Sodium-cooled fast reactor

Short description: Type of nuclear reactor cooled by molten sodium

This article includes a list of general references, but it remains largely unverified because it lacks sufficient corresponding inline citations. Please help to improve this article by introducing more precise citations. (November 2025) (Learn how and when to remove this template message)

|

Pool type sodium-cooled fast reactor (SFR)

A sodium-cooled fast reactor (SFR) is a fast neutron reactor cooled by liquid sodium.

The initials SFR in particular refer to two Generation IV reactor proposals, one based on existing liquid metal cooled reactor (LMFR) technology using mixed oxide fuel (MOX), and one based on the metal-fueled integral fast reactor.

Currently China, Russia and India have operational sodium-cooled fast reactors (see the list of reactors).[1]

## Contents

* 1 History
* 1.1 TerraPower - Natrium
* 1.2 Canada
* 2 Fuel cycle
* 3 Sodium coolant
* 3.1 Pool or loop type
* 3.2 Advantages
* 3.3 Disadvantages
* 4 Design goals
* 5 The list of reactors
* 6 See also
* 7 References
* 8 External links

## History

### TerraPower - Natrium

In 2020, Natrium received an $80M grant from the US Department of Energy for development of its SFR. The program plans to use High-Assay, Low Enriched Uranium fuel containing 5-20% uranium. The reactor was expected to be sited underground and have gravity-inserted control rods. Because it operates at atmospheric pressure, a large containment shield is not necessary. Because of its large heat storage capacity, it was expected to be able to produce surge power of 500 MWe for 5+ hours, beyond its continuous power of 345 MWe.[2]

In the United States, TerraPower (using its Traveling Wave technology) is building its own reactor along with molten salt energy storage in partnership with GEHitachi's PRISM integral fast reactor design, under the Natrium appellation in Kemmerer, Wyoming.[3][4][5][6]

Non-nuclear construction began in 2024, while the work on the nuclear island is expected to begin in 2026.[7][8] The NRC issued the construction permit for Kemmerer Unit 1 on March 4, 2026.[9]

### Canada

In 2023, ARC Clean Technology Canada signed a memorandum of understanding with the Government of Alberta according to which Invest Alberta entity will support ARC's ARC-100 sodium-cooled 100 MWe reactor (based on Experimental Breeder Reactor II). ARC said that ARC-100 could become operational in 2029. ARC-100 project is a pool type reactor.[10]

## Fuel cycle

The nuclear fuel cycle employs a full actinide recycle with two major options: One is an intermediate-size (150–600 MWe) sodium-cooled reactor with uranium-plutonium-minor-actinide-zirconium metal alloy fuel, supported by a fuel cycle based on pyrometallurgical reprocessing in facilities integrated with the reactor. The second is a medium to large (500–1,500 MWe) sodium-cooled reactor with mixed uranium-plutonium oxide fuel, supported by a fuel cycle based upon advanced aqueous processing at a central location serving multiple reactors. The outlet temperature is approximately 510–550 degrees C for both.

## Sodium coolant

Liquid metallic sodium may be used to carry heat from the core. Sodium has only one stable isotope, sodium-23, which is a weak neutron absorber. When it does absorb a neutron it produces sodium-24, which has a half-life of 15 hours and decays to stable isotope magnesium-24.

### Pool or loop type

Schematic diagram showing the difference between the Pool and Loop designs of a liquid metal fast breeder reactor

The two main design approaches to sodium-cooled reactors are pool type and loop type.

In the pool type, the primary coolant is contained in the main reactor vessel, which therefore includes the reactor core and a heat exchanger. The US EBR-2, French Phénix and others used this approach, and it is used by India's Prototype Fast Breeder Reactor and China's CFR-600.

In the loop type, the heat exchangers are outside the reactor tank. The French Rapsodie, British Prototype Fast Reactor and others used this approach.

### Advantages

All fast reactors have several advantages over the current fleet of water based reactors in that the waste streams are significantly reduced. Crucially, when a reactor runs on fast neutrons, the plutonium isotopes are far more likely to fission upon absorbing a neutron. Thus, fast neutrons have a smaller chance of being captured by the uranium and plutonium, but when they are captured, have a much bigger chance of causing a fission. This means that the inventory of transuranic waste is non existent from fast reactors.

