Abstract: Provided is a structure including a first member (2); a second member (3) disposed opposite to the first member (2); and a glass layer (4) disposed between the first member (2) and the second member (3) so as to bond the first member (2) and the second member (3). A glass transition point of the glass layer (4) is lower than a temperature of the glass layer (4) under operation. In the glass layer (4), at least either of ceramic and metallic particles 4b, 4c is dispersed. In a temperature region lower than the glass transition point of the glass layer (4), a thermal expansion coefficient thereof falls in between thermal expansion coefficients of the first member (2) and the second member (3). This allows thermal strain caused within the structure (1) to be reduced when the structure (1) is operated at a higher temperature than a room temperature.

Abstract: Provided is a structure including a first member (2); a second member (3) disposed opposite to the first member (2); and a glass layer (4) disposed between the first member (2) and the second member (3) so as to bond the first member (2) and the second member (3). A glass transition point of the glass layer (4) is lower than a temperature of the glass layer (4) under operation. In the glass layer (4), at least either of ceramic and metallic particles 4b, 4c is dispersed. In a temperature region lower than the glass transition point of the glass layer (4), a thermal expansion coefficient thereof falls in between thermal expansion coefficients of the first member (2) and the second member (3). This allows thermal strain caused within the structure (1) to be reduced when the structure (1) is operated at a higher temperature than a room temperature.

Abstract: A fuel assembly, comprising: a plurality of first fuel rods including uranium and not including a burnable poison; a plurality of second fuel rods including said uranium and said burnable poison; and a water rod; wherein said second fuel rods are placed at corners of an outermost layer of a fuel rod array; other second fuel rods are placed, in said outermost layer, adjacent to said second fuel rods placed at said corners; and other second fuel rods are placed adjacent to said water rod.

Abstract: A fuel assembly has a constitution in which plural fuel rods are arranged in 10 rows by 10 columns in a channel box, and includes plural fuel rods G containing gadolinium and plural partial length fuel rods P. In the fuel assembly, average enrichment of lower portion cross section is approximately 4.6 wt %, and average enrichment of upper portion cross section is approximately 4.7 wt %. The average enrichments at the outermost layer are approximately 5.6 wt % both in the upper portion and the lower portion. Ratios e/x of the average enrichment of the outermost layer e (wt %) to the average enrichment of the fuel assembly cross section x (wt %) are 1.19 in the upper portion and 1.22 in the lower portion, and the ratios satisfy equation (1). [ Equation ? ? 1 ] ? e x ? - 18.3 ? ( x 10 ) 5 + 68.766 ? ( x 10 ) 4 - 101.77 ? ( x 10 ) 3 + 74.428 ? ( x 10 ) 2 - 27.372 ? ( x 10 ) + 5.

Abstract: A fuel assembly, comprising: a plurality of first fuel rods including uranium and not including a burnable poison; a plurality of second fuel rods including said uranium and said burnable poison; and a water rod; wherein said second fuel rods are placed at corners of an outermost layer of a fuel rod array; other second fuel rods are placed, in said outermost layer, adjacent to said second fuel rods placed at said corners; and other second fuel rods are placed adjacent to said water rod.

Abstract: An method for operating a nuclear power generation plant, comprising the steps of: forming a plurality of control rod patterns by operating a plurality of control rods during a first period of one operation cycle of a reactor including said first period before a point of time when all control rods are completely withdrawn from a core of said reactor and a core flow rate reaches firstly a set core flow rate, and a second period after said point of time, controlling stepwise at least once a temperature of feed water supplied to said reactor based on a different set feed water temperature during a period included in said first period for operating said reactor with a formed same control rod pattern, and continuing feed water temperature control based on said set feed water temperature until said core flow rate reaches a set core flow rate set based on said set feed water temperature.

Abstract: The present invention decreases the temperature of feed water supplied to the reactor of a set power when the flow rate of coolant supplied to the core of the reactor increases in the end of an operation cycle. This operating method can increase the thermal power of the nuclear power generation plant and increase the economical efficiency of fuel even when the operation cycle is prolonged. Particularly, even when the core flow rate increases in the end of the operation cycle, this method can suppress the rise of the cooling water temperature at the inlet of the core. Consequently, this invention can make the reactivity gain higher than that when the core flow rate is singly increased. The present invention can increase the thermal power of a nuclear reactor, and can improve the economical efficiency of fuel even when a period of an operation cycle is made longer.

Abstract: The natural circulation type boiling water reactor comprises a core in which a plurality of fuel assemblies are loaded, and a chimney which is disposed above the core and has a path partition which forms a plurality of vertical lattice paths. A uniform pressure space is formed between the core and the chimney and not disposed the path partition. The two-phase flow including the cooling water and the steam exhausted from the core through the uniform pressure space is supplied to the vertical lattice paths. The two-phase flow ascends in the vertical lattice paths. Thus, the flow distribution for each fuel assembly can be calculated using the pressure difference between the upper end and the lower end of the core can be calculated without the need for the void fraction of the lattice paths.

Abstract: A core disposed in a reactor pressure vessel includes one layer (an outermost region) at an outermost side of the core, two-three layers (an outer region) inside the outermost region and other layers (an inner region) inside the outer region. Fuel assemblies arranged in the core are supported by fuel supports having orifice. Orifice pressure loss coefficient of the orifice in the outermost region is set to be maximum and the orifice pressure loss coefficient of the orifice in the outer region is set to be minimum such that the flow rate of the coolant W for each fuel assembly in the outermost region is lowest and that for each fuel assembly in the outer region is highest. In the core of the natural circulation boiling water reactor, the reactor power distribution in a radial direction is flattened, and it is possible to increase the thermal margin.