Abstract: In view of above problems, an object of the invention is to provide a primary containment vessel venting system having a structure capable of continuously discharging vapor in a primary containment vessel out of the system and continuously reducing pressure of the primary containment vessel without discharging radioactive noble gases to the outside of the containment vessel and without using an enclosing vessel or a power source. In order to achieve the above object, an nuclear power plant of the invention includes a primary containment vessel which includes a reactor pressure vessel, a radioactive substance separation apparatus which is disposed inside the primary containment vessel and through which the radioactive noble gases do not permeate but vapor permeates, a vent pipe which is connected to the radioactive substance separation apparatus, and an exhaust tower which is connected to the vent pipe and discharges a gas, from which a radioactive substance is removed, to the outside.

Abstract: In view of above problems, an object of the invention is to provide a primary containment vessel venting system having a structure capable of continuously discharging vapor in a primary containment vessel out of the system and continuously reducing pressure of the primary containment vessel without discharging radioactive noble gases to the outside of the containment vessel and without using an enclosing vessel or a power source. In order to achieve the above object, an nuclear power plant of the invention includes a primary containment vessel which includes a reactor pressure vessel, a radioactive substance separation apparatus which is disposed inside the primary containment vessel and through which the radioactive noble gases do not permeate but vapor permeates, a vent pipe which is connected to the radioactive substance separation apparatus, and an exhaust tower which is connected to the vent pipe and discharges a gas, from which a radioactive substance is removed, to the outside.

Abstract: An atomic power plant is provided including a primary containment vessel (PCV) 1, a reactor pressure vessel (RPV) 3, a main steam line 4, two steam safety relief valves (SRVs) 6, a pressure suppression pool (S/P) 8, an SRV exhaust pipe 9 which is connected to a quencher 10, a temperature measuring instrument 12 which measures a temperature inside the quencher 10, an SRV controller 13 which controls opening and closing of the SRVs 6. After a lapse of predetermined time from when the SRV 6 is opened, in a case where it is determined that a temperature detected by the temperature measuring instrument 12 is equal to or smaller than a predetermined threshold value, the SRV controller 13 causes the SRV 6 to which the temperature measuring instrument 12 detecting the temperature leads, to be closed and to be prohibited from being opened.

Abstract: [Problem] Provided is an atomic power plant which can be applied to reactors including existing reactors through a simple method and in which a pressure in a primary containment vessel can be restrained from excessively rising in a case where a steam leakage from an exhaust pipe of a stream safety relief valve occurs. [Solution] There are provided a PCV 1, an RPV 3, a main stream line 4, two SRVs 6, an S/P 8, an SRV exhaust pipe 9 which is connected to a quencher 10, a temperature measuring instrument 12 which measures a temperature inside the quencher 10, an SRV controller 13 which controls opening and closing of the SRVs 6.

Abstract: The invention includes a heat exchanger provided at a position higher than a primary containment vessel; a condensate storage tank disposed below the heat exchanger and above an upper end of a reactor core placed in a reactor pressure vessel; a non-condensate gas discharge line connected to an upper section of the condensate storage tank and to a suppression pool; a second condensate discharge line connected to a position below that section of the condensate storage tank to which a first end of the non-condensate gas discharge line is connected, and to the suppression pool; and a condensate return line connected to a position below that section of the condensate storage tank to which a first end of the second condensate discharge line is connected, and to a side portion of the reactor pressure vessel, the side portion being above the upper end of the core.

Abstract: The invention includes a heat exchanger provided at a position higher than a primary containment vessel; a condensate storage tank disposed below the heat exchanger and above an upper end of a reactor core placed in a reactor pressure vessel; a non-condensate gas discharge line connected to an upper section of the condensate storage tank and to a suppression pool; a second condensate discharge line connected to a position below that section of the condensate storage tank to which a first end of the non-condensate gas discharge line is connected, and to the suppression pool; and a condensate return line connected to a position below that section of the condensate storage tank to which a first end of the second condensate discharge line is connected, and to a side portion of the reactor pressure vessel, the side portion being above the upper end of the core.

Abstract: In a fuel assembly having fuel rods U1 to U4, and P1 not containing gadolinia, and fuel rods G1-G3 containing gadolinia, the concentrations a of gadolinia in nuclear fuel materials A (8 wt % and 10 wt %) satisfy 0.7<a/amax?1.0, the concentrations b of gadolinia in nuclear fuel materials B (5 wt % and 6 wt %) satisfy 0.4<b/amax?0.7, the concentration c of gadolinia in a nuclear fuel material C (2 wt %) satisfies 0<c/amax?0.4, and L(A)/5.0?L(B) and L(B)/5.0?L(C) are satisfied. The gadolinia with concentrations a burns out during the end of cycle, the gadolinia with concentrations b during the middle of cycle, and the gadolinia with a concentration c during the beginning of cycle. L(A) is the total axial length of zones filled with the nuclear fuel materials A in the fuel rods G1-G3, L(B) for materials B in G2 and G3, and L(C) material C in G1.