The primary advantage of liquid metal coolants, such as liquid sodium, is that metal atoms are weak neutron moderators. Water is a much stronger neutron moderator because the hydrogen atoms found in water are much lighter than metal atoms, and therefore neutrons lose more energy in collisions with hydrogen atoms. This makes it difficult to use water as a coolant for a fast reactor because the water tends to slow (moderate) the fast neutrons into thermal neutrons (although concepts for reduced moderation water reactors exist).

Another advantage of liquid sodium coolant is that sodium melts at 371K (98°C) and boils / vaporizes at 1156K (883°C), a difference of 785K (785°C) between solid / frozen and gas / vapor states. By comparison, the liquid temperature range of water (between ice and gas) is just 100K at normal, sea-level atmospheric pressure conditions. Despite sodium's low specific heat (as compared to water), this enables the absorption of significant heat in the liquid phase, while maintaining large safety margins. Moreover, the high thermal conductivity of sodium effectively creates a reservoir of heat capacity that provides thermal inertia against overheating.[11] Sodium need not be pressurized since its boiling point is much higher than the reactor's operating temperature, and sodium does not corrode steel reactor parts, and in fact, protects metals from corrosion.[11] The high temperatures reached by the coolant (the Phénix reactor outlet temperature was 833K (560°C)) permit a higher thermodynamic efficiency than in water cooled reactors.[12] The electrically conductive molten sodium can be moved by electromagnetic pumps.[12]

The fact that the sodium is not pressurized implies that a much thinner reactor vessel can be used (e.g. 2 cm thick). Combined with the much higher temperatures achieved in the reactor, this means that the reactor in shutdown mode can be passively cooled. For example, air ducts can be engineered so that all the decay heat after shutdown is removed by natural convection, and no pumping action is required. Reactors of this type are self-controlling. If the temperature of the core increases, the core will expand slightly, which means that more neutrons will escape the core, slowing down the reaction.

### Disadvantages

A disadvantage of sodium is its chemical reactivity, which requires special precautions to prevent and suppress fires. If sodium comes into contact with water it reacts to produce sodium hydroxide and hydrogen, and the hydrogen burns in contact with air. This was the case at the Monju Nuclear Power Plant in a 1995 accident. In addition, neutron capture causes it to become radioactive; albeit with a half-life of only 15 hours.[11]

Another problem is leaks. Sodium at high temperatures ignites in contact with oxygen. Such sodium fires can be extinguished by powder, or by replacing the air with nitrogen. A Russian breeder reactor, the BN-600, reported 27 sodium leaks in a 17-year period, 14 of which led to sodium fires.[13]

## Design goals

Actinides and fission products by half-life v * d * e

Actinides[14] by decay chain | Half-life
range (y)  | Fission products of 235U by yield<ref>Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.</ref>
4n | 4n+1 | 4n+2 | 4n+3
| 4.5–7%  | 0.04–1.25%  | <0.001%
228Ra№ |  |  |  | 4–6  | †  |  | 155Euþ |
244Cmƒ | 241Puƒ | 250Cf  | 227Ac№ | 10–29  | 90Sr  | 85Kr  | 113mCdþ
232Uƒ |  | 238Puƒ | 243Cmƒ | 29–97  | 137Cs  | 151Smþ | 121mSn
248Bk[15] | 249Cfƒ | 242mAmƒ |  | 141–351  |

No fission products
have a half-life
in the range of
100–210 k years ...

| 241Amƒ |  | 251Cfƒ[16] | 430–900
|  | 226Ra№ | 247Bk  | 1.3 k – 1.6 k
240Pu  | 229Th  | 246Cmƒ | 243Amƒ | 4.7 k – 7.4 k
| 245Cmƒ | 250Cm  |  | 8.3 k – 8.5 k
|  |  | 239Puƒ | 24.1 k
|  | 230Th№ | 231Pa№ | 32 k – 76 k
236Npƒ | 233Uƒ | 234U№ |  | 150 k – 250 k  | ‡  | 99Tc₡ | 126Sn
248Cm  |  | 242Pu  |  | 327 k – 375 k  |  | 79Se₡
|  |  |  | 1.53 M  | 93Zr
| 237Npƒ |  |  | 2.1 M – 6.5 M  | 135Cs₡ | 107Pd
236U  |  |  | 247Cmƒ | 15 M – 24 M  |  | 129I₡
244Pu  |  |  |  | 80 M  |

