Abstract: In response to a change in a thermal operational parameter in a nuclear fission reactor, reactivity is controlled by driving a neutron absorption parameter modifying material to or from a region of the core of the nuclear fission reactor. The apparatus includes a driver material disposed in a first reservoir portion and a second reservoir portion of a first reservoir and connected by a first conduit. A high-Z material may be distributed in the driver material. The neutron absorption parameter modifying material is disposed in both a second reservoir and the second reservoir portion of the first reservoir. A portion of the neutron absorption parameter modifying material is in physical contact with a portion of the driver material in the second reservoir portion. The neutron absorption parameter modifying material is driveable by the driver material between the second reservoir portion and the second reservoir through a second conduit.

Abstract: Disclosed embodiments include a vented nuclear fission fuel module system. Given by way of non-limiting example and not of limitation, an illustrative vented nuclear fission fuel module system includes a nuclear fission fuel element capable of generating a gaseous fission product. A valve body is associated with the nuclear fission fuel element, and the valve body defines a plenum therein for receiving the gaseous fission product. A reclosable valve is in operative communication with the plenum for controllably venting the gaseous fission product from the plenum, and the valve body includes a flexible diaphragm coupled to the valve for moving the valve to a closed position.

Abstract: Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.

Abstract: Disclosed embodiments include methods of assembling a vented nuclear fission fuel module. Given by way of non-limiting example and not of limitation, an illustrative method of assembling a vented nuclear fission fuel module includes receiving a nuclear fission fuel element capable of generating a gaseous fission product. A valve body is coupled to the nuclear fission fuel element, and the valve body defines a plenum therein for receiving the gaseous fission product. A valve is disposed in communication with the plenum for controllably venting the gaseous fission product from the plenum. A flexible diaphragm is coupled to the valve for moving the valve. A cap is mounted on the valve, and a manipulator extendable to the cap for manipulating the cap is received.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.

Abstract: Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.

Abstract: Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: Illustrative embodiments provide a nuclear fission reactor, a vented nuclear fission fuel module, methods therefor and a vented nuclear fission fuel module system.

Abstract: A nuclear reactor has a containment vessel and a voided calandria space having a plurality of fuel channels therein. A chamber surrounding the calandria space is receptive of a light water moderator and a solid reflector in the chamber surrounds the calandria space. Each fuel channel has a solid fuel matrix having a plurality of coolant holes extending longitudinally therethrough and receptive of light water coolant, a pressure tube surrounding the fuel matrix and a calandria tube surrounding the pressure tube and forming a gap therebetween.