Abstract: A boiling water reactor includes a reactor building, a reactor cavity pool, a primary containment vessel, and a passive containment cooling system. The reactor building includes a top wall defining a penetration therein, a bottom wall, and at least one side wall, which define a chamber. At least a portion of the primary containment vessel is in the chamber. The passive containment cooling system includes a thermal exchange pipe including an outer pipe and an inner pipe. The outer pipe has a first outer pipe end and a second outer pipe end. The first outer pipe end is closed and in the primary containment vessel. The second outer pipe end is open and extends into the reactor cavity pool. The inner pipe has a first inner pipe end and a second inner pipe end, which are open. The second inner pipe end extends into the reactor cavity pool.

Abstract: A system for installing or removing a component of a nuclear reactor, such as a CRDM, includes a riser apparatus having a lift assembly structured to hold and support the component and a first drive assembly coupled to the lift assembly and structured to selectively move the lift assembly and the component along a length of the riser apparatus, and a transition cart movable along an under vessel area of the nuclear reactor and having a pivot mechanism, wherein the riser apparatus is selectively engageable with the pivot mechanism and the pivot mechanism is structured to selectively rotate the riser apparatus from a horizontal position to a vertical position. The riser apparatus may also include a second drive assembly structured to selectively move the riser apparatus relative to the transition cart in a direction parallel to a longitudinal axis of the riser apparatus.

Abstract: An apparatus admits gas into the primary coolant of a pressurized water nuclear reactor having a coolant loop for a liquid coolant, in particular water, to which hydrogen is to be added. The coolant loop preferably includes a volume control tank for the coolant as well as at least one high-pressure pump which admits coolant that has been extracted from the coolant loop back into the coolant loop again. An admission point for the hydrogen is located in a suction line on the suction side of the high-pressure pump. A measurement line on the pressure side of the high-pressure pump communicates with the volume control tank or with a dewatering system. A device for measuring the hydrogen content in the coolant is incorporated into the measurement line. The measuring device is connected through a control device to a control valve, with which the delivery of hydrogen to the admission point can be controlled. The gas admission apparatus assures a definite, precisely maintained hydrogen content in the coolant.

Abstract: Method and apparatuses are provided for removing thermal energy from a nuclear reactor, which are fault tolerant. The apparatus includes at least one heat pipe configured to absorb thermal energy produced by the nuclear reactor. In addition, the apparatus includes a first compartment thermally coupled to the at least one heat pipe. The first compartment is configured to contain a first gas. Furthermore, the apparatus includes a second compartment thermally coupled to the at least one heat pipe. The second compartment is configured to contain a second gas and configured to isolate the second gas from the first gas.

Abstract: A process for the treatment of radioactive graphite which includes the following steps: (i) reacting the radioactive graphite at a temperature in the range of from 250° C. to 900° C. with superheated steam or gases containing water vapor to form hydrogen and carbon monoxide; (ii) reacting the hydrogen and carbon monoxide from step (i) to form water and carbon dioxide; and (iii) reacting the carbon dioxide of step (ii) with metal oxides to for carbonate salts. The process enables radioactive graphite, such as graphite moderator, to be treated either in-situ or externally of a decommissioned nuclear reactor.

Abstract: A Critical Channel Power (CCP) enhancement system is provided for a pressurized fuel-channel-type water-cooled nuclear reactor of the type adapted to be refuelled on-line by the insertion and removal of fuel bundles onto and from of a plurality of said fuel channel assemblies, each of said fuel channel assemblies. A means is provided for interlocking fuel bundles into pairs having their fuel elements aligned, thereby lowering the hydraulic resistance in the fuel channel and enhancing CCP. The means for interlocking prevents misalignment of the paired bundles during their residence time inside the reactor due to continuous rocking and vibration of the fuel bundles exposed to very high coolant mass flow rate and misalignment due to axial separation of bundles impacting upon one another during fuelling operations.

Abstract: A nuclear reactor using gas as a primary coolant and a liquid as a moderator and/or reflector. Gas coolant flows through inlet passages around the outlet plenum to a distributor plate. The gas is directed between fuel element housing thimbles and fuel elements therein, through the fuel elements, and into the reactor outlet plenum. Fins on the thimble housings conduct heat to the gas from a liquid moderator circulating in the core. The use of a liquid moderator enhances safety, allows the fissile material and reactor mass to be reduced and eliminates problems associated with cooling of a solid moderator.

Abstract: A pressurized water nuclear reactor comprises a normally vertical main vessel externally duplicated by a confinement enclosure. The main vessel contains a simplified primary circuit essentially incorporationg the reactor core and an annular steam generator arranged in such a way that the circulation of water, pressurized once and for all during the sealing of the vessel, takes place by natural convection. All the auxiliary circuits, conventionally ensuring cooling on shut down of such a reactor are eliminated, said cooling being ensured by a special arrangement of the space formed between the vessel and the enclosure and by the fact that the latter is immersed in an external cooling liquid, no matter what the slope of the reactor. The shut down of fission reaction in the core is ensured by systems of absorbing elements and by the automatic displacement of part of the reflector in the case of a slope of the reactor.

Abstract: A method and apparatus for extending the life of a core of a water moderated nuclear reactor by spectral shift comprising the displacement of a portion of the moderator in the core by a gas having a low neutron cross-section during the initial stage of the life of the core and displacing the gas and replacing it with moderator during the latter part of the life of the core.

Abstract: Nuclear reactor with a hydrogen-containing liquid coolant loop having an expansion tank for the coolant, a high pressure pump having a suction side and feeding coolant taken from the loop back into the loop after purification, a line bypassing the expansion tank and being connected to the suction side of the high-pressure pump, and means for introducing hydrogen into a liquid-filled section of the loop on the suction side of the high-pressure pump, including a liquid jet compressor for transporting hydrogen into the coolant.