... nor beyond 15.7 M years[17]

232Th№ |  | 238U№ | 235Uƒ№ | 0.7 G – 14.1 G

Legend for superscript symbols
₡ has thermal neutron capture cross section in the range of 8–50 barns
ƒ fissile
m metastable isomer
№ primarily a naturally occurring radioactive material (NORM)
þ neutron poison (thermal neutron capture cross section greater than 3k barns)
† range 4–97 y: Medium-lived fission product
‡ over 200,000 y: Long-lived fission product

The operating temperature must not exceed the fuel's boiling temperature. Fuel-to-cladding chemical interaction (FCCI) has to be accommodated. FCCI is eutectic melting between the fuel and the cladding; uranium, plutonium, and lanthanum (a fission product) inter-diffuse with the iron of the cladding. The alloy that forms has a low eutectic melting temperature. FCCI causes the cladding to reduce in strength and even rupture. The amount of transuranic transmutation is limited by the production of plutonium from uranium. One work-around is to have an inert matrix, using, e.g., magnesium oxide. Magnesium oxide has an order of magnitude lower probability of interacting with neutrons (thermal and fast) than elements such as iron.[18]

High-level wastes and, in particular, management of plutonium and other actinides must be handled. Safety features include a long thermal response time, a large margin to coolant boiling, a primary cooling system that operates near atmospheric pressure, and an intermediate sodium system between the radioactive sodium in the primary system and the water and steam in the power plant. Innovations can reduce capital cost, such as modular designs, removing a primary loop, integrating the pump and intermediate heat exchanger, and better materials.[19]

The SFR's fast spectrum makes it possible to use available fissile and fertile materials (including depleted uranium) considerably more efficiently than thermal spectrum reactors with once-through fuel cycles.

## The list of reactors

Model  | Country  | Thermal power (MW)  | Electric power (MW)  | Year of commission  | Year of decommission  | Notes

|
|
|
|
|
|

BN-350 |  Soviet Union  |  | 350  | 1973  | 1999  | BN-350 used to power a water de-salination plant.
BN-600 |  Soviet Union  |  | 600  | 1980  | Operational  | Expected to operate until 2040[20][21]
BN-800 |  Russia  | 2100  | 880  | 2015  | Operational  |
BN-1200M |  Russia  | 2900  | 1220  |  |  | Preparation stage for construction
CEFR |  China  | 65  | 20  | 2012  | Operational  |
CFR-600 |  China  | 1500  | 600  | 2023  | Under construction  | Two reactors being constructed on Changbiao Island in Xiapu County. The second CFR-600 reactor will open in 2026.[22] |
CFR-1000  |  China  |  | 1200  | After 2030 (est.)  |  | Awaiting approval for construction[23][24]
CRBRP |  United States  | 1000  | 350  | Never built  |  |
EBR-1 |  United States  | 1.4  | 0.2  | 1950  | 1964  |
EBR-2 |  United States  | 62.5  | 20  | 1965  | 1994  |
Fermi 1  |  United States  | 200  | 69  | 1963  | 1975  |
Fast Flux Test Facility |  United States  | 400  |  | 1978  | 1993  | Not for power generation
PFR |  United Kingdom  | 500  | 250  | 1974  | 1994  |
FBTR |  India  | 40  | 13.2  | 1985  | Operational  |
PFBR |  India  |  | 500  | 2025 (est.)  |  | Under commissioning
FBR-600 |  India  |  | 600  | 2025 (est.)  |  | Under commissioning
Monju |  Japan  | 714  | 280  | 1995/2010  | 2010  | Suspended for 15 years. Reactivated in 2010, then permanently closed
Jōyō |  Japan  | 150  |  | 1971  | Under repair  | Expected to be restarted at the end of 2026[25][26]
SNR-300 |  Germany  |  | 327  | 1985  | 1991  | Never critical/operational
Rapsodie |  France  | 40  | 24  | 1967  | 1983  |
Phénix |  France  | 590  | 250  | 1973  | 2010  |
Superphénix |  France  | 3000  | 1242  | 1986  | 1997  | Largest SFR ever built.
ASTRID |  France  |  | 600  | Never built  |  | 2012–2019 €735 million spent

## See also

* Fast breeder reactor
* Fast neutron reactor
* Integral fast reactor
* Lead-cooled fast reactor
* Gas-cooled fast reactor
* Generation IV reactor

