Workshop on Innovative Nuclear Energy Systems
Tokyo Institute of Technology, Tokyo, 26 January 2024

Development of Next-Generation
Sodium-Cooled Fast Reactor
YAMANO Hidemasa

Sector of Fast Reactor and Advanced Reactor R&D,
Japan Atomic Energy Agency (JAEA)

Outline
1. Nuclear Energy Development in Japan
2. Strategic Roadmap of Fast Reactor Development
3. Development of SFRs in Japan
4. Pool-type SFR for demonstration reactor
5. SFR-related activities in JAEA

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Nuclear Energy Development in Japan
August 24, 2022, GX (Green Transformation) Implementation Council
 Prime minister Kishida expressed that making up for the delay in energy policies is a pressing
issue in implementing GX.
 Items requiring political decisions to expand the introduction of renewable energy were presented
today, including• drastically accelerating the development of power systems,• speeding up the installation of fixed storage batteries, and• promoting offshore wind power and other electricity sources.

 At the same time, items requiring future political decisions concerning nuclear power were also

put forward, such as••

combined efforts by the concerned parties to resume operations,maximum utilization of existing nuclear power plants including the extension of their operation periodwith ensuring their safety being a major precondition, and• development and construction of next-generation innovative reactors that incorporate new safetymechanisms.
 We have discovered additional, distinct advantages of next-generation advanced reactors such as
coexistence with renewables and hydrogen usage. Given these and the global circumstances, we will
identify challenges that Japan’s reactor development will face, and build a technical roadmap that solves allof them.

3Basic policy for Nuclear in Green Transformation (GX)Dec. 22, 2022, Japanese government’s GX Implementation Council
 Basic policy with a ten-year roadmap issued in Dec.
 The maximum use of nuclear power, given that it treats it as “a power source contributing to energy
security and highly effective for decarbonization.” Actualization will be embarked upon starting with the replacement of reactors for which
decommissioning has been decided.” The development and construction of reactors other than those to be replaced will be considered Additional extensions may be allowed where reactor operation was suspended for certain specifiedreasons,” building on the current approach of a reactor operating lifetimes of 40 years, possibly tobe extended to up to 60 years.

Feb. 10, 2023, Japanese government’s GX Implementation Council
 Basic policy toward GX realization
 To achieve decarbonization, stable energy supplies and economic growth simultaneously.
 Public-private GX investments exceeding JPY150 trillion (approximately USD1.14 trillion) during thecoming decade4

Technical roadmap for innovative reactors in Japan Apr.-Nov. 2022, the direction of innovative reactors was discussed in METI Nov. 2022, Japan developed the technical roadmap that shows timeline and milestones ofdetailed processes, and update it as necessary.

 Advanced light water reactors (LWRs)
 Light water-cooled small modular reactors (LW SMRs)
 Fast reactors
 High temperature gas-cooled reactors (HTGRs)
 Fusion reactors

HTGR

LW SMR

Large-scaleadvanced LWR

Fast reactor

Preliminary Roadmap as of 29th Nuclear Energy Subcommittee (Aug. 9, 2022)

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Technical roadmap (Fast reactor)
2020
Construction andoperation ofdemonstration
reactor

R&D

2030

2050
Note tentative timeline

Schemedevelopment

Conceptual
design2040
Safety review

Detailed
designBasic design

Construction
Operationand testing

Demonstration of systems andcomponents using a large-scale test
facility (e.g. Na loop, AthNa)
Irradiation data of fuel andmaterials or licensing(e.g. US ATW, Joyo)

Development of code and standard

Construction andoperation of fuelfabrication plant

Fuel supply

Application

Conceptual
Basic Detailed
designdesign design

Construction
and testing

Operation

Preliminary Roadmap as of 4th Innovative reactor WG under Nuclear Energy Subcommittee (July 29, 2022)

6Strategic Roadmap of Fast Reactor Development (2022)
Demonstration fast reactor

 A revised strategic roadmap was approved bya ministerial meeting on December 23th, 2022.

July 12, 2023, METI
 Selected Mitsubishi Heavy Industries, Ltd.

