A traveling wave nuclear fission reactor, fuel assembly, and a method of controlling burnup therein. In a traveling wave nuclear fission reactor, a nuclear fission reactor fuel assembly comprises a plurality of nuclear fission fuel rods that are exposed to a deflagration wave burnfront that, in turn, travels through the fuel rods. The excess reactivity is controlled by a plurality of movable neutron absorber structures that are selectively inserted into and withdrawn from the fuel assembly in order to control the excess reactivity and thus the location, speed and shape of the burnfront. Controlling location, speed and shape of the burnfront manages neutron fluence seen by fuel assembly structural materials in order to reduce risk of temperature and irradiation damage to the structural materials.

A self-regulating inherently safe apparatus for generating neutrons is described herein that includes a reaction chamber that sustains neutron generation when filled with a liquid fissionable material and an expansion chamber that dampens neutron generation from the liquid fissionable material in response to expansion of the liquid fissionable material into the expansion chamber. Consequently, the apparatus may substantially dampen neutron generation for operating temperatures above a nominal operating temperature without requiring active or external control and inherently limit neutron generation to a maximum desired output power. Also described herein is a self-regulating system and corresponding method for extracting energy from fissionable material that includes a neutron generator that generates neutrons from a liquid fissionable material and a sub-critical collection of fissionable material that generates a non-sustaining plurality of fission events from neutrons received from the neutron generator.

A self-regulating inherently safe apparatus for generating neutrons is described herein that includes a reaction chamber that sustains neutron generation when filled with a liquid fissionable material and an expansion chamber that dampens neutron generation from the liquid fissionable material in response to expansion of the liquid fissionable material into the expansion chamber. Consequently, the apparatus may substantially dampen neutron generation for operating temperatures above a nominal operating temperature without requiring active or external control and inherently limit neutron generation to a maximum desired output power. Also described herein is a self-regulating system and corresponding method for extracting energy from fissionable material that includes a neutron generator that generates neutrons from a liquid fissionable material and a sub-critical collection of fissionable material that generates a non-sustaining plurality of fission events from neutrons received from the neutron generator.

A nuclear reactor comprising: a moderator including a metal hydride; and a nuclear fuel in which europium is added as an additive to a main nuclear fuel material. Thus, the nuclear reactor can be kept in the subcritical state even under the state where all the control devices are pulled out before startup.

A closed-vessel molten salt reactor (cvMSR) is described herein. A cvMSR may comprise a suspended container, such as a metallic container, within a trench surrounded by a concrete enclosure and a concrete cover having a number of channels. The container is rotatable between different orientations. The container may be hollow and a solution of fissile materials and salt materials may be provided within the container. The solution may be capable of undergoing a chain reaction nuclear fission process once a threshold temperature is reached. Heat generated by the solution may heat a fluid surrounding the container. The heated fluid may be transported, through the number of channels of the concrete cover, to an external location where the heated fluid may be used in distributing heat and/or electricity generation.

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.

Exemplary embodiments provide automated nuclear fission reactors and methods for their operation. Exemplary embodiments and aspects include, without limitation, re-use of nuclear fission fuel, alternate fuels and fuel geometries, modular fuel cores, fast fluid cooling, variable burn-up, programmable nuclear thermostats, fast flux irradiation, temperature-driven surface area/volume ratio neutron absorption, low coolant temperature cores, refueling, and the like.

The present invention provides a small nuclear power generation system being safe and easily controlled by load following, and allowing reductions in manufacturing costs and maintenance and management costs. The small nuclear power generation system has a small nuclear reactor employing a load following control method. The reactor includes: a fuel assembly reactor core 4 having metallic fuel containing one or both of uranium (235, 238) and plutonium-239; a reactor vessel 1 containing the fuel assembly reactor core 4; metallic sodium loaded into the reactor vessel 1 and heated by the fuel assembly reactor core 4; and a neutron reflector 2 for achieving criticality in the reactor core with effective multiplication factor of neutrons emitted from the fuel assembly reactor core 4 being maintained at or above about 1. The load following control method of the reactor allows a neutron effective multiplication factor to be controlled by coupling the neutron reflector to spring or spiral metallic members and utilizing heat deformation in the metallic members due to the temperature in coolant metallic sodium to control the fast neutron reflection efficiency of the neutron reflector

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.