Abstract: A nozzle for joining a pool of water to a nuclear reactor pressure vessel includes a tubular body having a proximal end joinable to the pressure vessel and a distal end joinable in flow communication with the pool. The body includes a flow passage therethrough having in serial flow communication a first port at the distal end, a throat spaced axially from the first port, a conical channel extending axially from the throat, and a second port at the proximal end which is joinable in flow communication with the pressure vessel. The inner diameter of the flow passage decreases from the first port to the throat and then increases along the conical channel to the second port. In this way, the conical channel acts as a diverging channel or diffuser in the forward flow direction from the first port to the second port for recovering pressure due to the flow restriction provided by the throat.

Abstract: A head for closing a nuclear reactor pressure vessel shell includes an arcuate dome having an integral head flange which includes a mating surface for sealingly mating with the shell upon assembly therewith. The head flange includes an internal passage extending therethrough with a first port being disposed on the head mating surface. A vent line includes a proximal end disposed in flow communication with the head internal passage, and a distal end disposed in flow communication with the inside of the dome for channeling a fluid therethrough. The vent line is fixedly joined to the dome and is carried therewith when the head is assembled to and disassembled from the shell.

Abstract: A nuclear reactor vessel cavity seal plate. An annular support plate is positioned over the cavity between the reactor vessel and the shield structure. The inner diameter of the support plate rests freely upon the reactor vessel flange to allow movement of the vessel thereunder during thermal expansion and contraction. A flexible annular seal positioned over the support plate has its inner diameter seal welded to the reactor vessel flange and its outer diameter seal welded to the shield structure. Matching ports in the support plate and seal provide access to nuclear instruments below the support plate. A mounting block around each port accepts a cover plate that seals the port. This provides a permanent seal plate that allows flooding of the cavity for refueling with it only being necessary to remove the cove plates for normal reactor operations.

Abstract: A liquid metal cooled nuclear reactor for a nuclear power plant on the modular principle is disposed in a reactor cavern having cooling surfaces. A reactor tank contains a reactor core and one or more heat exchangers and primary pumps and is surrounded by a double tank of nodular graphite cast iron serving as a heat accumulator and having a plurality of detachably interconnected and superposed rings and a base. With this configuration, not only is the structure simplified but advantages are also achieved for operation, inspection and repair or exchange. Producing the double tank from cast iron has appreciable advantages for the construction of the entire plant with respect to external influences. The function as a heat accumulator has appreciable advantages for the construction of the heat removal systems of the cooling surfaces.

Abstract: A prestressed pressure vessel safety enclosure is used as a pressure safety enclosure for a nuclear reactor pressure vessel or other primary system vessel containing fluid or gaseous material under high pressure, such as, steam generators, pressurizers and pumps. The special pressure vessel enclosure comprises a first pressure vessel containment assembly surrounding the primary pressure vessel. A pair of first upper and lower pressure vessel jackets are adapted to enclose and be spaced apart, respectively, from the upper and lower portions of the first pressure vessel containment assembly with the rims of the jackets adapted to be slidable and sealed with respect to the first pressure vessel containment assembly. The spaces between the jackets and pressure vessel containment assembly are filled with a high boiling point, low melting point metal.

Abstract: A pressure control chamber of a reactor containment vessel for receiving the atmosphere of the reactor containment vessel containing leakage steam developing in the event of an accident includes a pressure control pool, and a wet well disposed above the pressure control pool. The wet well is divided into an inner peripheral portion and an outer peripheral portion. The inner and outer peripheral portions are communicated with each other via the pressure control pool. An outlet port for flowing the atmosphere of the reactor containment vessel containing the leakage steam is provided at the inner peripheral side of the pressure control pool. When the atmosphere of the reactor containment vessel containing the leakage steam is introduced into the pressure control pool in the event of the accident, this atmosphere is condensed by the water in the pressure control pool, and the gas of this atmosphere not condensed is accumulated in the inner peripheral portion of the wet well.

Abstract: Inlet nozzles for a gravity-driven cooling system (GDCS) are forged with a cylindrical reactor pressure vessel (RPV) section to which a support skirt for the RPV is attached. The forging provides enhanced RPV integrity around the nozzle and substantial reduction of in-service inspection costs by eliminating GDCS nozzle-to-RPV welds.