 2023 Summer: selection of a demonstration

 as the core company in charge of the conceptual
design of the demonstration fast reactor

reactor concept and a core company.

 2024-2028: conceptual design and related

R&D• Severe accident experiments• Irradiation in Joyo
• Material experiments• AtheNa experiment (component
demonstration)
 2026: fuel selection (oxide or metal)
 2028-: Basic design study and licensing
application
 2040s: start operation

 The pool-type sodium-cooled fast reactor
plant concept proposed by Mitsubishi FBRSystems, Ltd. was selected as the target
concept of the demonstration reactor.
 The electric output of the demonstration
reactor is 650MWe.

https://www.meti.go.jp/shingikai/enecho/denryoku_gas/genshiryoku/pdf/036_01_00.pdf
https://www.meti.go.jp/shingikai/energy_environment/kosokuro_kaihatsu/kosokuro_kaihatsu_wg/pdf/021_01_00.pdf
https://www.mhi.com/news/23071202.html

Tank-type sodium-cooled fast reactor(https://www.mhi.com/news/23071202.html)

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Development of sodium cooled fast reactors (SFRs)
in Japan
Development led by JAEA
JSFRDesign Study forCommercialization

Power ： 600~1500 MWe
Temperature ： 500~550ºC

Joyo

Experimental(under safety review byregulator)• Basic and fundamental study• R&D of advanced technologies

Initial Criticality in 1977
Power ：50MWt  100MWt  140MWt
 100MWt (Mk-IV Core)
Temperature ： 435ºC  500ºC  500ºC

led by Private sector
Commercialization• Demonstration of economics• Demonstration of reliability

Scheduled operation by ~2050
Power ： 650 MWe (demonstration)
Temperature ： 500~550ºC

Innovative Technologies for Safety Enhancement
Monju
Prototype(decideddecommissioningin 2016)• Demonstration of reliable operation• Demonstration of innovative technologies

Initial Criticality in 1994
Power ：714MWt / 280MWe, Temperature ： 529ºC8

Main design specifications of the pool-type SFR for
demonstration reactor

ItemPower

Core inlet /outlet coolant
temperature
Fuel type /AssemblyPrimarypumps

Values or Systems

1500MWt / 650 MWe
550/400 deg. C
MOX fuel / Assembly with innerduct which discharges molten fuelThree mechanical pumps

Higurashi, K., et al., Joint IAEA-GIF Workshop on the Safety of Non-Water CooledReactors, Vienna, Austria, 30 May-2 June 2023

ItemValues or Systems
Intermediate
Four IHXs (Straight tubes
Heat Exchangers containing secondary coolant(IHXs)
inside)Secondarypumps

Four mechanical pumps

Powerconversion
systems

Four steam generators, one watersteam turbine

9Main safety features of the pool-type SFR fordemonstration reactor
(i) Reactor shutdownmeasures(ii) Measures toachieve IVR ofdamaged core(iii) Measures fordecay heat removalSafety features
Two active reactor shutdown systems
Passive reactor shutdown measure: Self-Actuated Shutdown System (SASS) usinga Curie point electromagnet
Measures to mitigate the consequence of core damage resulting from anticipatedtransients without scram (ATWS) (reduction of void reactivity to approximately 6$ or
less, provision of the fuel assembly with inner duct structure, transfer of re-molten
fuels from the control rod guide tube, and stable cooling and retention using a corecatcher)Prevent complete loss of decay heat removal function: Decay Heat Removal
System (DHRS) configuration considering the use of natural circulation capability: One immersed Direct Reactor Auxiliary Cooling System (DRACS) Four Intermediate Reactor Auxiliary Cooling Systems (IRACS)
 One penetrated DRACS
Prevent core uncovering and ensure primary coolant paths for decay heat removal:
practical elimination of double leakage by securing high reliability of the main vessel
and the safety vessel

Higurashi, K., et al., Joint IAEA-GIF Workshop on the Safety of Non-Water Cooled
Reactors, Vienna, Austria, 30 May-2 June 2023