## References

1. ↑ "Fast Neutron Reactors | FBR - World Nuclear Association". https://world-nuclear.org/information-library/current-and-future-generation/fast-neutron-reactors.aspx.
2. ↑ "Bill Gates's next-gen nuclear plant packs in grid-scale energy storage" (in en-US). 2021-03-09. https://newatlas.com/energy/natrium-molten-salt-nuclear-reactor-storage/.
3. ↑ Patel, Sonal (2020-09-03). "GE Hitachi, TerraPower Team on Nuclear-Storage Hybrid SMR" (in en-US). https://www.powermag.com/ge-hitachi-terrapower-team-on-nuclear-storage-hybrid-smr/.
4. ↑ "Natrium" (in en-US). https://www.nrc.gov/reactors/new-reactors/advanced/licensing-activities/pre-application-activities/natrium.html.
5. ↑ Patel, Sonal (2022-10-27). "PacifiCorp, TerraPower Evaluating Deployment of Up to Five Additional Natrium Advanced Reactors" (in en-US). https://www.powermag.com/pacificorp-terrapower-evaluating-deployment-of-up-to-five-additional-natrium-advanced-reactors/.
6. ↑ Gardner, Timothy (August 28, 2020). "Bill Gates' nuclear venture plans reactor to complement solar, wind power boom". Reuters. https://www.reuters.com/article/us-usa-nuclearpower-terrapower-idUSKBN25N2U8.
7. ↑ "TerraPower Begins Construction on Advanced Nuclear Project in Wyoming". June 10, 2024. https://www.terrapower.com/terrapower-begins-construction-in-wyoming.
8. ↑ "Suppliers chosen for key components of Natrium demo plant". December 19, 2024. https://www.world-nuclear-news.org/articles/suppliers-chosen-for-key-components-of-natrium-demo-plant.
9. ↑ Timmer, John (March 4, 2026). "TerraPower gets OK to start construction of its first nuclear plant". https://arstechnica.com/science/2026/03/terrapower-gets-ok-to-start-construction-of-its-first-nuclear-plant/.
10. ↑ "The POWER Interview: How a Canadian Small Reactor Will Support Industrial Decarbonization". April 5, 2023. https://www.powermag.com/the-power-interview-how-a-canadian-small-reactor-will-support-industrial-decarbonization/.
11. ↑ 11.0 11.1 11.2 Fanning, Thomas H. (May 3, 2007). "Sodium as a Fast Reactor Coolant". Nuclear Engineering Division, U.S. Nuclear Regulatory Commission, U.S. Department of Energy. http://www.ne.doe.gov/pdfFiles/SodiumCoolant_NRCpresentation.pdf.
12. ↑ 12.0 12.1 Bonin, Bernhard; Klein, Etienne (2012). Le nucléaire expliqué par des physiciens.
13. ↑ Unusual occurrences during LMFR operation, Proceedings of a Technical Committee meeting held in Vienna, 9–13 November 1998, IAEA. Page 53, 122-123.
14. ↑ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
15. ↑ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics 71 (2): 299. doi:10.1016/0029-5582(65)90719-4. Bibcode: 1965NucPh..71..299M.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 y. No growth of Cf248 was detected, and a lower limit for the β− half-life can be set at about 104 y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y."
16. ↑ This is the heaviest nuclide with a half-life of at least four years before the "Sea of Instability".
17. ↑ Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is nearly eight quadrillion years.
18. ↑ "Neutronic Assessment of Transmutation Target Compositions in Heterogeneous Sodium Fast Reactor Geometries". Idaho National Laboratory, U.S. Department of Energy. February 2008. http://www.inl.gov/technicalpublications/Documents/3901052.pdf.
19. ↑ "The Sodium-Cooled Fast Reactor (SFR)". Argonne National Laboratory, US Department of Energy. October 2002. http://www.ipd.anl.gov/anlpubs/2002/10/44547.pdf.
20. ↑ "BN-600 reactor at Beloyarsk aims for further life extension". 7 March 2024. https://www.world-nuclear-news.org/Articles/BN-600-reactor-at-Beloyarsk-aims-to-get-new-life-e.
21. ↑ "Beloyarsk BN-600 fast neutron reactor gets 15-year extension". 2 April 2025. https://www.world-nuclear-news.org/articles/beloyarsk-bn-600-fast-neutron-reactor-gets-15-year-extension.
22. ↑ "China Fast Reactor 600 to be Launched in 2023, 2026 Draws International Attention". May 26, 2021. https://www.techtimes.com/articles/260677/20210526/china-fast-reactor-600-launched-2023-2026-draw-international-attention.htm.
23. ↑ "China finalises design of CFR-1000 fast reactor". July 29, 2025. https://www.neimagazine.com/news/china-finalises-design-of-cfr-1000-fast-reactor.
24. ↑ "China’s next-generation nuclear plans take step forward with fast gigawatt reactor design". July 26, 2025. https://www.scmp.com/news/china/science/article/3319627/chinas-next-generation-nuclear-plans-take-step-forward-fast-gigawatt-reactor-design.
25. ↑ "Japan’s Joyo fast reactor prepares for restart". 10 September 2024. https://www.neimagazine.com/news/joyo-fast-reactor-prepares-for-restart/.
26. ↑ "Japan’s Experimental Fast Reactor “Joyo” to Be Utilized for Radioisotopes Production". 22 August 2025. https://www.jaif.or.jp/en/news/7615.