Abstract: A permanent pool seal and neutron shield 30 for providing an effective water barrier over the annular space 28 between a nuclear reactor vessel flange 24 and a surrounding annular ledge 22 includes annular deck sections 32 supported on spaced ribs 46.Flexible membranes 50,52 on the deck section peripheries accommodate relative movement. Openings 42, each with a removable plug structure which includes cover 44 and tapered can 60, provide vessel cavity 14 with ventilation and maintenance access. All cans 60 and similar containers 56 and 59 under the deck structure and flange 24 contain a shielding material 58 in the form of a boron-containing concrete. Supported below the cans is refractory insulating material 54.

Abstract: A multiple shell pressure vessel is fabricated in modular sections comprising a top head module, a nozzle course module and a bottom shell module, each module utilizing telescoping shells with filled interspaces, each shell being removable for inspection and repair with all modular sections and shells being held in compression by a pair of upper and lower single or multilayer tendon skirts held in place by a number of tension members in combination with hydraulic or mechanical jacks or rams. Both tendons and rams are located outside the pressure vessel. Included is a method of arranging the shell flanges and shell radial supports to reduce or eliminate torsional forces on the flanges and flange seals. A leak detection system monitors for leaks in all shells. A method of adjusting shell stresses during operation uses pumps to adjust the pressure of the filler material in the interspaces between shells.

Abstract: A nuclear power plant that is of a walk-away type with an encapsulated reaction core in a glass matrix pool having a reactive Thorium/U.sup.233 composition in a containment structure that radiates thermal energy for use in a closed gas cycle with a split path having a common compressor with an output that divides into a first path communicating with the thermal source and a second path communicating with an intercooler, the two paths combining in a turbine with an expander that discharges to a common collector for return to the compressor.

Abstract: The improvement in a nuclear reactor having a calandria tank containing moderator and a plurality of coolant flow channels which penetrate through the calandria tank and are loaded with fuel assemblies, the moderator and the coolant being isolated from each other. The improvement is constituted by a pressure container surrounding the outside of the calandria tank, a gap between the calandria tank and the pressure container being charged with the coolant; a recirculation pump for recirculating the coolant through the coolant flow channels; and a steam separator which is positioned inside the pressure container and separates the coolant flowing through the coolant flow channels into steam and water; whereby an improved nuclear reactor having a unitary pressure container structure is constructed.

Abstract: A vessel comprising a shell of large thickness, for example between 200 and 300 mm, consists of unit components symmetrical in revolution (2a, 2b, 6, 7, 8, 9, 10, 3a, 3b) and connected together by end-to-end welding. The components are made of a steel containing 2 to 2.50% of chromium, 0.9 to 1.1% of molybdenum and less than 0.15% of carbon. The welding for connecting these unit components is performed by means of an electron beam in a single pass over the entire thickness of the components, without filler metal. the invention applies particularly to the manufacture of a vessel for a pressurized-water nuclear reactor.

Abstract: The reactor vessel thread protector is a metal cover that is placed over the exposed stud, nut and washer projecting above the closure head to protect the threads from accidental corrosive leakage impingement emitted from mechanical seals on the top of the reactor vessel head. The stud protector includes a drip pan to collect any such fluid being emitted from the reactor vessel. Additionally, the reactor vessel stud thread protector will provide protection from accidental deformation to a stud due to operator maintenance around adjacent studs. The reactor vessel stud thread protector can be in the form of a cylinder which would cover a single stud bolt or a curved box having a rectangular cross-section that would cover a plurality of stud bolts.

