The present invention relates to a sintered nuclear fuel pellet wherein one or more consolidated bodies of a burnable absorber are inserted inside, wherein the one or more consolidated bodies of the burnable absorber do not include nuclear fuel which includes UO.sub.2, and the one or more consolidated bodies of the burnable absorber are inserted into a radially central region of the sintered nuclear fuel pellet, such that the one or more consolidated bodies are surrounded by the nuclear fuel pellet without being exposed to an outside of the sintered nuclear fuel pellet. The present invention can optimize the regulation of excess reactivity by optimizing the self-shielding and the burning speed of the burnable absorber using one or more consolidated bodies the burnable absorber.

The present invention relates to a sintered nuclear fuel pellet wherein one or more consolidated bodies of a burnable absorber are inserted inside, wherein the one or more consolidated bodies of the burnable absorber do not include nuclear fuel which includes UO.sub.2, and the one or more consolidated bodies of the burnable absorber are inserted into a radially central region of the sintered nuclear fuel pellet, such that the one or more consolidated bodies are surrounded by the nuclear fuel pellet without being exposed to an outside of the sintered nuclear fuel pellet. The present invention can optimize the regulation of excess reactivity by optimizing the self-shielding and the burning speed of the burnable absorber using one or more consolidated bodies the burnable absorber.

Disclosed is a nuclear fuel rod including at least one or more fuel pellets, a cladding tube surrounding the fuel pellets, and burnable absorber inside the cladding tube. The burnable absorber comprises a burnable absorber material and a cladding material surrounding the burnable absorber material. The burnable absorber has a disk shape, and the cladding material is an alloy comprising zirconium.

Disclosed is a nuclear fuel rod including at least one or more fuel pellets, a cladding tube surrounding the fuel pellets, and burnable absorber inside the cladding tube. The burnable absorber comprises a burnable absorber material and a cladding material surrounding the burnable absorber material. The burnable absorber has a disk shape, and the cladding material is an alloy comprising zirconium.

A fuel assembly, which linearizes change of an infinite multiplication factor of a fuel and flattens excess reactivity while increasing average fissile plutonium enrichment of a MOX fuel, and a reactor are provided. The fuel assembly includes first fuel rods containing Pu and not containing burnable poison, a second fuel rod containing uranium and burnable poison and not containing Pu, a water rod, and a channel box accommodating the first and second fuel rods and the water rod in a bundle. The second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in a horizontal section, and N2<N1 (N2 is a positive integer or zero) is satisfied where the number of second fuel rods arranged on the outermost periphery is N1 and the number of second fuel rods arranged adjacent to the water rod is N2.

A fuel assembly, which linearizes change of an infinite multiplication factor of a fuel and flattens excess reactivity while increasing average fissile plutonium enrichment of a MOX fuel, and a reactor are provided. The fuel assembly includes first fuel rods containing Pu and not containing burnable poison, a second fuel rod containing uranium and burnable poison and not containing Pu, a water rod, and a channel box accommodating the first and second fuel rods and the water rod in a bundle. The second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in a horizontal section, and N2<N1 (N2 is a positive integer or zero) is satisfied where the number of second fuel rods arranged on the outermost periphery is N1 and the number of second fuel rods arranged adjacent to the water rod is N2.

According to an embodiment, a design method for a light-water reactor fuel assembly comprises: accumulating a determined fuel data, showing that each of a combination of p.Math.n/N and e is feasible as the core or not, wherein N is a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the burnable poison, p is a ratio wt % of the burnable poison in the fuel, and e is an enrichment wt % of the uranium 235 contained in the fuel assembly; formulating a criterion formula which determines whether a combination of p.Math.n/N and e is feasible as a core or not and is formulated based on the determined fuel data; and determining whether a temporarily set composition of the fuel assembly is approved as a core or not based on the criterion formula.

According to an embodiment, a design method for a light-water reactor fuel assembly comprises: accumulating a determined fuel data, showing that each of a combination of p.Math.n/N and e is feasible as the core or not, wherein N is a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the burnable poison, p is a ratio wt % of the burnable poison in the fuel, and e is an enrichment wt % of the uranium 235 contained in the fuel assembly; formulating a criterion formula which determines whether a combination of p.Math.n/N and e is feasible as a core or not and is formulated based on the determined fuel data; and determining whether a temporarily set composition of the fuel assembly is approved as a core or not based on the criterion formula.

A nuclear reactor including a reactor core comprising a plurality of fuel materials and a plurality of heat pipes. The nuclear reactor further includes a heat exchanger coupled to the reactor core defining a flow path in an open volume including at least two heat pipes of the plurality of heat pipes. Methods of operating a nuclear reactor include passing fluid through an open volume in a heat exchanger including at least two heat pipes extending from a reactor core.

A low-power nuclear reactor includes a housing and a reflector forming a reactor core. The core includes inner and outer primary tubes therein, arranged together as bayonet tubes and intended for circulating a coolant, and secondary tubes, accommodating elements of a control and protection system. The reactor further includes an intake chamber for coolant of a primary loop, and a discharge chamber for coolant of the primary loop, separated by a partition. The outer primary tubes are secured on the intake chamber's bottom, and the inner primary tubes are secured on the partition. Fuel assemblies are mounted in the inner primary tubes on suspensions, which are mounted on the discharge chamber's upper portion. The secondary tubes are sealed off from the intake and discharge chambers for the coolant of the primary loop, and an inter-tube space of the core is filled with a medium or material transparent to neutrons.