Patent Number: 
Section: claims

1. A nuclear reactor for operative connection to a power conversion system, the reactor comprising:a containment vessel;a reactor core housed within the containment vessel;a neutron reflector spaced from the containment vessel and positioned between the core and the containment vessel;a liquid fuel comprised of a nuclear fission material dissolved in a molten salt enclosed within the core;a plurality of heat transfer pipes, each pipe having a first end and a second end, the first end being positioned within the reactor core for absorbing heat from the fuel;a heat exchanger external to the containment vessel, the heat exchanger receiving the second end of each heat transfer pipe for transferring heat from the core to the heat exchanger; andat least two reactor shut down systems that together act as redundant fail-safe systems comprising a first shut down system and, at least one second shut down system, wherein the first shut down system comprises:a rotatable member mechanism comprising:a plurality of rotatable members positioned within the neutron reflector and having a neutron absorber section and a non-absorber section; and,a rotating drive mechanism operatively connected by activation rods to each rotatable member for rotating the rotatable member to move the neutron absorber section to one of a first position facing the core and a second position facing away from the core, andthe second shut down system comprises one or both of a neutron absorber activation system and a melt-plug mechanism. 2. The nuclear reactor recited in claim 1 wherein the second shut down system is the melt-plug mechanism and comprises:an opening in the containment vessel;a chamber fluidly connected to the opening in the containment vessel;a melt plug to plug the opening in the containment vessel;the melt plug being made of a material that melts at a predetermined temperature deemed to be indicative of unsafe temperature conditions within the reactor core. 3. The nuclear reactor recited in claim 2 wherein the melt plug is made of an alloy and the predetermined temperature is between 650° C.−900° C. 4. The nuclear reactor recited in claim 2 further comprising:a barrier housing for holding the containment vessel; anda plurality of heat dissipation elements extending from the chamber into the barrier housing. 5. The nuclear reactor recited in claim 1 further comprising:a central axis extending through the core;wherein the second shut down system comprises the neutron absorber activation system comprising:a hollow tube defining a cavity and being positioned coaxially to the central axis and extending from an area above the core into the core;a gate separating a first portion of the hollow tube above the core from a second portion of the hollow tube within the core;a neutron absorber material housed in an unactivated position within the first portion of the hollow tube;an activation rod operatively connected to the gate;a release member for releasing the actuation rod from the unactivated position to move to an activated position, wherein in the activated position, the actuation rod opens the gate to release the neutron absorber material into the cavity within the second portion of the hollow tube in proximity to the fuel to absorb neutrons from the fuel sufficient to shut down the reactor. 6. The nuclear reactor recited in claim 5 wherein the neutron absorber shut down system further comprises:a guide positioned within the hollow tube coaxial to the central axis and defining a channel between the hollow tube and the guide for receiving the neutron absorber material upon release thereof in the activated position. 7. The nuclear reactor recited in claim 1 further comprising:a barrier housing for holding the containment vessel. 8. The nuclear reactor recited in claim 1 wherein at least one of the first and at least one second shut down systems is a passive system and at least one is an active system. 9. The nuclear reactor recited in claim 1, wherein the containment vessel has an interior and an exterior, further comprising:a plurality of cooling fins on the exterior of the containment vessel. 10. The nuclear reactor recited in claim 1, wherein the containment vessel has an interior and an exterior, further comprising:a lining on the interior of the containment vessel comprised of a fission gas absorbing material. 11. The nuclear reactor recited in claim 1 wherein the fuel comprises one or both of a uranium halide or a uranium oxyhalide, dissolved in one or more of a potassium, magnesium, or sodium salt. 12. The nuclear reactor recited in claim 1 wherein the contaimnent vessel is in the shape of a cylinder. 13. A nuclear reactor for operative connection to a power conversion system, the reactor comprising:a containment vessel;a reactor core housed within the containment vessel;a neutron reflector spaced froze the containment vessel and positioned between the core and the containment vessel;a livid fuel comprised of a nuclear fission material dissolved in a molten salt enclosed within the core;a plurality of heat transfer pipes, each pipe having a first end and a second end, the first end being positioned within the reactor core for absorbing heat from the fuel;a heat exchanger external to the containment vessel, the heat exchanger receiving the second end of each heat transfer pipe for transferring heat from the core to the heat exchanger; andat least three reactor shut down systems comprising a first shut down system, a second shut down system, and a third shut down system, the first shut down system comprising:a rotatable member mechanism comprising:a plurality of rotatable members positioned evenly within the neutron reflector, each rotatable member having a neutron absorber section and a non-absorber section; and,a rotating drive mechanism operatively connected to each rotatable member for rotating the rotatable member to move the neutron absorber section to one of a first position facing the core and a second position facing away from the core;the second shut down s stem comprising:a melt-plug mechanism comprising:an opening in the containment vessel;a chamber fluidly connected to the opening in the containment vessel;a first melt plug, to plug the opening in the containment vessel;the first melt plug being made of a material that melts at a predetermined melting temperature deemed to be indicative of unsafe temperature conditions within the reactor core; and the third shut down system comprising:a central axis extending through the core and a neutron absorber activation system comprisinga hollow tube defining a cavity and being positioned coaxially to the central axis and extending from an area above the core into the core;a gate separating a first portion of the hollow tube above the core from a second portion of the hollow tube within the core;a neutron absorber material housed in an unactivated position within the first portion of the hollow tube;an activation rod operatively connected to the gate;a release member for releasing the actuation rod from the unactivated position to move to an activated position, wherein in the activated position, the actuation rod opens the gate to release the neutron absorber material into the cavity within the second portion of the hollow tube in proximity to the fuel to absorb neutrons from the fuel sufficient to shut down the reactor. 14. The nuclear reactor recited in claim 13 further comprising:a passage through the neutron reflector from the reactor core to a space defined between the containment vessel and the neutron reflector;a second melt plug to plug the passage;the second melt plug being made of a material that melts at a predetermined melting temperature deemed to be indicative of unsafe temperature conditions within the reactor core. 15. The nuclear reactor recited in claim 14 further comprising:a heating element positioned proximate to at least one of the opening in the containment vessel for heating the first melt plug, to the predetermined melting temperature of the first melt plug and the passage for heating the second melt plug to the predetermined melting temperature of the second melt plug, anda heating element controller electrically connected to the heating element for manual activation of the heating element. 16. The nuclear reactor recited in claim 13 wherein the neutron absorber shutdown system further comprises:a guide positioned within the hollow tube coaxial to the central axis and defining a channel between the hollow tube and the guide for receiving the neutron absorber material upon release thereof in the activated position.