10Type of decay heat removal system
PRACS

DRACS

IRACS

Direct Reactor Auxiliary Cooling System Primary Reactor Auxiliary Cooling System

UHSIntermediate Reactor Auxiliary Cooling System

SGUHS
DHX

IHX

IHX
UHS

RACS

RVACS

SGACS

Reactor Auxiliary Cooling System

Reactor Vessel Auxiliary Cooling System

Steam Generator Auxiliary Cooling System

SG

IHX

IHX

UHS
UHS

Reｆ.: S. Kubo et al., A conceptual design study of pool-type sodium-cooled fast reactor with enhanced anti-seismic capability,

11Safety design of Decay heat removal system (DHRS)
Safety design
 Passive reactor
shutdown
 Measures against CDAs
 Measures to secure
decay heat removal
 Containment vessel Measures against
sodium leak and sodiumfire
 Measures against
sodium-water reaction

Higurashi, K., et al., Joint IAEA-GIF Workshop on the Safety of Non-Water Cooled
Reactors, Vienna, Austria, 30 May-2 June 2023

 SDC/SDG Situations of complete loss of heat removal function that
could lead to core damage and failure of the reactor coolant
boundary should be practically eliminated.
 Natural circulation capability should be incorporated into thewhole decay heat removal system as an SFR’s merit.
 Policy Diverse and redundant design
 Incorporate natural circulation capability
 For AOOs and DBAs
• Secure enough heat removal capacity in the case of
single failure• Adopt different types of cooling systems to reduce apossibility of common cause failure DHRS in addition to measures for AOOs and DBAs
• Have an alternative cooling measure against the loss ofcooling systems for AOOs and DBAs
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Safety design of DHRS for AOOs and DBAsIRACSProvided for AOOs andDBAs
Has a capability of NC
Connected to the secondary
heat transport system, andcore cooling by IRACS
relies on the main flow ofthe primary heat transportsystem.

Alternative coolingmeasureNC: Natural circulation cooling
FC: Forced circulation cooling
IRACS: Intermediate Reactor Auxiliary Cooling System
DRACS: Direct Reactor Auxiliary Cooling System

Configuration of DHRS

Reｆ.: S. Kubo et al., A conceptual design study of pool-type sodium-cooled fast reactor with enhanced anti-seismic capability,
Bulletin of the JSME Mechanical Engineering Journal Vol.7, No.3, (2020)
Higurashi, K., et al., Joint IAEA-GIF Workshop on the Safety of Non-Water CooledReactors, Vienna, Austria, 30 May-2 June 2023

13

Safety design of DHRS for AOOs and DBAs
DRACS (immersed type)Provided for AOOs andDBAs
Provided with IRACS from aviewpoint of single failureand diversity
Has a capability of NC
Has DHX in the hot pool forNC through IHXs etc.

Alternative coolingmeasureNC: Natural circulation cooling
FC: Forced circulation cooling
IRACS: Intermediate Reactor Auxiliary Cooling SystemIHX: Intermediate Heat Exchanger
DRACS: Direct Reactor Auxiliary Cooling System
DHX: Heat Exchanger of DRACS

Configuration of DHRS

Reｆ.: S. Kubo et al., A conceptual design study of pool-type sodium-cooled fast reactor with enhanced anti-seismic capability,
Bulletin of the JSME Mechanical Engineering Journal Vol.7, No.3, (2020)
Higurashi, K., et al., Joint IAEA-GIF Workshop on the Safety of Non-Water Cooled
Reactors, Vienna, Austria, 30 May-2 June 2023

14Safety design of DHRS for DECsDRACS (penetrated type)Provided as an alternative coolingmeasure in accordance withSDC/SDG.
Has a capability of NC in primarycooling system
Has a capability of FC insecondary cooling system and theair-cooling system from aviewpoint of diversity.
Independent from DHRSs to copewith AOOs and DBAs.
Has a shutter to prevent bypass
flow from hot pool to cold pool
during normal operation.
The shutter opens in the case ofoperating.

