Systems enhance stand pipe alignment and security with braces docking to the stand pipes. A link connects pairs of braces so the braces and stand pipes docked thereby cannot move relative to each other when fully secured. Partially securing braces allows adjustment of the braces and distance between the same and thus stand pipe position. Fully securing the braces makes the entire system rigid without need for a tie bar. Braces and links can be installed and secured to the stand pipes and among each other at an axial position from above the stand pipes, so that overhead, simple tooling may be used. A crimp nut or other resilient connector may be used to secure the systems from that single dimension with simple tooling. Any number of braces, joining to any number of other braces, may be used in the system, and several systems may be used at various levels.

According to an embodiment, a core catcher has: a main body including: a distributor arranged on a part of a base mat in the lower dry well, a basin arranged on the distributor, cooling channels arranged on a lower surface of the basin connected to the distributor and extending in radial directions, and a riser connected to the cooling channels and extending upward; a lid connected to an upper end of the riser and covering the main body; a cooling water injection pipe open, at one end, to the suppression pool, connected at another end to the distributor; and chimney pipes connected, at one end, to the riser, another end being located above the upper end of the riser and submerged and open in the pool water.

A method and apparatus of limiting power of a boiling water nuclear reactor system includes a reactor pressure vessel, a reactor core disposed in the reactor pressure vessel, a core shroud surrounding the reactor core, a downcomer region disposed between an inner surface of the reactor pressure vessel and the core shroud, a steam line connected to an upper end of the reactor pressure vessel and a condenser system that receives steam from the reactor pressure vessel. A portion of the condenser system condensate is returned to the reactor pressure vessel of the boiling water reactor inside the core barrel above the core rather than into the downcomer. Returning the condensate in this way increases the effectiveness of an isolation condenser system or if the condensate is a portion of the feedwater from the main condenser it provides an effective means to regulate core flow and core power.

To more reliably supply cooling water to a reactor pressure vessel and a reactor containment vessel using a back-up building if a severe accident should occur, a boiling water type nuclear power plant includes a nuclear reactor building including a reactor containment vessel, and an external building, which is installed independently outside the nuclear reactor building and which has an anti-hazard property. The external building has a power source and an operating panel independent of the nuclear reactor building. The boiling water type nuclear power plant includes a water injection pump installed inside the external building, an alternative water injection pipe performing water injection at least on a reactor pressure vessel or the reactor containment vessel in the nuclear reactor building from the water injection pump, and a valve connected to the alternative water injection pipe, making it possible to perform alternative water injection if a severe accident occurs.

Controlled-debris elements inhibit the formation of a fibrous/particulate debris bed that unduly increases the pressure head loss through the perforated plates of strainers in a nuclear power plant emergency core cooling system. In a loss of cooling accident, pumps draw cooling water through the plates, which retain on their surfaces fibrous material in the circulating water to prevent it from reaching the pumps while permitting entrained particulate matter to pass through the perforations. The controlled-debris elements have a specific gravity substantially the same as the circulating water so they are entrained in the cooling water that is drawn toward the strainers and intimately intermix with the fibrous and particulate matter in the cooling water. The elements are configured to provide open structures in the bed formed on the plate surfaces to distribute fibers in the flow away from the surface and maintain cavities between the elements for the particulates.

A passive containment cooling and filtered venting system includes: an outer well; a scrubbing pool arranged in the outer well; a cooling water pool installed above the dry well and the outer well; a heat exchanger partly submerged in the cooling water; a gas supply pipe that is connected to the inlet plenum of the ruin of the heat exchanger at one end and connected to a gas phase region of the containment vessel at the other end; a condensate return pipe that is connected to the outlet plenum of the heat exchanger at one end, and connected to inside the containment vessel at other end; and a gas vent pipe that is connected to the outlet plenum of the heat exchanger at one end and is submerged in the scrubbing pool at other end.

A fuel assembly capable of linearizing change of an infinite multiplication factor of a fuel and flattening excess reactivity while increasing average fissile plutonium enrichment of a MOX fuel, and a reactor loaded with the fuel assembly can be provided. A fuel assembly includes first fuel rods containing Pu and not containing burnable poison, a second fuel rod containing uranium and burnable poison and not containing Pu, a water rod, and a channel box accommodating the first and second fuel rods and the water rod in a bundle. The second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in a horizontal section, N2<N1 (N2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged on the outermost periphery is N1 and the number of the second fuel rods arranged adjacent to the water rod is N2, and W2<N2+W0<W1 (W2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged without being vertically and/or horizontally adjacent to each other in the horizontal section is W0, the number of the second fuel rods arranged vertically and/or horizontally adjacent to only one second fuel rod in the horizontal section is W1, and the number of the second fuel rods arranged vertically and/or horizontally adjacent to two second fuel rods in the horizontal section is W2, of the second fuel rods arranged on the outermost periphery.

A core of a light water reactor has a plurality of fuel assemblies. The fuel assemblies include a plurality of fuel rods in which a lower end is supported by a lower tie-plate and an upper end is supported by an upper tie-plate. The fuel rods form plenums above a nuclear fuel material zone and have a neutron absorbing material filling zone under the nuclear fuel material zone. Neutron absorbing members attached to the upper tie-plate are disposed between mutual plenums of the neighboring fuel rods above the nuclear fuel material zone. The neutron absorbing members have a length of 500 mm and are positioned at a distance of 300 mm from the nuclear fuel material zone. Even if the overall core is assumed to become a state of 100% void, no positive reactivity is inserted to the core.

A core plate assembly for a boiling water reactor, and a method of performing work thereon are disclosed. The core plate assembly comprises a core plate having through-going apertures, and a beam structure comprising parallel first beams and parallel second beams being perpendicular to the first beams. The beams enclose a plurality of rectangular areas each enclosing four of the through-going apertures. Control rod guide tubes are aligned with a respective one of the through-going apertures. A transition pieces is received in a respective one of the control rod guide tubes, and has four passages for communicating with a respective fuel assembly. Each passage permits a coolant flow into the respective fuel assembly. A flow inlet is provided for the coolant into each passage. At least one of the flow inlets has a cross-sectional shape deviating from a circular shape.

Dry tube tooling systems can manipulate dry tubes in reactors without removing all fuel next to the tubes, saving considerable outage time and allowing fresh detectors and instrumentation to be installed throughout fuel shuffling. Bodies of the tooling fits through a top guide and secure to the same without completely surrounding the dry tube or requiring all nearby fuel to be removed. The tooling includes a retainer that moves to secure to the dry tube and vertically and/or horizontally move the same. The retainer can release or install the dry tube in a fixed core location through such movement. Dry tubes can thus be installed and/or removed by operating the tooling from a bridge or crane above the reactor. The movement of the retainer can be achieved by power or signals from the operators to move and grasp the dry tube in a desired manner.