Patent Number: 
Section: claims

1. A boiling water reactor nuclear power plant, in which a cooling water is circulated, comprising, in an installed state thereof: a reactor building;  a reactor containment vessel positioned in the reactor building; said reactor containment vessel having dual cylindrical structure having inner and outer wall sections;  a reactor pressure vessel disposed inside the containment vessel;  a dry well defined, inside the reactor containment vessel, by the inner wall section thereof;  a pressure suppression pool provided inside the reactor containment vessel and outside the dry well between the inner and outer wall sections of the reactor containment vessel;  a containment vessel cooling system pool disposed above the suppression pool;  a reactor core mounted with fuel assemblies supported by a reactor core support plate and an upper grid plate provided plate provided in an inner base portion of the reactor pressure vessel, said reactor core being disposed below said pressure suppression pool;  a reactor core shroud surrounding the reactor core and the upper grid plate; control rod guide tubes positioned in the reactor core shroud and over the upper grid plate;  control rods inserted in the control rod guide tubes; and  control rod drive mechanisms operative for inserting and withdrawing the control rods from an upper portion of the reactor core, said control rod drive mechanisms being arranged at a portion above the control rod guide tubes and inside the reactor core shroud,  said inner and outer wall sections of the reactor containment vessel having an inner hollow structure, the double-wall structure being communicated with the containment vessel cooling system pool, wherein said cooling water therein flows and circulates in the hollow portion of the double-wall structure to cool the dry well, the double-wall structure being provide with a plurality of ribs. 2. The boiling water reactor nuclear power plant according to  claim 1 , wherein said pressure suppression pool being connected to said nuclear reactor pressure vessel by means of gravity-based piping through which the cooling water drops by gravity. claim 1 3. The boiling water reactor nuclear power plant according to  claim 1 , wherein a piping and nozzles connected to said nuclear reactor pressure vessel are positioned above said reactor core. claim 1 4. The boiling water reactor nuclear power plant according to  claim 1 , wherein a valve operable to open to an exterior of said reactor core shroud is provided at a position above said fuel assembly. claim 1 5. The boiling water reactor nuclear power plant according to  claim 1 , wherein said pressure suppression pool and a lower portion of the dry well are connected by means of a plurality of emergency opening passages at different elevational positions. claim 1 6. The boiling water reactor nuclear power plant according to  claim 1 , wherein a normal use cooling system is connected to the inner hollow structure of the reactor containment vessel wall. claim 1 7. The boiling water reactor nuclear power plant according to  claim 1 , wherein a normally-closed water discharge pipe is led from said pressure suppression pool into said dry well at a base region of said nuclear reactor pressure vessel, and said water discharge pipe is normally closed by a sealing device capable of being released in case of emergency so as to open said water discharge pipe. claim 1 8. The boiling water reactor nuclear power plant according to  claim 1 , wherein a heat pipe capable of exchanging heat is provided at a portion between said pressure suppression pool and a lower region of said dry well. claim 1 9. The boiling water reactor nuclear power plant according to  claim 1 , wherein a guard pipe is provided so as to extend from said dry well section to said pressure suppression pool, and valves and piping led from said nuclear reactor pressure vessel are accommodated in said guard pipe. claim 1 10. The boiling water reactor nuclear power plant according to  claim 1 , wherein a turbine system is installed on an upper portion of the reactor building. claim 1 11. The boiling water reactor nuclear power plant according to  claim 1 , wherein an extraction space capable of accommodating said nuclear reactor pressure vessel is provided above the nuclear reactor pressure vessel in the reactor building. claim 1 12. The boiling water reactor nuclear power plant according to  claim 1 , wherein said reactor building is positioned on a foundation base having an anti-seismic structure. claim 1 13. A reactor containment vessel for use with a boiling water nuclear reactor having a reactor containment vessel cooling system providing cooling water, comprising: an inner wall made from multiple steel plates defining an inside of the reactor containment vessel;  an outer wall made from multiple steel plates, wherein the inner wall and the outer wall are positioned to form a double-wall structure forming an inner hollow structure over at least a portion of the reactor containment vessel;  a plurality of ribs provided within the inner hollow structure and coupled to either or both of the inner wall and the outer wall and;  a fluidic connection to the reactor containment vessel cooling system configured so that cooling water from the reactor containment vessel cooling system flows and circulates in the inner hollow structure to cool a portion of the inside of the reactor containment vessel.