Sodium-cooled fast reactor

Generator

Electricalpower

Turbine

Core

Cold plenum

Hot plenum

Heatexchanger

Primarysodium(cold)

Secondarysodium

Pump

Pump

Condenser

Controlrods

Heat sink

Steamgenerator

Pump

Primarysodium(hot)

Pool type sodium-cooled fast reactor (SFR)

The sodium-cooled fast reactor (SFR) is a GenerationIV reactor project to design an advanced fast neutron re-actor.It builds on two closely related existing projects, theLMFBR and the Integral Fast Reactor, with the objectiveof producing a fast-spectrum, sodium-cooled reactor.The reactors are intended for use in nuclear power plantsto produce nuclear power from nuclear fuel.

1 Fuel cycle

The nuclear fuel cycle employs a full actinide recycle withtwo major options: One is an intermediate-size (150–600MWe) sodium-cooled reactor with uranium-plutonium-minor-actinide-zirconium metal alloy fuel, supported bya fuel cycle based on pyrometallurgical reprocessing infacilities integrated with the reactor. The second is amedium to large (500–1,500 MWe) sodium-cooled reac-tor with mixed uranium-plutonium oxide fuel, supportedby a fuel cycle based upon advanced aqueous process-ing at a central location serving a number of reactors.The outlet temperature is approximately 510–550 de-grees Celsius for both.

2 Sodium as a coolant

Liquid metallic sodium may be used as the sole coolant,carrying heat from the core. Sodium has only one sta-ble isotope, sodium-23. Sodium-23 is a very weak ab-sorber of neutrons, the absorption of a neutron producing

sodium-24, which has a half-life of 15 hours, decaying tomagnesium-24.

2.1 Advantages

Controlrods

FissileCore

BreederBlanket

BiologicalShielding

Liquidmetalcoolant

Heatexchanger

Steamgenerator

Heatexchanger

Steamgenerator

FissileCore

BreederBlanket

BiologicalShielding

Liquidmetalcoolant

ReactorPool Pump

CoolantLevel

FlowBaffle

ControlRods Steam

Water

Power-generation

loop

Intermediateloop

Intermediateloop

Reactorpool

(primary coolant)

Reactorloop

(primary coolant)

Liquid Metal cooled Fast Breeder Reactors (LMFBR)

"Pool" Design "Loop" Design

(to power turbine)

(from power turbine)

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

An advantage of liquid metal coolants is high heat capac-ity which provides thermal inertia against overheating.[1]Water is difficult to use as a coolant for a fast reactor be-cause water acts as a neutron moderator that slows thefast neutrons into thermal neutrons. While it may be pos-sible to use supercritical water as a coolant in a fast reac-tor, this would require a very high pressure. In contrast,sodium atoms are much heavier than both the oxygen andhydrogen atoms found in water, and therefore the neu-trons lose less energy in collisions with sodium atoms.Sodium also need not be pressurized since its boilingpoint is much higher than the reactor’s operating temper-ature, and sodium does not corrode steel reactor parts.[1]The high temperatures reached by the coolant (up to 550°C) permit a higher thermodynamic efficiency than inwater cooled reactors.[2] The molten sodium, being elec-trically conductive, can be pumped by electromagneticpumps.[2]

2.2 Disadvantages

A disadvantage of sodium is its chemical reactivity,which requires special precautions to prevent and sup-press fires. If sodium comes into contact with water itexplodes, and it burns when in contact with air. This wasthe case at the Monju Nuclear Power Plant in a 1995 ac-cident. In addition, neutrons cause it to become radioac-tive; however, activated sodium has a half-life of only 15hours.[1]

1

2 7 EXTERNAL LINKS

3 Design goals

The operating temperature should not exceed the melt-ing temperature of the fuel. Fuel-to-cladding chemicalinteraction (FCCI) has to be designed against. FCCI iseutectic melting between the fuel and the cladding; ura-nium, plutonium, and lanthanum (a fission product) inter-diffuse with the iron of the cladding. The alloy that formshas a low eutectic melting temperature. FCCI causes thecladding to reduce in strength and could eventually rup-ture. The amount of transuranic transmutation is limitedby the production of plutonium from uranium. A designwork-around has been proposed to have an inert matrix.Magnesium oxide has been proposed as the inert ma-trix. Magnesium oxide has an entire order of magnitudesmaller probability of interacting with neutrons (thermaland fast) than elements like iron.[3]

