The invention relates to nuclear engineering and more particularly to controlled reactor start-up. The invention addresses a secondary startup neutron source by creating additional safety barriers between the coolant and the source active part materials. The secondary startup neutron source is designed as a steel enclosure housing an ampule containing antimony in the central enclosure made of a niobium-based alloy unreactive with antimony, with a beryllium powder bed located between the antimony enclosure and the ampule enclosure. An upper gas collector, located above the ampule serves as a compensation volume collecting gaseous fission products. The ampule is supported by a reflector and a bottom gas collector. The gas collectors, reflector, ampule enclosure and washers are made of martensite-ferrite grade steel.

A neutron sealed source holds cermet wire sources, such as Californium-252/Palladium wires, in separate blind apertures within a stainless steel block. The stainless steel block is part of an inner encapsulation and includes blind apertures arranged in rotational symmetry for receiving the cermet wire sources. The cermet wire sources are separated from each other and the fission and decay heat is rejected through the stainless steel block.

A neutron sealed source holds cermet wire sources, such as Californium-252/Palladium wires, in separate blind apertures within a stainless steel block, The stainless steel block is part of an inner encapsulation and includes blind apertures arranged in rotational symmetry for receiving the cermet wire sources. The cermet wire sources are separated from each other and the fission and decay heat is rejected through the stainless steel block.

Illustrative embodiments provide nuclear fission igniters for nuclear fission reactors and methods for their operation. Illustrative embodiments and aspects include, without limitation, a nuclear fission igniter configured to ignite a nuclear fission deflagration wave in nuclear fission fuel material, a nuclear fission deflagration wave reactor with a nuclear fission igniter, a method of igniting a nuclear fission deflagration wave, and the like.

Illustrative embodiments provide nuclear fission igniters for nuclear fission reactors and methods for their operation. Illustrative embodiments and aspects include, without limitation, a nuclear fission igniter configured to ignite a nuclear fission deflagration wave in nuclear fission fuel material, a nuclear fission deflagration wave reactor with a nuclear fission igniter, a method of igniting a nuclear fission deflagration wave, and the like.

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 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.

The present invention is related to a Thorium Molten Salt Reactor (Th-MSR) using 100% non-radioactive Thorium fuel, composed of LiF+BeF.sub.2+ThF.sub.4 without containing any U-235. The Th-MSR is consisted of a reactor chamber, a fuel injector, a fuel reservoir, an in-line chemical extraction unit, a heat exchanger, a few KW electricity turbine generator and a condenser. A few KW nuclear power generation system is adopting the controlling devices comprised of a neutron flux sensor, a fuel injecting sensor, a thermal sensor and a power output sensor. A neutron generator with a high neutron flux of 10.sup.13 n/s is used. The high flux fast neutrons are slowing down into the thermal neutrons by the graphite moderators in the reactor for initiating the fission.