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	[[File:MSRE_Reactor.JPG\|300px\|thumb\|Figure 1. The MSR used in the Oak Ridge [[Molten salt reactor experiment]] in the 1960's.<Ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/a/ab/MSRE_Reactor.JPG</ref>]]		[[File:MSRE_Reactor.JPG\|300px\|thumb\|Figure 1. The MSR used in the Oak Ridge [[Molten salt reactor experiment]] in the 1960's.<Ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/a/ab/MSRE_Reactor.JPG</ref>]]

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J.williams at 16:57, 12 August 2015

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[[Category:Done 2015-07-01]]
[[File:MSRE_Reactor.JPG|300px|thumb|Figure 1. The MSR used in the Oak Ridge [[Molten salt reactor experiment]] in the 1960's.<Ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/a/ab/MSRE_Reactor.JPG</ref>]]

<onlyinclude>'''Molten salt reactors''' ('''MSRs''') are a [[Generation IV nuclear reactors|Generation IV]] [[nuclear reactor]] that use molten salts (high [[temperature]] liquid salts) as their [[nuclear fuel]] in place of the conventional solid fuels used in the world's current reactors. The use of fluids allows for it to act both as their [[nuclear fuel|fuel]] (producing the heat) and coolant (transferring the heat).</onlyinclude><ref name=win>What is nuclear?. (June 26 2015). ''Molten Salt Reactors'' [Online], Available: http://www.whatisnuclear.com/reactors/msr.html</ref>

These reactors have been designed in many different ways using different fuels. All of these reactors initially have their fuel chemically bonded to fluoride, which is then dissolved into a molten carrier salt. The most commonly proposed carrier salt is a mixture of LiF (Lithium Fluoride) and BeF<sub>2</sub> (Beryllium Fluoride) commonly referred to as FLiBe.<ref name=Book1>D. LeBlanc, “Molten salt reactors: A new beginning for an old idea,” Nucl. Eng. Des., vol. 240, no. 6, pp. 1644–1656, Jun. 2010.</ref> MSRs have not been implemented since the shut down of the [[Molten salt reactor experiment|Molten Salt Reactor Experiment]] (MSRE) in 1969. This is primarily due to technical issues associated with the high temperature and corrosive nature of the salts.

Many countries around the world are actively pursuing research and development of MSRs.<ref name=win/>

==How do they work?==
[[File:FLiBe.png|250px|thumb|Figure 2. Molten FLiBe.<Ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/d/d4/FLiBe.png</ref>]]

The goal with any reactor is to produce [[thermal energy]] through the use of [[nuclear chain reaction]]s. The way this is done varies drastically between reactors, and molten salt reactors are perhaps one of the most unique. Modern reactors currently use solid fuels in their operation, with [[uranium]] being the dominant fuel for these. MSRs however dissolve their fuel in a molten salt mixture, allowing for many interesting benefits which will be discussed in the [[Molten salt reactor#Benefits|section below]]. First it is important to understand the reactor's operation.

In a basic molten salt reactor, [[uranium enrichment|enriched uranium]] (Uranium-235 or -233) is dissolved in a single molten salt solution. The core consisting of a [[neutron moderator]] allows the salt solution to flow at high [[temperature]]s - [[celsius|700°C]] or higher - while remaining at fairly low [[pressure]]s.<Ref name=wna>World Nuclear Association. (July 3, 2015). ''Molten Salt Reactors'' [Online], Available: http://www.world-nuclear.org/info/Current-and-Future-Generation/Molten-Salt-Reactors/</ref> The use of low pressures is an important safety feature, as the risk of an equipment malfunction is greatly diminished. The [[heat]] generated by the nuclear reactions in the salt would be [[heat transfer|transferred]] to a secondary circuit, which would heat up water to [[steam]] and from there produce [[electricity]].

The concept of this basic MSR could be expanded to various other operating features, with perhaps the most promising being its use as a [[breeder reactor]]. This means it would produce more [[fissile]] fuel than it required in the first place!