The SFR is designed for management of high-level wastesand, in particular, management of plutonium and otheractinides. Important safety features of the system includea long thermal response time, a large margin to coolantboiling, a primary system that operates near atmosphericpressure, and intermediate sodium system between theradioactive sodium in the primary system and the waterand steam in the power plant. With innovations to reducecapital cost, such as making a modular design, removing aprimary loop, integrating the pump and intermediate heatexchanger, or simply find better materials for construc-tion, the SFR can be a viable technology for electricitygeneration.[9]

The SFR’s fast spectrum also makes it possible to useavailable fissile and fertile materials (including depleteduranium) considerably more efficiently than thermalspectrum reactors with once-through fuel cycles.

4 Reactors

Sodium-cooled reactors have included:Most of these were experimental plants, which are nolonger operationalRelated:

• Fast Flux Test Facility, United States, a sodium-cooled fast neutron reactor

5 See also

• Fast breeder reactor

• Fast neutron reactor

• Integral Fast Reactor

• Lead-cooled fast reactor

• Gas-cooled fast reactor

• Generation IV reactor

6 References[1] Fanning, Thomas H. (May 3, 2007). “Sodium as a

Fast Reactor Coolant” (PDF). Topical Seminar Series onSodium Fast Reactors. Nuclear Engineering Division,U.S. Nuclear Regulatory Commission, U.S. Departmentof Energy.

[2] Bonin, Bernhard; Klein, Etienne (2012). Le nucléaire ex-pliqué par des physiciens.

[3] Bays SE, Ferrer RM, Pope MA, Forget B (February2008). “Neutronic Assessment of Transmutation TargetCompositions in Heterogeneous Sodium Fast Reactor Ge-ometries” (PDF). Idaho National Laboratory, U.S. De-partment of Energy. INL/EXT-07-13643 Rev. 1.

[4] Plus radium (element 88). While actually a sub-actinide, itimmediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where noisotopes have half-lives of at least four years (the longest-lived isotope in the gap is radon-222 with a half life of lessthan four days). Radium’s longest lived isotope, at 1600years, thus merits the element’s inclusion here.

[5] Specifically from thermal neutron fission of U-235, e.g. ina typical nuclear reactor.

[6] Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965).“The alpha half-life of berkelium-247; a new long-livedisomer of berkelium-248”. Nuclear Physics 71 (2): 299.doi:10.1016/0029-5582(65)90719-4.“The isotopic analyses disclosed a species of mass 248 inconstant abundance in three samples analysed over a pe-riod of about 10 months. This was ascribed to an isomerof Bk248 with a half-life greater than 9 y. No growth ofCf248 was detected, and a lower limit for the β− half-lifecan be set at about 104 y. No alpha activity attributableto the new isomer has been detected; the alpha half-life isprobably greater than 300 y.”

[7] This is the heaviest isotope with a half-life of at least fouryears before the "Sea of Instability".

[8] Excluding those "classically stable" isotopes with half-lives significantly in excess of 232Th, e.g. while 113mCdhas a half-life of only fourteen years, that of 113Cd isnearly eight quadrillion.

[9] Lineberry MJ, Allen TR (October 2002). “The Sodium-Cooled Fast Reactor (SFR)" (PDF). Argonne NationalLaboratory, US Department of Energy. ANL/NT/CP-108933.

7 External links• Idaho National Laboratory Sodium-cooled Fast Re-actor Fact Sheet

3

• Generation IV International Forum SFR website

• INL SFR workshop summary

• ALMR/PRISM

• Richardson JH (November 17, 2009). “Meet theMan Who Could End Global Warming”. Esquire.... Eric Loewen is the evangelist of the sodium fastreactor, which burns nuclear waste, emits no CO2,...

4 8 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

8 Text and image sources, contributors, and licenses

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