Abstract: A ratio of the number of fuel assemblies loaded on a core to the number of control rod drive mechanisms is 3 or more. The fuel assembly itself contains mixed oxides of a low enrichment concentration uranium oxide containing 3 to 8 wt % in the average enrichment concentration of the fuel assembly, or mixed oxide containing not less than 2 wt %, but less than 6 wt % in the average enrichment concentration of fissile plutonium of. In the burner type BWR core on which the fuel assemblies are loaded, an average weight density of uranium, plutonium and minor actinides is 2.1 to 3.4 kg/L as a conversion at the value of unburned state.

Abstract: A ratio of the number of fuel assemblies loaded on a core to the number of control rod drive mechanisms is 3 or more. The fuel assembly itself contains mixed oxides of a low enrichment concentration uranium oxide containing 3 to 8 wt % in the average enrichment concentration of the fuel assembly, or mixed oxide containing not less than 2 wt %, but less than 6 wt % in the average enrichment concentration of fissile plutonium of. In the burner type BWR core on which the fuel assemblies are loaded, an average weight density of uranium, plutonium and minor actinides is 2.1 to 3.4 kg/L as a conversion at the value of unburned state.

Abstract: In order to stably control a nuclear reactor in a short time, so as not to enter an unstable region that is determined by the relationship between the reactor pressure, the reactor power and the subcooling of the core inlet coolant at start-up time, the nuclear reactor system comprises: an power control apparatus for generating a control rod operation signal for operating a control rod, based on the reactor water temperature change rate; a feed water control apparatus for generating a feed water flow rate signal and a discharge water flow rate signals based on the reactor water level signal; and a process computer for performing overall control of the power control apparatus and the feed water control apparatus, wherein the feed water control apparatus has the reactor water temperature change rate setting section for adjusting the reactor water temperature change rate set value based on the variation of the reactor water level signal.

Abstract: In order to stably control a nuclear reactor in a short time, so as not to enter an unstable region that is determined by the relationship between the reactor pressure, the reactor power and the subcooling of the core inlet coolant at start-up time, the nuclear reactor system comprises: an power control apparatus for generating a control rod operation signal for operating a control rod, based on the reactor water temperature change rate; a feed water control apparatus for generating a feed water flow rate signal and a discharge water flow rate signals based on the reactor water level signal; and a process computer for performing overall control of the power control apparatus and the feed water control apparatus, wherein the feed water control apparatus has the reactor water temperature change rate setting section for adjusting the reactor water temperature change rate set value based on the variation of the reactor water level signal.

Abstract: A natural circulation boiling water reactor includes a reactor pressure vessel, a chimney including a lattice member and arranged above a core in said reactor pressure vessel, and a plurality of thermocouple extension wire pulling conduits into which at least one temperature detection thermocouple and at least one cable connected to the temperature detection thermocouple are inserted. At least one of thermocouple extension wire pulling conduits is disposed on an upper end surface of the lattice member and is directly mounted to the upper end surface of the lattice member.

Abstract: A natural circulation boiling water reactor includes a reactor pressure vessel, a chimney including a lattice member and arranged above a core in the reactor pressure vessel, and at least one thermocouple extension wire pulling conduit into which a temperature detection thermocouple and a cable connected to said temperature detection thermocouple are inserted. The thermocouple extension wire pulling conduit is disposed on an upper end surface of the lattice member and mounted to the upper end surface of the lattice member.

Abstract: A ratio of the number of fuel assemblies loaded on a core to the number of control rod drive mechanisms is 3 or more. The fuel assembly itself contains mixed oxides of a low enrichment concentration uranium oxide containing 3 to 8 wt % in the average enrichment concentration of the fuel assembly, or mixed oxide containing not less than 2 wt %, but less than 6 wt % in the average enrichment concentration of fissile plutonium of. In the burner type BWR core on which the fuel assemblies are loaded, an average weight density of uranium, plutonium and minor actinides is 2.1 to 3.4 kg/L as a conversion at the value of unburned state.

Abstract: A chimney lattice is arranged in a reactor pressure vessel. Thermocouple extension wire pulling conduits inserting a temperature detection thermocouple and a cable connected to the thermocouple are mounted to the upper end of the chimney lattice. By mounting the thermocouple extension wire pulling conduit on the upper end of the chimney lattice, the thermocouple extension wire pulling conduit does not become an obstacle when the fuel assembly is taken out from the chimney. Because the thermocouple extension wire pulling conduit is installed at the upper end of the chimney, the replacement of the thermocouple damaged is easy.

Abstract: A ratio of the number of fuel assemblies loaded on a core to the number of control rod drive mechanisms is 3 or more. The fuel assembly itself contains mixed oxides of a low enrichment concentration uranium oxide containing 3 to 8 wt % in the average enrichment concentration of the fuel assembly, or mixed oxide containing not less than 2 wt %, but less than 6 wt % in the average enrichment concentration of fissile plutonium of. In the burner type BWR core on which the fuel assemblies are loaded, an average weight density of uranium, plutonium and minor actinides is 2.1 to 3.4 kg/L as a conversion at the value of unburned state.