## External links

* Idaho National Laboratory Sodium-cooled Fast Reactor Fact Sheet
* Generation IV International Forum SFR website
* INL SFR workshop summary
* ALMR/PRISM
* ASME
* Richardson JH (November 17, 2009). "Meet the Man Who Could End Global Warming". Esquire. http://www.esquire.com/features/best-and-brightest-2009/nuclear-waste-disposal-1209-2. "... Eric Loewen is the evangelist of the sodium fast reactor, which burns nuclear waste, emits no CO
2, ..."

* v
* t
* e

Types of nuclear fission reactor

Moderator

Light water|

* Aqueous homogeneous
* Boiling
* BWR
* ABWR
* ESBWR
* Kerena
* Pressurized
* AP1000
* APR-1400
* APR+
* APWR
* ATMEA1
* CAP1400
* CPR-1000
* EPR
* HPR-1000
* ACPR1000
* ACP1000
* VVER
* many others
* Supercritical (SCWR)
* Natural fission

Heavy water|

| D2O|

* Pressurized
* CANDU
* CANDU 6
* CANDU 9
* EC6
* AFCR
* ACR-1000
* AHWR
* CVTR
* IPHWR-X
* PHWR KWU
* MZFR
* R3
* R4 Marviken

|

H2O|

* HWLWR
* ATR
* HW BLWR 250
* Steam-generating (SGHWR)

Organic|

* WR-1

CO2|

* HWGCR
* EL-4
* KKN
* KS 150
* Lucens

Graphite
by coolant

| Water|

| H2O|

* AM-1
* AMB-X
* EGP-6
* RBMK

|

Gas|

| CO2|

* Uranium Naturel Graphite Gaz (UNGG)
* Magnox
* Advanced gas-cooled (AGR)

|

He|

* GTMHR
* MHR-T
* UHTREX
* VHTR (HTGR)
* PBR (PBMR)
* AVR
* HTR-10
* HTR-PM
* THTR-300
* PMR

Molten-salt|

| Fluorides|

* Fuji MSR
* Liquid-fluoride thorium reactor (LFTR)
* Molten-Salt Reactor Experiment (MSRE)
* Integral Molten Salt Reactor (IMSR)
* ThorCon

|

None
(fast-neutron)

* Breeder (FBR)
* Integral (IFR)
* Liquid-metal-cooled (LMFR)
* Small sealed transportable autonomous (SSTAR)
* Traveling-wave (TWR)
* Energy Multiplier Module (EM2)
* Reduced-moderation (RMWR)
* Fast Breeder Test Reactor (FBTR)
* Dual fluid reactor (DFR)

Generation IV|

* Sodium (SFR)
* BN-350
* BN-600
* BN-800
* BN-1200
* CFR-600
* Phénix
* Superphénix
* PFBR
* CEFR
* PFR
* PRISM
* Lead
* Helium gas (GFR)

Others|

* Organic nuclear reactor
* Arbus
* Piqua
* Aircraft Reactor Experiment

* Nuclear fusion reactors
* List of nuclear reactors
* Nuclear technology
* Nuclear accidents

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Sodium-cooled fast reactor. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Engineering:Sodium-cooled_fast_reactor&oldid=4276132"
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template