Abstract: Gas-cooled high-temperature nuclear reactor having a reactor core comprising individual fuel elements provided with means for forming a barrier against the release of fission products producible therein during reactor operation, the fuel elements being received in a cylindrical barrel formed of an inner graphite layer functioning as a reflector, an outer layer of insulating material surrounding the inner layer, and a metallic receptacle, the inner and outer layers and the receptacle being formed of respective side, bottom and cover portions, the side and cover portions of the inner layer being formed with first channels into which means for controlling the reactors are insertable, the bottom, side and cover portions of the inner layer being further formed with second channels wherein, during reactor operation, cooling gas is circulated under pressure from the bottom to the top of the receptacle, the bottom portion of the inner layer having first openings for introducing cooling gas into the second channels du

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 multiple shell pressure vessel utilizes a number of spaced apart, concentrically disposed pressure vessel shells within and spaced apart from an outer pressure vessel shell, the spaces between each shell being filled with a low melting point, high boiling point material selected from the group, lead, tin, antimony, bismuth, or sodium and potassium, and mixtures thereof and subjected to a pressure whereby the innermost pressure vessel shell wall is maintained in compression while the main vessel is pressurized. Chemical compositions or compounds which contain boron or cadmium may also be added to the filler material. The vessel may include devices for keeping the pressure in the space between the innermost pressure vessel shell and the next innermost shell at a fixed predetermined multiple of the pressure within the innermost pressure vessel shell.

Abstract: A single loop nuclear power plant with a helium cooled high temperature reactor for generation of electric current, designed for a capacity of 1-5 MWe. The plant, which in addition to the high temperature reactor includes a gas turbine assembly and a heat exchange apparatus, is housed in two pressure vessels located above each other and connected in a releasable manner. The lower pressure vessel contains the high temperature reactor and is charged with the primary gas. The other circulation components are located in the upper pressure vessel which is filled with a protective gas. The gas turbine, the radiators, the high temperature compressor, the intermediate radiators, and the low pressure compressor, are arranged above each other in this sequence and aligned with the high temperature reactor. the recuperator is laterally arranged. A generator may also be located in the upper pressure vessel or in a container set upon the upper pressure vessel.

Abstract: The invention relates to a nuclear power station for a gas cooled high temperature pebble bed nuclear reactor. The nuclear power station is characterized by a combination of features, whereby the system inherent properties of a high temperature reactor are utilized to make possible the economical operation of a nuclear power station of medium capacity (300-600 MW.sub.el) while maintaining a high standard of safety. The characteristics comprise a reactor protection building equipped with pressure relief means in combination with filters, several auxiliary cooling systems separate from the operating cooling systems for the removal of decay heat in the case of accidents, and the utilization of a liner cooling system for the prestressed concrete reactor pressure vessel to assure the removal of the decay heat in case of a failure of the auxiliary cooling systems.

Abstract: Container system for a high-temperature nuclear reactor, including an outer metallic pressure vessel having an inwardly-protruding flange, an inner metallic core barrel resting tightly on the flange, and means disposed below the flange at a lower end of the core barrel for feeding and discharging cooling fluid, the core barrel being gas-tight above the flange.

Abstract: A pressurized nuclear water reactor has a substantially cylindrical flow liner with a cylindrical wall section and bottom and an open top. A barrel forms a riser chamber that contains the core in the flow liner. A pressure vessel contains the cylindrical flow liner to form a second annular chamber therebetween that contains a supplementary liquid coolant, with insulation means to provide a major portion of the supplementary liquid coolant at a first temperature and a minor portion thereof at a second higher temperature. Upon depressurization in the vessel, fluid communication means enable injection of supplementary liquid coolant from the second annular chamber into the core upon flashing of a minor portion to vapor. A further pool of water outside the pressure vessel, and insulation on the wall, maintain the desired temperature in the supplementary liquid coolant supply. Injection or removal of borated solution, as a chemistry control solution, into or from the supplementary liquid coolant is provided.

Abstract: A modular lining for adapting the containment to the core of a pressurized water nuclear reactor, consisting of juxtaposed modular blocks (5) placed between the core containment (1) and the outer surface of the core (3). Arranged between the adjacent faces of the blocks (5), there are thin packing pieces (8) maintaining a certain gap between the undrilled solid blocks (5). The blocks (5) are fixed non-contiguously to the core containment (1) by screw devices (10) cooled by water circulation. The invention applies in particular to pressurized water nuclear reactors of improved efficiency and with a varying neutron spectrum.

