Cores include different types of control cells in different numbers and positions. A periphery of the core just inside the perimeter may have higher reactivity fuel in outer control cells, and lower reactivity cells may be placed in an inner core inside the inner ring. Cores can include about half fresh fuel positioned in higher proportions in the inner ring and away from inner control cells. Cores are compatible with multiple core control cell setups, including BWRs, ESBWRs, ABWRs, etc. Cores can be loaded during conventional outages. Cores can be operated with control elements in only the inner ring control cells for reactivity adjustment. Control elements in outer control cells need be moved only at sequence exchanges. Near end of cycle, reactivity in the core may be controlled with inner control cells alone, and control elements in outer control cells can be fully withdrawn.

An in-vessel fuel transfer machine may be permanently affixed to a nuclear reactor and remain in place during power operations. The in-vessel fuel transfer machine may include a pantograph machine that positions a grapple in order to access any fuel socket location within the core and move any of the core assemblies between the core, an in-vessel fuel storage area, and a fuel elevator. The grapple may be positioned through a combination of movements, such as, rotating a rotating plug assembly, rotating the in-vessel fuel transfer machine, extending the pantograph arms, and shuttling the grapple along a leg. The grapple may be compliant to accommodate deformed core assemblies and may be configured to pivot to more closely align to an eccentric core assembly handling socket or be moveable in a horizontal plane to accommodate a deformed core assembly during insertion or withdrawal.

An advanced initial core fuel configuration is for improving the fuel management efficiency and thus economics for a nuclear reactor. The advanced initial core fuel configuration includes a plurality of fuel assemblies having different average enrichments of uranium 235 and arranging the fuel assemblies in an initial core configuration structured to emulate a known equilibrium reload cycle core at least in terms of spatial reactivity distribution. The resulting average enrichment within the initial core ranges from below about 1.0 percent weight of uranium 235 to about 5.0 percent weight of uranium 235. An advanced lattice design is also disclosed.

There is provided a core of a boiling water reactor that can be operated without loading a new fuel assembly at an operation cycle before decommissioning. In the core of the boiling water reactor in which multiple fuel assemblies are loaded in a square lattice shape, during the fuel exchange, dispositions of the multiple fuel assemblies loaded into the core are changed without loading a new fuel assembly in the core, based on the number of residence cycles, in the core, of fuel assemblies laterally adjacent and longitudinally adjacent to a fuel assembly having the shortest loading period in core cross section and the number of residence cycles, in the core, of fuel assemblies diagonally adjacent thereto, among fuel assemblies loaded into the core after the fuel exchange without loading a fuel assembly having a shorter loading period than a fuel assembly having the shortest loading period loaded into the core before the fuel exchange in the core after the fuel exchange.

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.

A nuclear component transfer device that incorporates a shielded canister into the mast design of a conventional nuclear refueling machine. A moveable mast telescopes within a stationary mast which is attached to a bridge for lateral positioning. The canister allows for the addition of shielding that is positioned with the movement of the moveable mast without additional motorized components to deploy the shielding during nuclear component movement. The nuclear component is drawn up into the shielded canister as the moveable mast lifts the nuclear component. The nuclear component is then placed into a transfer cart that is also fitted with a shielded canister. The transfer is made without exposing the nuclear components resulting in completely shield movement.

Illustrative embodiments provide methods and systems for migrating fuel assemblies in a nuclear fission reactor, methods of operating a nuclear fission traveling wave reactor, methods of controlling a nuclear fission traveling wave reactor, systems for controlling a nuclear fission traveling wave reactor, computer software program products for controlling a nuclear fission traveling wave reactor, and nuclear fission traveling wave reactors with systems for migrating fuel assemblies.

A rod transfer assembly has an outer rotating plug. A pick-up arm assembly extends from the outer rotating plug and includes a pivoting arm. An inner rotating plug is disposed off-center from and within the outer rotating plug and is rotatable independent of a rotation of the outer rotating plug. An access port rotating plug is disposed off-center from and within the inner rotating plug and is rotatable independent of rotation of the outer and inner rotating plugs. A pull arm extends from the access port rotating plug.

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 method of the plug and removable block extraction when reloading the nuclear reactor. The invention relates to nuclear engineering, in particular to a process of the plug and the removable block extraction from a fast reactor with a heavy liquid metal coolant. The technical result consists in extracting the plug and the removable block without fuel assemblies from the nuclear reactor using a complex of handling equipment under radiation safety conditions. The method of the plug removable block extraction involves preliminary installation of handling equipment, removing the plug from the reactor monoblock, as well as transportation and positioning of the plug in the plug shaft, unloading the removable block, its transportation and placing the removable block in the shaft for the removable block disassembly.