Abstract: The present invention is to provide a reactor core that allows a nuclear plant to continuously operate for a long term period, for example 15 years or longer, without requiring any fuel exchange, reduces the duration and number of maintenance steps involved in regular plant inspections, markedly improves plant availability and economic efficiency, and is effective in terms of nuclear nonproliferation. A plurality of fuel assemblies 103, themselves obtained by arranging fuel rods 100 and water rods 107 in square lattices, are arranged in a square lattice at a certain pitch. The blades 102a of a cross-shaped (cruciform) control rod 102 in a cross section are inserted into four adjacent spaces formed by four fuel assemblies 100 facing each other. A value of 0.

Abstract: The present invention provides a boiling water reactor nuclear power plant in which a reactor core support plate, upper grid plate, and a reactor core consisting of fuel assemblies supported by these plates are provided in the inner base portion of a nuclear reactor pressure vessel. Control rod guide tubes and a reactor core shroud are positioned over the upper grid plate, and a control rod drive mechanism is provided further above same, whereby the control rods can be inserted from above the reactor core, and natural circulation of cooling water inside the reactor can be achieved by means of a chimney effect of the control rod guide tubes. According to the above structure, there can be provided a compact and economical nuclear power plant.

Abstract: A core inlet structure for coolant disposed in a reactor pressure vessel of a boiling water reactor includes a core support plate provided with a plurality of fuel support holes, a reinforcing beam supporting the core support plate, a plurality of control rod guide pipes standing perpendicularly and having upper end portions fitted to the fuel support holes, and a fuel support member inserted into upper end portions of the control rod guide pipes and supported by the core support plate so as to support lower end portions of fuel assemblies. An inlet orifice is formed to the fuel support member so as to adjust flow rate of a coolant flowing in the fuel assemblies, and a vortex control structure is provided for the inlet orifice or provided at a portion on a coolant upstream side of the inlet orifice.

Abstract: The present invention provides a boiling water-type nuclear power plant comprising: a passive safety system having depressurization valves and a gravity driven core cooling system as an emergency core cooling system; a passive containment vessel cooling system in which reactor steam released in the containment vessel is cooled by a heat exchanger in a cooling water pool installed in the upper portion of the containment vessel; and a containment vessel flooding system which injects cooling water into a dry well of the containment vessel on an accident; wherein a containment vessel spray cooling system for injecting cooling water into the containment vessel via a pump is further added as a safety system.

Abstract: The present invention provides a boiling water reactor nuclear power plant in which a reactor core support plate, upper grid plate, and a reactor core consisting of fuel assemblies supported by these plates are provided in the inner base portion of a nuclear reactor pressure vessel. Control rod guide tubes and a reactor core shroud are positioned over the upper grid plate, and a control rod drive mechanism is provided further above same, whereby the control rods can be inserted from above the reactor core, and natural circulation of cooling water inside the reactor can be achieved by means of a chimney effect of the control rod guide tubes. According to the above structure, there can be provided a compact and economical nuclear power plant.

Abstract: The present invention is to provide a reactor core that allows a nuclear plant to continuously operate for a long term period, for example 15 years or longer, without requiring any fuel exchange, reduces the duration and number of maintenance steps involved in regular plant inspections, markedly improves plant availability and economic efficiency, and is effective in terms of nuclear nonproliferation.

Abstract: A separator/injector having an outlet pressure higher than an inlet pressure thereof is introduced instead of the dynamic equipment for a reactor recirculation system that is necessary in the prior art, to achieve both liquid-vapor separation and forced circulation. A jet pump and a recirculation flow-rate control valve are provided in a lower portion of a downcomer portion of a reactor pressure vessel. A shroud head has a double-walled structure, a two-phase liquid-vapor flow that is flowing from a lower portion of the lower shroud head is accelerated by an accelerator nozzle of the separator/injector, and a liquid component of the thus-separated flow is increased in pressure and guided into a jet pump through a space formed between the double shroud heads.

Abstract: A water level gauge for a nuclear reactor includes heat conduction means for absorbing and conducting heat to the outside of the drywell, the heat being supplied to reference water head water inside a reference water head tube defining a reference water level inside a reference water level container, and to water inside a lower part pressure pipe connecting a nuclear reactor pressure vessel with a differential pressure detector. The water level gauge further includes heat exchanger for removing the heat. With this device, the water level of the nuclear reactor may be correctly detected even in the case of leakage accident of the coolant of the nuclear reactor.

Abstract: According to a level meter of this invention, a pressure corresponding to a fixed water level formed by means of a reference chamber and a vertical pipe is applied to one pressure inlet port of a differential pressure detector, and a pressure corresponding to a water surface or water level inside a container to be measured is applied to the other pressure inlet port of the differential pressure detector by means of a lower pipe. Then, the water level inside the container is measured through the difference between these two pressures, the density of water to generate the pressures to be applied to the differential pressure detector, and the density of steam inside the container and the reference chamber. Adiabatic jackets are attached to the peripheries of the vertical pipe and the lower pipe.