The present disclosure relates to reducing losses in the effective delayed neutron fraction during the operation of a reactor, making it possible to provide for a high efficiency of burning out of minor actinides, and also that of increasing the leak-tight integrity of the primary circuit and the reliability of the reactor. The above-mentioned technical result is achieved in an integral molten salt fast reactor with a circulating fuel composition, comprising a vessel with inlet and outlet secondary circuit pipelines and a connection pipe for initial filling and replenishment with molten salt coolant, heat exchangers of the primary/secondary circuit, a side reflector, an upper reflector and a lower reflector, a core with a shell, and a main circulation pipe, wherein the side reflector is made of sections between which the heat exchangers of the primary/secondary circuit are arranged such that they lie flush against the shell of the core.

Methods and systems for stabilizing spent fuel assemblies from sodium-cooled nuclear reactors using Zamak are described herein. It has been determined that there is a synergism between Zamak and sodium that allows Zamak to form thermally-conductive interface with the sodium-wetted surfaces of the fuel assemblies. In the method, one or more spent fuel assemblies are removed from the sodium coolant pool and placed in a protective sheath. The remaining volume of the sheath is then filled with liquid Zamak. To a certain extent Zamak will dissolve and alloy with sodium remaining on the fuel assemblies. Excess sodium that remains undissolved is displaced from the sheath by the Zamak fill. The Zamak is then cooled until solid and the sheath sealed. The resulting Zamak-stabilized spent fuel assembly is calculated to have sufficient internal thermal conductivity to allow it to be stored and transported without the need for liquid cooling.

A liquid metal cooled nuclear reactor incorporates a fully passive decay heat removal system with a modular cold source. The system which simultaneously ensure decay heat removal in a completely passive way from the moment an accident starts; heat removal through the primary vessel; and reduction in the risk of chemical interaction between sodium (or NaK) and the material acting as the final cold source. The presence of the final cold source provides an improvement over sodium/air or NaK/air exchangers that are used in the prior art.

A nuclear reactor includes a reactor container, a reactor core, a control drum assembly, a hot channel, a heat exchanger and a main pump. The reactor container contains a coolant; the reactor core is arranged at a lower middle part of the reactor container; the control drum assembly is arranged on an outer periphery of the reactor core, and includes control drums arranged at intervals along a peripheral direction of the reactor core; the hot channel is arranged in the reactor container and located above the reactor core. The hot channel has a bottom hermetically connected to the control drum assembly and a top hermetically connected to an inner top surface of the reactor container. The hot channel has a hot pool passage for the coolant to pass through. The heat exchanger is arranged in the reactor container and located on an outer periphery of the hot channel.

A reactor core includes an inner core region that extends in a vertical direction, and has a plurality of first fuel pins accommodating an inner core fuel; an outer core region that extends in the vertical direction, is arranged to surround the inner core region from an outer peripheral side, and has a plurality of second fuel pins accommodating an outer core fuel; and a sodium plenum provided above the inner core region and the outer core region, in which a dimension of the outer core fuel in the vertical direction is larger than a dimension of the inner core fuel in the vertical direction, and the position of a center of the outer core fuel in the vertical direction is higher than the position of a center of the inner core fuel in the vertical direction.

The invention relates to the nuclear energy field, including pressurized water reactor containment internal passive heat removal systems. The invention increases heat removal efficiency, flow stability in the circuit, and system reliability. The system has at least one cooling water circulation circuit comprising a heat exchanger inside the containment and including an upper and lower header interconnected by heat-exchange tubes, a riser pipeline and a downtake pipeline connected to the heat exchanger, a cooling water supply tank above the heat exchanger outside the containment and connected to the downtake pipeline, a steam relief valve connected to the riser pipeline and located in the water supply tank and hydraulically connected to the latter. The upper and lower header of the heat exchanger are divided into heat exchange tube sections on the assumption that: L/D≦20, L being the header section length, D being the header bore.

A nuclear reactor cooled by liquid metal incorporating a passive system for evacuation of the decay heat with a phase change material thermal reservoir and a removable thermally-insulating layer around the phase change material reservoir. A nuclear reactor incorporates an integral system that guarantees: totally passive evacuation of decay heat from the initial moment of the accident; evacuation of power via the primary containment vessel; the presence of a final cold source with a reservoir incorporating an integral exchanger divided into a plurality of parallel tubes between which a phase change material is inserted, the reservoir being surrounded by a thermally-insulating layer that can be detached in a passive manner in the event of reaching a predetermined threshold temperature.

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.

A conduit housing includes a top face, a pair of side faces disposed opposite each other and adjacent to the top face, a front side, and a rear side. The top face includes a plurality of vertical conduit ports arranged in a plurality of rows. The front side is positioned between the pair of side faces and defines a plurality of stepped faces. The rear side is disposed opposite the front side and adjacent the top face. The stepped faces include a plurality of downward faces and each of the plurality of downward faces defines a downward face plane. The stepped faces also include a plurality of upward faces, where each of the plurality of upward faces defines an upward face plane. Each upward face includes a plurality of pitched conduit ports.

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.