[[File:msr.png|700px|thumb|center|Figure 3. Diagram of a Molten Salt Reactor.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/0/08/Molten_Salt_Reactor.svg</ref>]]

===Use as a breeder reactor===

The molten salt breeder reactor (MSBR) expands on the basic MSR operating principle. Instead of a single fluid system as described above, a second molten salt fluid is introduced for the breeding of fissile isotopes. The first fluid would contain a [[fissile]] fuel (Uranium-235, or other) which is the "driver" of the nuclear reaction - the fission of it provides neutrons to the second loop, moderated to intermediate to low speeds, along with its normal chain reaction providing useful energy.<ref name=wna/> The second fuel loop would contain a [[fertile]] fuel, which could absorb these neutrons and eventually [[transmutation|transmute]] into a fissile fuel. It would breed more of this new fissile fuel than would be used to do so, hence the name "breeding".

The operation of the MSBR is promising for the use of [[thorium]] as a nuclear fuel, since it has lots of potential in nuclear reactor technology but is currently not in use.<ref name=win/> A type of MSBR that would use thorium is the Liquid Fluoride Thorium Reactor (LFTR). In this reactor, thorium would absorb neutrons from the fissile loop, and would produce uranium-233 by a series of [[beta decay]]s. The uranium-233 can be chemically extracted from this loop, and injected into the fissile loop, thereby extending fuel life of the reactor and reducing [[nuclear waste]].

==Benefits and Drawbacks==

MSRs have many great benefits, however benefits cannot come without some problems. For a more complete story of the pros and cons, visit "[http://www.whatisnuclear.com/reactors/msr.html What is nuclear?]".

====Benefits====

*'''Fission products can be removed or added while the plant is operational.''' Allows for removal of neutron absorbing materials that are produced during fission and for [[on-line refueling]].<ref name=ine>J.R. Lamarsh and A.J. Baratta, "Power Reactors and Nuclear Steam Supply Systems" in ''Introduction to Nuclear Engineering'', 3rd ed., Upper Saddle River, NJ: Prentice Hall, 2001, ch.4, sec.5, pp. 136-185</ref>
*'''Use of thorium''' is promising since it is more abundant than uranium, and in combination with on-line refueling its use can be optimized.<ref name=wna/>
*'''Fuel fabrication''' is limited to [[chemical]] processes, rather than the need to manufacture fuel rods, assemblies, tubes, etc.
*'''High temperatures''' increase [[efficiency]] of heat transfer, and '''low pressures''' ensure safer operation while reducing the size and costs of the [[reactor building]].<ref name=win/>
*'''Improved safety features''' such as a drain tank mechanism where the fuel can be passively cooled in the event of overheating (see Figure 3), lower pressures, and negative temperature coefficient of reactivity meaning if the temperature increases the fuel expands and becomes less [[radioactivity|radioactive]].<Ref name=win/>

====Drawbacks====

*'''Material degradation''' can be a problem due to the corrosive nature of the chemicals present in the fluid.
*'''Production of radioactive Tritium''' is unavoidable if lithium is used, and it is capable of escaping to the environment because it is so small.<ref name=win/>
*'''Complex chemical plant operation and maintenance''' would increase costs and introduce many complications in operation.
*'''Proliferation concerns''' are present due to the difficulty of fissile materials tracking inside of the core, and if thorium is used as the fertile fuel in breeding its byproduct proactinium-233 could be harnessed to make weapons since it decays to weapons-grade uranium-233.<ref name=win/>

=== Completed Designs ===
*[[Aircraft reactor experiment|Aircraft Reactor Experiment]] (ARE) (1947-1961)
*[[Molten salt reactor experiment|Molten Salt Reactor Experiment]] (MSRE) (1965-1969)

=== Proposed Designs ===
*[[Liquid fluoride thorium reactor|Liquid Fluoride Thorium Reactor]] (LFTR)
*Molten Salt Breeder Reactor
*Fuji MSR

== References ==
{{reflist}}
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Molten salt reactor - Revision history

Jmdonev at 13:57, 5 February 2025

J.williams: 1 revision imported

J.williams at 16:57, 12 August 2015