Patent Number: 
Section: claims

1. An emergency core cooling system for a BWR plant not including external recirculation piping, comprising:an active emergency core cooling system consisting of only a first safety division and a second safety division, each of said first and second divisions including a high-pressure motor-driven core cooling system, and a low-pressure motor-driven core cooling system, which is commonly used as a residual heat removal system, a heat removal capacity of said residual heat removal system being not less than 100% of the necessary capacity to cool the core and the containment to meet a safety requirement at a design basis loss of coolant accident;a first emergency power supply equipment provided for the first safety division, the first emergency power supply equipment configured to supply electricity to the first safety division; anda second emergency power supply equipment provided for the second safety division, the second emergency power supply equipment configured to supply electricity to the second safety divisions;wherein said emergency core cooling system does not include additional safety divisions that contain an active emergency core cooling system, andwherein said emergency core cooling system meets the safety requirement at a design basis loss of coolant accident considering a single failure of any active components including said first or second emergency power supply equipment. 2. The emergency core cooling system according to claim 1, wherein the first power supply equipment is a first emergency diesel generator, and wherein the second power supply equipment is a second emergency diesel generator. 3. The emergency core cooling system according to claim 1, wherein the first power supply equipment is an emergency diesel generator, and wherein the second power supply equipment is an emergency gas turbine generator. 4. The emergency core cooling system according to claim 1, wherein the first power supply equipment is a first emergency gas turbine generator, and wherein the second power supply equipment is a second emergency gas turbine generator. 5. The emergency core cooling system according to claim 1, further comprising a passive cooling system comprising a, third safety division configured to physically separate said passive safety system from the active emergency core cooling system in the first and second safety divisions, said passive safety system including at least an isolation condenser to condense reactor steam and return condensate to the reactor in a high-pressure condition at a station blackout, wherein said active emergency core cooling system is configured to cool the core with said passive cooling system not operating. 6. A BWR plant comprising an emergency core cooling system comprising:an active emergency core cooling system consisting of only a first safety division and a second safety division, each of said first and second divisions including a high-pressure motor-driven core cooling system, and a low-pressure motor-driven core cooling system, which is commonly used as a residual heat removal system, a heat removal capacity of said residual heat removal system being not less than 100% of the necessary capacity to cool the core and the containment to meet a safety requirement at a design basis loss of coolant accident;a first emergency power supply equipment provided for the first safety division, the first emergency power supply equipment configured to supply electricity to the first safety division; anda second emergency power supply equipment provided for the second safety division, the second emergency pourer supply equipment configured to supply electricity to the second safety division;wherein said emergency core cooling system does not include additional safety divisions that contain an active emergency core cooling system, and said BWR plant does not include an external recirculation piping, andwherein said emergency core cooling system meets the safety requirement at a design basis loss of coolant accident considering a single failure of any active components including said first or second emergency power supply equipment. 7. The BWR plant according to claim 6, wherein the first power supply equipment is a first emergency diesel generator, and wherein the second power supply equipment is a second emergency diesel generator. 8. The BWR plant according to claim 6, wherein the first power supply equipment is an emergency diesel generator, and wherein the second power supply equipment is an emergency gas turbine generator. 9. The BWR plant according to claim 6, wherein the first power supply equipment is a first emergency gas turbine generator, and wherein the second power supply equipment is a second emergency gas turbine generator. 10. The BWR plant according to claim 6, further comprising a passive cooling system comprising a third safety division configured to physically separate said passive safety system form the active emergency core cooling system in the first and second safety divisions, said passive safety system including at least an isolation condenser to condense reactor steam and return condensate to the reactor in a high-pressure condition at a station blackout, wherein said active emergency core cooling system is configured to cool the core with said passive cooling system not operating.