Abstract: An improved liquid metal nuclear reactor construction has a reactor core and a generally cylindrical reactor vessel for holding a large pool of low pressure liquid metal coolant and housing the core within the pool. The reactor vessel has an open top end, a closed flat bottom end wall and a continuous cylindrical closed side wall interconnecting the top end and bottom end wall. The reactor also has a generally cylindrical concrete containment structure surrounding the reactor vessel and being formed by a cylindrical side wall spaced outwardly from the reactor vessel side wall and a flat base mat spaced below the reactor vessel bottom end wall. A central support pedestal is anchored to the containment structure base mat and extends upwardly therefrom to the reactor vessel and upwardly therefrom to the reactor core so as to support the bottom end wall of the reactor vessel and the lower end of the reactor core in spaced apart relationship above the containment structure base mat.

Abstract: Nuclear reactor with a radiation-emitting core including a container for conducting a coolant, the radiation-emitting container having a wall formed with a plurality of slots disposed parallel to one another, the slots having a depth within the wall equal to at least one-fourth the thickness of the wall, the slots being spaced from one another a distance which is at most as great as the depth thereof.

Abstract: Liquid metal-cooled nuclear reactor incorporating a main vessel sealed by a slab and containing the reactor core, an inner vessel placed within the main vessel and defining in the latter a hot zone filled with relatively hot liquid metal and a cold zone filled with relatively cold liquid metal, at least one pump for circulating the liquid metal between the cold zone and the hot zone across the core and at least one heat exchanger disposed between the hot zone and the cold zone, wherein the inner vessel comprises two truncated cone-shaped ferrules opposed by their large bases and a small diameter cylindrical ferrule extending the small base of the upper truncated cone-shaped ferrule, the reactor core resting on the small base of the lower truncated cone-shaped ferrule by means of a support structure, the hot zone being formed within the inner vessel, while the cold zone is formed between the main vessel and the inner vessel.

Abstract: A nuclear reactor is provided with novel composite assemblies at selected locations at the periphery of the reactor core in order to reduce the rate of radiation exposure to a critical pressure vessel weld. The composite assemblies include a shield zone at a selected location close to the weld and a fuel zone incorporating fissile material. This approach reduces the rate of radiation exposure at at the weld while also contributing to production of power by the core.

Abstract: A concrete pressure vessel (1) for a nuclear reactor is formed with an arch (6) arranged above the cover (4) of the pressure vessel, said arch having a horizontally directed opening permitting horizontal transport of the cover. The cover (4) is retained by a plurality of compressive force transmitting elements (11) arranged between the cover and the arch (6).

Abstract: A self-contained modular nuclear reactor which can be prefabricated at a factory location, nuclear-certified at the factory, transported to a field location for final assembly and connection to a large-scale electric-power generating facility. The modular reactor includes a prefabricated nuclear heat supply module and a plurality of shell segments which can be assembled about the heat supply module and which provide a form for the pouring and curing of a cementatious biological shield about the heat supply module. The modular reactor includes passive shutdown heat removal systems sufficient to render the reactor safe in an emergency. A large-scale power plant arrangement is disclosed which incorporates a plurality of the modular reactors.

Abstract: A nuclear reactor in which the space between a reactor vessel and a guard vessel disposed outside the reactor vessel is kept in a pressurized, sealed state. The sealed space and the space outside the guard vessel are communicate only through a liquid manometer structure, which is kept sealed with liquid.

Abstract: To enable the benefits to be obtained simultaneously of using cast iron as a major constituent and of using helical prestressing, the cylindrical wall structure of a pressure vessel (which may be for a nuclear reactor) is made of truncated wedge shaped cast-iron slabs (the wedge faces of the slabs lying in radial planes of the wall structure and mutually adjacent slabs abutting one another in those planes, with a plurality of such slabs forming an annular assembly and a plurality of such assemblies stacked coaxially to form the cylindrical wall structure), the slabs having cast-in through passages, disposed obiquely, both right and left-handed in alternate layers at progressively increasing radial distance with respect to the cylindrical wall structrue, and the passages of one slab in alignment with the ends of passages of adjacent slabs in the same annular assembly and in the annular assemblies stacked adjacent thereto to provide in the assembled cylindrical wall structure a system of right- and left-handed