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 provide a corrosion mitigation method for carbon steel pipe that can further reduce corrosion of the carbon steel pipe. In a BWR plant, oxygen is injected from an oxygen injection device 30 into a clean up system pipe 18 which is constituted by a Cr-containing carbon steel pipe containing Cr in a range of larger than 0.052 wt % and less than 0.4 wt % and being in communication with a RPV 3, and reactor water of 150 C. having a dissolved oxygen concentration of 30 g/L is generated. The reactor water is brought into contact with an inner surface of the clean up system pipe 18 to perform an oxidizing treatment on the inner surface, and an oxide film containing Cr is formed on the inner surface. Thus, after the oxide film is formed, hydrogen is injected into the reactor water in the RPV 3 through a water supply pipe 11 in communication with to the RPV 3, and even when the dissolved oxygen concentration in the reactor water in contact with the inner surface of the clean up system pipe 18 is reduced to 2 g/L, corrosion of the clean up system pipe 18 is remarkably mitigated.

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.

An operating floor confinement has an operating floor, a sidewall that surrounds the operating floor, a ceiling that is provided on an upper portion of the sidewall, a reactor well, a fuel pool, a dryer and separator pit, an equipment hatch that is provided on the sidewall, an air lock that is provided on the sidewall, and an isolation valve that is provided in a penetration line. The operating floor confinement forms a pressure boundary having pressure resistance and a leakage protection function. The operating floor confinement is separated from an equipment area of the reactor building and has no blowout panel.

When all fuel assemblies loaded in a region excluding an outermost periphery of the reactor core in an Nth operation cycle belong to the first fuel assembly, and all fuel assemblies loaded in the region excluding the outermost periphery of the reactor core in a (N+m) th (m>1) operation cycle belong to the second fuel assembly, the number of new loaded second fuel assemblies in the (N+m) th operation cycle is greater than the number of new loaded second fuel assemblies in a (N+m1) th operation cycle which is one operation cycle before the (N+m) th operation cycle, and a cycle burnup in the (N+m) th operation cycle is greater than a cycle burnup in the (N+m1) th operation cycle.

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.

The invention relates to SiC ceramic matrix composite (CMC) claddings with metallic, ceramic and/or multilayer coatings applied on the outer surface for improved corrosion resistance and hermeticity protection. The coating includes one or more materials selected from FeCrAl, Y, Zr and AlCr alloys, Cr.sub.2O.sub.3, ZrO.sub.2 and other oxides, chromium carbides, CrN, Zr- and Y-silicates and silicides. The coatings are applied employing a variety of known surface treatment technologies including cold spray, thermal spray process, physical vapor deposition process (PVD), and slurry coating.

Fuel assemblies include an outer channel having a physical configuration optimized for a position of the fuel assembly within a core of a nuclear reactor. The position of the fuel assembly with respect to an employed control blade in the nuclear reactor determines if the outer channel may be thickened, reinforced, and/or fabricated of Zircaloy-4 or similar distortion-resistant material, so as to reduce or prevent distortion of the channel against the control blade, or thinned so as to increase water volume and enhance reactivity in the assembly. Reactor cores having configured fuel assemblies include fuel assemblies having different outer channels. Methods include determining operational characteristics of the fuel assembly, including likelihood of being placed directly adjacent to an employed control blade, and physically selecting or modifying the outer channel of the fuel assembly based thereon.

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.

The fuel assembly includes at least one fuel rod and an outer channel with four sidewalls surrounding the fuel rod, the outer channel having a configuration based on a position of the fuel assembly within a core of the nuclear reactor, wherein at least a first select sidewall, of the four sidewalls of the outer channel, is a reinforced sidewall, the remaining sidewalls of the outer channel, other than the at least a first select sidewall, are non-reinforced sidewalls, the at least a first select sidewall being in a controlled location that faces and is directly adjacent to a control blade that is to be utilized in the nuclear reactor, wherein an entirety of the reinforced sidewall as a whole is at least one of thicker and made from a material that is more resistant to radiation-induced deformation as compared to an entirety of the non-reinforced sidewalls.