Résumé
A liquid metal cooled nuclear reactor, or LMR is a type of nuclear reactor where the primary coolant is a liquid metal. Liquid metal cooled reactors were first adapted for breeder reactor power generation. They have also been used to power nuclear submarines. Due to their high thermal conductivity, metal coolants remove heat effectively, enabling high power density. This makes them attractive in situations where size and weight are at a premium, like on ships and submarines. Most water-based reactor designs are highly pressurized to raise the boiling point (thereby improving cooling capabilities), which presents safety and maintenance issues that liquid metal designs lack. Additionally, the high temperature of the liquid metal can be used to drive power conversion cycles with high thermodynamic efficiency. This makes them attractive for improving power output, cost effectiveness, and fuel efficiency in nuclear power plants. Liquid metals, being electrically highly conductive, can be moved by electromagnetic pumps. Disadvantages include difficulties associated with inspection and repair of a reactor immersed in opaque molten metal, and depending on the choice of metal, fire hazard risk (for alkali metals), corrosion and/or production of radioactive activation products may be an issue. Liquid metal coolant has been applied to both thermal- and fast-neutron reactors. To date, most fast neutron reactors have been liquid metal cooled fast reactors (LMFRs). When configured as a breeder reactor (e.g. with a breeding blanket), such reactors are called liquid metal fast breeder reactors (LMFBRs). Suitable liquid metal coolants must have a low neutron capture cross section, must not cause excessive corrosion of the structural materials, and must have melting and boiling points that are suitable for the reactor's operating temperature. Liquid metals generally have high boiling points, reducing the probability that the coolant can boil, which could lead to a loss-of-coolant accident.
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