28