consume much more of the fuel and leave only short-lived waste. Most MSR designs are derived from the 1960s Molten-Salt Reactor Experiment (MSRE). Variants include the conceptual Dual fluid reactor that uses lead as a cooling medium with molten salt fuel, commonly a metal chloride, e.g. plutonium(III) chloride, to aid in greater closed-fuel cycle capabilities. Other notable approaches include the Stable Salt Reactor (SSR) concept, which encases the molten salt in the well-established fuel rods of conventional reactors. This latter design was found to be the most competitive by consultancy firm Energy Process Development in 2015. Another design under development is TerraPower's Molten Chloride Fast Reactor. This concept mixes the liquid natural uranium and molten chloride coolant in the reactor core, reaching very high temperatures at atmospheric pressure. Another notable feature of the MSR is the possibility of a thermal spectrum nuclear waste-burner. Conventionally only fast spectrum reactors have been considered viable for utilization or reduction of the spent nuclear fuel. Thermal waste-burning was achieved by replacing a fraction of the uranium in the spent nuclear fuel with thorium. The net production rate of transuranic elements (e.g. plutonium and americium) is below the consumption rate, thus reducing the nuclear storage problem, without the nuclear proliferation concerns and other technical issues associated with a fast reactor. Supercritical-water-cooled reactor (SCWR) The supercritical water reactor (SCWR) is a reduced moderation water reactor concept. Because the average speed of the fission-causing neutrons within the fuel is faster than thermal neutrons, it is more accurately termed an epithermal reactor than a thermal reactor. It uses supercritical water as the working fluid. SCWRs are basically light water reactors (LWR) operating at higher pressure and temperatures with a direct, once-through heat exchange cycle. As commonly envisioned, it would operate on a direct cycle, much like a boiling water reactor (BWR). Since it uses supercritical water (not to be confused with critical mass) as the working fluid, it would have only one water phase. This makes the heat exchange method more similar to a pressurized water reactor (PWR). It could operate at much higher temperatures than both current PWRs and BWRs. Supercritical water-cooled reactors (SCWRs) offer high thermal efficiency (i.e., about 45% vs. about 33% efficiency for current LWRs) and considerable simplification. The mission of the SCWR is generation of low-cost electricity. It is built upon two proven technologies, LWRs, the most commonly deployed power generating reactors, and