Abstract: A nuclear reactor controlled by moving a liquid fuel between a reservoir and chambers in the core is provided. No pumps or moving parts within the reactor vessel are needed to move the fuel. The control system moves the liquid fuel between the core and the reservoir by moving a separate control gas. It can monitor the internal state of the core through the control connections. The fuel chamber is shaped so that evolved gases escape the core and can be collected at the control connections. The core reverts to a safe state on power failure.

Abstract: Various embodiments of a transportable nuclear power generator having a plurality of subcritical power modules are disclosed. Each of the plurality of subcritical power modules includes a fuel cartridge, a power conversion unit, and a housing substantially enclosing the fuel cartridge and the power conversion unit. The fuel cartridge contains a nuclear fuel and has a proximal end and a distal end. The power conversion unit includes a compressor turbine disposed at the proximal end of the fuel cartridge and a power turbine disposed at the distal end of the fuel cartridge. At least one of the plurality of subcritical power modules is movable with respect to the other of the plurality of subcritical power modules between a first position and a second position to control criticality of the nuclear fuel contained in the fuel cartridges of the plurality of subcritical power modules.

Abstract: Nuclear fuels for nuclear reactors are described, and include nuclear fuels having a first fuel component of recycled uranium, and a second fuel component of depleted uranium blended with the first fuel component, wherein the blended first and second fuel components have a fissile content of less than 1.2 wt % of 235U. Also described are nuclear fuels having a first fuel component of recycled uranium, and a second fuel component of natural uranium blended with the first fuel component, wherein the blended first and second fuel components have a fissile content of less than 1.2 wt % of 235U.

Abstract: This invention relates to a MOX fuel assembly for PWRs that enables satisfactorily suppressing a power peaking factor without the necessity of reducing the Pu content per fuel assembly. The MOX fuel assembly has a lattice arrangement in which one or more burnable poison contained UO2 fuel rods and a plurality of MOX fuel rods are disposed in an n-rows by n-columns (n×n) lattice array. The MOX fuel rod consists of at least two kinds of MOX fuel rods including a plurality of first MOX fuel rods and a plurality of second MOX fuel rods. The first MOX fuel rod has a predetermined Pu content and a predetermined Pu weight, and the second MOX fuel rod has substantially the same Pu content as that of the first MOX fuel rod and a different Pu weight from that of the first MOX fuel rod.

Abstract: There is provided a semiconductor storage device and portable electronic equipment including a nonvolatile memory element that can easily be miniaturized. The semiconductor storage device includes a memory cell array 21 in which a plurality of memory elements 1 are arranged and a write state machine 32. The memory element 1 includes a gate electrode 104 formed on a semiconductor layer 102 via a gate insulator 103, a channel region arranged below the gate electrode 104, diffusion regions 107a, 107b that are located on both sides of the channel region and have a conductive type opposite to that of the channel region and memory function bodies 109 that are located on both sides of the gate electrode 104 and have a function to retain electric charge. The write state machine 32 can selectively prevent program and erase of data in the memory elements within a predetermined range.

Abstract: An improved method of increasing the power output of an existing nuclear power plant includes increasing the thermal power output of the plant's nuclear island and constructing of an auxiliary BOP to handle the increased thermal power. The thermal power of the nuclear island can be increased such as by increasing the thermal power of the plant's reactor, by replacing the plant's steam generator with one that is more efficient, and by increasing the flow rate and/or change in temperature of a coolant in a secondary cooling loop of the plant. The thermal power of the reactor can be increased such as by replacing existing cylindrical fuel rods with fuel rods having a relatively greater surface area to volume ratio and/or by increasing the flow rate and/or the change in temperature of a coolant of a primary cooling loop. The auxiliary BOP can be constructed while the plant is in operation, and can then be connected with the nuclear island during a maintenance operation on the reactor.

Abstract: According to the method, a reactor core is shut down during the operation cycle. One or more fuel bundles of the reactor core are then moved to new positions within the reactor core to increase a total energy, output of the reactor core as compared to continuing operation of the reactor core without the shutting down and moving steps.

Abstract: Seed-blanket type nuclear reactor cores are employed to burn thorium fuel with conventional reactor fuels, including nonproliferative enriched uranium, and weapons or reactor grade plutonium. In a first embodiment, the core is completely nonproliferative in that neither the reactor fuel, nor the generated waste material, can be used to manufacture nuclear weapons. In a second embodiment of the invention, the core is employed to burn large amounts of weapons grade plutonium with the thorium, and provides a convenient mechanism by which stockpiled weapons grade plutonium can be destroyed and converted into electrical energy. The cores of both embodiments are comprised of a plurality of seed-blanket unit fuel assemblies which have centrally located seed regions that are surrounded by annular blanket regions. The seed regions contain the uranium or plutonium fuel rods, while the blanket regions contain thorium fuel rods.

Abstract: A high conversion nuclear reactor core has fuel assemblies made up from large numbers of axially-extending uranium-plutonium mixed oxide fuel rods. The fuel rods are densely packed so as to give a high conversion ratio of fissile substances, preferably approaching unity. The average plutonium enrichment in the assemblies is higher in their bottom, upstream halves, than in their top downstream halves. This has the effect of reducing a potentially dangerously high void coefficient in the core.