Alternative coolingmeasureReｆ.: S. Kubo et al., A
conceptual design studyof pool-type sodiumcooled fast reactor withenhanced anti-seismic
capability, Bulletin of theJSME MechanicalEngineering Journal
Vol.7, No.3, (2020)

Configuration of DHRS

NC: Natural circulation cooling, FC: Forced circulation cooling, IRACS: Intermediate Reactor Auxiliary
Cooling System, DRACS: Direct Reactor Auxiliary Cooling System, DHRS: Decay Heat Removal System
Higurashi, K., et al., Joint IAEA-GIF Workshop on the Safety of Non-Water Cooled
Reactors, Vienna, Austria, 30 May-2 June 2023

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Development of Fast Reactor Cycle Technology at JAEA
Features of the fast
reactor cycle

Major research anddevelopment○Dozens of times more effective use of uranium resources than the light-water reactor○Reduction of the amount of radioactive waste and significant shortening of the period of
attenuation of radioactivity○Research and development of technologies necessary for practical application of the fastreactor○Technology development aiming at establishment of a fuel cycle○Initiatives to resume operation of the experimental fast reactor “JOYO”[Purpose]• Confirmation of core characteristics andplant performance• Irradiation test of fuels and materials• Basic infrastructure research (RI production,etc.) utilizing the large amount of fastneutrons

Developing simulation technology used in the designof fast reactors, Making rule for safety assurance,conducting safety tests, and construction of new
research facilities are underway.
Examples of researchand development
Heatexchanger Thermal output 100MW (air-cooled) Coolant Liquid sodium
Post-irradiation test
facility

Irradiation device
Assembly inspection
facility

Test equipment(Simulated core structure)

Experimental fast reactor “JOYO”•

Fuel fabrication
Reduction of waste
volume and reductionof radioactive toxicity
through fuel recycling

Reactorcore

Spent fuelStorage facility

Nuclear reactor building

Technology development using researchfacilities in Oarai and Tokai is proceeding toreduce the amount of radioactive waste

Operation of test
equipment

Confirm that the heat exchanger can stably cool thereactor core even in the loss of power
Research and development for practicalapplication of the fast reactor

Fast reactor

Reprocessing

Technology development aiming at establishmentof a fuel cycle

16Experimental fast reactor “Joyo”
Current status
 Joyo has been under NRA review with the new
regulatory requirements since 2017.
 NRA approval for restart in July 2023.

Joyo

 Scheduled to restart in 2026 after seismicreinforcement.
Role of Joyo Demonstrated basic sodium-cooled FRtechnologies.
 Irradiation testing of fuels and materials, andvalidation of innovative technologies for thedevelopment of future reactors.
 Basic research using high fast neutron flux.

Thermal power 100MWFuel
MOX fuel
Coolant
SodiumFirst Criticality 1977
Located in Oarai, Ibaraki Pref.

 Various Irradiation uses. (e.g., Production of
medical RI such as Ac-225)
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Potential role of “Joyo”
as a versatile research platform
For the energy security and innovation
to realize a “carbon net zero” society

For a world free from the threat ofnuclear proliferation and terrorism■Utilization of separated Pu■Development of Pu burnerreactorUse ofseparated Pu■SMR, next generation reactor
development NEXIP■support for private sector’s innovation■ Advanced
fuels&materials
development, safety improvement■collaboration with US and FranceVTR

Production of medical andindustrial isotopes■Production of isotopes for
medical purpose■Isotopes for industrial
application
αrayInternal cancer
therapy■ Minor actinide transmutation■ Transmutation of LLFPReduction ofRadiological hazard of waste

Sustainable use of nuclear energy

Experimental fast reactor“Joyo”■Basic research, multipurpose use■International collaboration■Fusion reactor development（R&D of first wall materials）■Collaboration with universities■ Acceptanceofforeignengineers

Training

Internship forforeign researchers

Human resources
development

Pursuit of nuclear potential

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Concluding remarks
 Many countries have been developing next-generation innovativereactors, such as advanced LWRs including SMRs, fast reactors, hightemperature gas-cooled reactors.
 R&D on innovative reactors is one of the most attractive areas innuclear energy deployment.
 Sodium-cooled fast reactors (SFRs) are recognized to be the mostmature technology in the Generation-IV systems.
 Japan starts the conceptual design of the next SFR for technology
demonstration from 2024 for its operation start in 2040s.
 Student involvement and engagement are necessary for realization of
the next-generation innovative reactors.
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