Molten-salt reactor advantages

Molten salt reactors (MSRs) are a family of liquid-fueled fission reactor concepts using a fluid molten salt mixture as fuel. Such liquid-fueled reactors benefit from some potential advantages over solid-fueled systems, among which are... 

Mathieu, L., Heuer, D., Merle-Lucotte, E., et al., 2009. Possible configiuations for the thorium molten salt reactor and advantages of the fast non-moderated version. Nuclear Science and Engineering 161, 78—89. 

It may be feasible to burn plutonium in molten fluoride-salt reactors. The solubility of PuFa in mixtures of LiF and BeFa is considerably less than that of UF4, but is reported to be over 0.2 mole % [8], which may be sufficient for criticality even in the presence of fission fragments and non-fissionable isotopes of plutonium but probably limits severely the amount of ThF4 that can be added to the fuel salt. This limitation, coupled with the condition that Pu is an inferior fuel in intermediate reactors, will result in a poor neutron economy in comparison with that of U -fueled reactors. However, the advantages of handling plutonium in a fluid fuel system may make the plutonium-fueled molten-salt reactor more desirable than other possible plutonium-burning systems. 

If the AHTR is used to produce hydrogen, a key issue is the coupling of the two plants via the intermediate heat transport loop. The intermediate heat transfer system has two sets of safety-related functional requirements (1) protect the reactor and chemical plant from transients and accidents in either facility and (2) protect the reactor and chemical plant from transients and accidents within the intermediate heat transfer system. Molten salts may offer major safety advantages compared to helium for this application. 

The AHTR has a higher potential efficiency than the GT-MHR at the same reactor eoolant exit temperatures, because delivery of most of the heat at near-constant high temperatures allows the use of more-efficient Camot-like power cycles. The benefit of these advanced cycles is increased efficiency, resulting in up to 20% increased electrical output for the same thermal power. The cost of this improvement is some increased system complexity. Molten salt coolants present the most promising approach to take advantage of this potential benefit. 

Inspection. Molten salts are transparent. This is a major advantage over liquid-metal reactors where inspection has been a major issue. 

A few advanced solid fuel concepts were considered in this study to indicate some of the improvements that might obtained in reactor design or operation. There are no operating data for these fuel forms,. so only the perceived advantages of each fuel form considered are briefly presented. The feasibility of the fabrication of these advanced fuel forms was assumed mostly on the basis of the known feasibility of the fabrication of similar systems. Liquid fuel forms, such as molten salts, were also considered, but the containment of these highly corrosive materials was considered to be a major unsolved problem that would significantly delay their u.se in plutonium burning. 

A considerable nuclear advantage would exist in a reactor with an uncanned graphite moderator exposed to the molten salts. Long-time exposure of graphite to a molten salt results in the salt penetrating the available pores, but it is probable, with the "impermeable types of... 

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