Abstract: A nuclear reactor having a liquid metal or molten salt coolant in a riser space 130?, has a cylindrical containment vessel 134 with a reactor vessel 120?, at least two lobes 121, preferably three to nine lobes 121, each lobe 121 interconnected with the other lobe(s) and each containing a fast reactor core, 116?, 116?, 116? and 116??.

Abstract: A tertiary shutdown system for a liquid metal reactor that eliminates the need for considering an ATWS in setting the thermal power limits of the reactor. The shutdown system includes a reservoir of neutron absorber material that is sealed by a valve that may actively dispense the absorber upon operator command, into a stagnant pool of sodium in the core that is confined to prevent the absorber material from entering the coolant flowing through the core. Additionally, the valve may be passively open to release the absorber material into the stagnant pool of sodium when the temperature at the valve exceeds a predetermined limit.

Abstract: A nuclear reactor having a liquid metal or molten salt coolant in a riser space 130?, has a cylindrical containment vessel 134 with a reactor vessel 120?, at least two lobes 121, preferably three to nine lobes 121, each lobe 121 interconnected with the other lobe(s) and each containing a fast reactor core, 116?, 116?, 116? and 116??.

Abstract: A tertiary shutdown system for a liquid metal reactor that eliminates the need for considering an ATWS in setting the thermal power limits of the reactor. The shutdown system includes a reservoir of neutron absorber material that is sealed by a valve that may actively dispense the absorber upon operator command, into a stagnant pool of sodium in the core that is confined to prevent the absorber material from entering the coolant flowing through the core. Additionally, the valve may be passively open to release the absorber material into the stagnant pool of sodium when the temperature at the valve exceeds a predetermined limit.

Abstract: Passive emergency cooling in response to a loss of coolant accident (LOCA) in a PWR, having an integral reactor pressure vessel incorporating the steam generators and housed in a small high pressure containment vessel, is provided by circulating cooling water through the steam generators and heat exchangers in an external tank to cool the reactor vessel at a rate sufficient to lower the pressure in the reactor vessel below that in containment to reverse mass flow out of the reactor vessel and keep the reactor core covered without the addition of makeup water. Suppression tanks inside the small high pressure containment structure limit peak blowdown pressure in containment and provide flood-up water and gravity fed makeup water to cool the core. Diverse cooling is provided by natural circulation of air, and if needed, water, over the spherical containment structure.

Abstract: Passive emergency cooling in response to a loss of coolant accident (LOCA) in a PWR, having an integral reactor pressure vessel incorporating the steam generators and housed in a small high pressure containment vessel, is provided by circulating cooling water through the steam generators and heat exchangers in an external tank to cool the reactor vessel at a rate sufficient to lower the pressure in the reactor vessel below that in containment to reverse mass flow out of the reactor vessel and keep the reactor core covered without the addition of makeup water. Suppression tanks inside the small high pressure containment structure limit peak blowdown pressure in containment and provide flood-up water and gravity fed makeup water to cool the core. Diverse cooling is provided by natural circulation of air, and if needed, water, over the spherical containment structure.

Abstract: Hybrid combustion power systems comprising multiple direct energy conversion devices are disclosed, which devices (12, 14, 16) are preferably combined with a Rankine cycle containing a steam turbine (114), where combustion air (A) may be continuously preheated by an optional air heater (58), then by the waste heat of a low temperature direct energy conversion device (16) such as an alkali metal thermoelectric converter (AMTEC), and finally by the waste heat of a high temperature direct energy conversion device (12) such as an AMTEC, where the AMTECs include electrolyte (36) may include a condenser located in substantially the same geometrical plane as the AMTEC electrolyte (36) and thermally insulated from the electrolyte.

Abstract: Hybrid combustion power systems comprising multiple direct energy conversion devices are disclosed, which devices (12,14,16) are preferably combined with a Rankine cycle containing a steam turbine (114), where combustion air (A) may be continuously preheated by an optional air heater (58), then by the waste heat of a low temperature direct energy conversion device (16) such as an alkali metal thermoelectric converter (AMTEC), and finally by the waste heat of a high temperature direct energy conversion device (12) such as an AMTEC, where the AMTECs include electrolyte (36) may include a condenser located in substantially the same geometrical plane as the AMTEC electrolyte (36) and thermally insulated from the electrolyte.

Abstract: A unitary, transportable, assembled nuclear steam supply system (NSSS) with a lifetime fuel supply utilizes a fast or epithermal spectrum reactor core immersed in a pool of light water together with a plurality of steam generators through which the coolant is circulated by up to 100% natural circulation at full power, augmented by reactor coolant pumps also immersed in the pool. Redundant steam generators and reactor coolant pumps, together with the fast or epithermal spectrum reactor core and pool configuration, make it possible to operate the NSSS for 10 to 15 or more years without maintenance on the internals or refueling, thereby rendering the system proliferation resistant.

Abstract: A modular fuel assembly for a nuclear thermal engine includes a plurality of fuel elements each having a fueled, truncated conical shell and an unfueled peripheral lip at the base of the shell with radial passages there-through. The fuel elements are nested with the lips seating one on top of another to form a stack of fuel elements with frusto-conical flow passages between the shells of adjacent fuel elements which are divided into channels by ribs on the conical shells. The stack of fuel elements is mounted in a cylindrical housing with the bases of the shells facing a central inlet opening at one end of the housing. Propellant enters the central inlet opening, is deflected radially outward by a deflector into an annular flow distribution channel from which it flows radially inward through the passages in the fuel element lips, through the flow channels of frusto-conical passages between the fueled shells where it is heated, and out through a central exhaust passage.

Abstract: A method for reducing thermal striping in liquid metal fast breeder reactors by reducing temperature gradients between adjacent fuel and blanket assemblies by shuffling blanket assemblies at each refueling outage so as to progressively shuffle the blanket assemblies to the core periphery through multiple moves and to generally locate fresh blanket assemblies adjacent to exposed fuel assemblies and exposed blanket assemblies adjacent to fresh fuel. Additionally, assembly orificing is altered to provide less flow to blanket assemblies needing less flow due to an otherwise decreased temperature gradient and providing additional flow to fuel assemblies which need more flow to sufficiently reduce temperature gradients to prevent thermal striping.

Abstract: Operation of a liquid-metal-cooled fast-breeder reactor is enhanced by distributing coolant among the fuel assemblies at such a rate that the strain equivalent limiting temperature of each fuel assembly is closely approached but not exceeded. Further improvement is attained by proportionally allocating less coolant of a total prescribed coolant flow to the outer fuel assemblies of the reactor (yet satisfying the condition that the strain equivalent limiting temperature is not exceeded) whereby additional coolant flow is available for the inner fuel assemblies, thereby further reducing the radial thermal gradient in the coolant immediately above the fuel assemblies, a particular advantage being that the temperature of the upper internal structure of the reactor immediately above the inner zone of the reactor is reduced.