Abstract: The present invention relates to nuclear reactors and more specifically to a fuel bundle arrangement for a boiling water nuclear reactor in which so-called mixed oxide fuels including plutonium and uranium are utilized in a nuclear fuel bundle together with a burnable absorber such as gadolinium to optimize the reaction of a nuclear fuel bundle.

Abstract: To provide intrinsic reactor safety, the fuel sub-assemblies of a nuclear reactor core are provided with reactivity control mechanisms operable, in response to temperature rises above desired limits, to interact with adjacent fuel sub-assemblies and effect radial dilation of the core in order to reduce reactivity. Various embodiments are disclosed in which differential thermal expansion of an operating device or devices (34; 40; 42, 44, 46; 50) is translated into radially outward displacement of a lever or levers (28) for contact with neighbouring sub-assemblies.

Abstract: A neutron reactivity control system for a LWBR incorporating a stationary seed-blanket core arrangement. The core arrangement includes a plurality of contiguous hexagonal shaped regions. Each region has a central and a peripheral blanket area juxapositioned an annular seed area. The blanket areas contain thoria fuel rods while the annular seed area includes seed fuel rods and movable thoria shim control rods.

Abstract: A reactor fuel assembly (15) configuration which allows cold shutdown margins to be met with minimal penalty to operating efficiency. The assembly comprises a component of fissile material distributed over a substantial axial extent of the fuel assembly and a component of neutron absorbing material having an axial distribution characterized by an enhancement in a relatively short axial zone (65) (the "cold shutdown control zone") corresponding to at least a portion of the axial region of cold shutdown maximum reactivity. The axial distribution of the component of neutron absorbing material typically is characterized by an additional enhancement in an axial zone (62) (the "hot operating control zone"). The component of neutron absorbing material is conveniently incorporated into at least some of the fuel rods (57-G1, G2, G3, G4). The enhancement in the cold shutdown control zone may be provided at least in part by one or more fuel rods (G2, G3) having absorber only in the cold shutdown control zone.

Abstract: A mechanical drive system (10) for moving alternate nuclear reactor fuel rods (14) within the nuclear reactor core (12) and relative to the remaining stationary nuclear reactor fuel rods (16) so as to axially displace the movable fuel rods (14), and enriched and natural uranium fuel zones defined therein, relative to similarly defined enriched and natural uranium fuel zones within the stationary fuel rods (16) in order to optimize utilization of excess or free neutrons produced within the nuclear reactor core within a fuel cycle. The nuclear reactor fuel rods (14, 16) all have a length which is less than that of standard-sized nuclear reactor fuel rods, and therefore, a plenum chamber (20) is able to be defined between an upper core plate (22) and an auxiliary upper core plate (24).

Abstract: The present invention relates to an installation for replacing a member in a contaminated fluid circuit. It also relates to a process for replacing this member.Installations for treating contaminated fluids, particularly radioactive fluids, comprise pipe systems in which the contaminated fluid flows. These systems or circuits have transfer, distribution, purification and cleaning members and the like, such as pumps, valves, filters, etc. These members are subject to wear, particularly when they have moving parts, and/or dirt or pollutants. It is therefore necessary to replace them by new members or overhaul them at intervals of varying length. Besides such replacements due to wear or pollution, it may be necessary to replace one member by another having different characteristics, e.g. one pump by another pump having different operating principles and/or flow rates.

Abstract: A core construction for a nuclear reactor having a multiplicity of fuel cells forming a core in which each fuel cell includes four fuel assemblies arranged in adjacent relationship and one control rod insertable into a position surrounded by the four fuel assemblies. The fuel cells includes first fuel cells each having a relatively high cell mean infinite neutron multiplication factor and including one fuel assembly containing a burnable poison, and second fuel cells each having a relatively low cell mean infinite neutron multiplication factor and including no fuel assembly containing a burnable poison. The first fuel cells are arranged both in a central zone of the core disposed within about one-half the core radius from the center of the core and in a circumferential zone of the core outside the central zone. The second fuel cells are arranged only in the central zone and no second fuel cells are arranged in the circumferential zone.

Abstract: An improved reactor and fuel assembly design is disclosed wherein a liquid moderated thermal reactor is initially run with all or a portion of its fuel assemblies in an undermoderated boiling water mode to take advantage of increased conversion ratio at lower H/fuel ratios, and after a suitable period of operation, the neutron spectrum for all or a portion of the undermoderated boiling assemblies is shifted to lower energies to increase reactivity by converting a number of fuel assemblies to a nearer optimum moderated pressurized or non-boiling mode. The increased reactivity allows for continued operation of the modified assembly. The improved reactor and fuel assembly design results in improved fuel utilization and neutron economy and reduced control requirements for the reactor. The design may be augmented by reducing the number of fuel rods comprising the assembly after a suitable period of operation, as disclosed in the applicants copending application filed Nov. 1, 1977, Ser. No. 847,524.