Passive nuclear reactor cooling system using compressed gas energy and coolant storage outside nuclear plant

#A nuclear power plant generates electricity by using a nuclear reactor to boil feed water to create high-pressure steam. This steam in turn drives turbines, which in turn drive electrical generators that create the electricity. The feed water is called the “primary coolant” in the nuclear industry since it absorbs and carries away the heat generated by the nuclear fuel rods in a reactor pressure vessel (RPV) inside the reactor. After the steam drives the turbines it is condensed back to water and is recirculated back to the RPV to be heated again to continuously generate new steam for the turbines.

#Sometimes it is necessary to shut down a nuclear plant for operational reasons or because of an accident or terrorist attack, loss of outside electrical power, or a natural event such as an earthquake or fire. Thus some means must be provided to stop the nuclear chain reaction which is continuously occurring in the reactor. This is done by inserting control rods and-or chemical substances into the reactor to absorb the fission neutrons that drive the nuclear chain reaction and heat the primary coolant. However, stopping the nuclear reaction does not eliminate the danger or cool the reactor adequately. A major source of heat, called the “decay heat,” remains. This decay heat is generated by radioactive decay of isotopes within the nuclear fuel rods. Even after shutdown this heat must be continually removed from the nuclear fuel rods for days or weeks in order to stabilize the reactor. Otherwise, a nuclear “meltdown” can occur, as happened in the Three Mile Island, Pa. (1979) and Fukushima Daiichi, Japan (2011) nuclear accidents.

#During normal power generation, the primary coolant circulates through plumbing (termed the “primary boundary”) coupled to the RPV. The primary boundary includes an outlet pipe from the RPV (commonly called the “hot leg”) that carries the steam generated from the primary coolant to the turbines. After condensation back to water the primary coolant is returned to the RPV by a pipe called the “cold leg.”

#FIG. 1 shows a schematic diagram of one aspect of a CGES system.

#FIG. 2 is a cross-sectional view of one aspect of a CGES system.

#FIG. 3 is a schematic diagram of a nuclear power plant showing fluid flow after a SCRAM.

#REFERENCE NUMERALS 100 Nuclear power plant 102 Reactor pressure vessel (RPV) 104 Primary containment vessel 106 Tank (PCV) 108 Water 110 Pressure 112 Tank 114 Pressure 116 Heat exchanger 118 Ground level 120 Pipe 122 Valve 124 Pipe 126 Valve 128 Expansion valve 130 Coil 132 Volume 134 Pipe 136 Pipe 138 Pipe 140 Pipe 142 Valve 144 Spent-fuel pool 146 Pipe 148 Valve 200 Casing 205 Grout 210 Plug 215 Lid 220 Gasket 225 Blocks 230 Bolts 235 Brackets 240 Welds 245 Pipe 255 Valve 260 Handle 265 Pipe 270 Valve 290 Pipe 295 Pipe 300 Manifold 305 Valve 310 Valve 315 Pipe 320 Pipe 325 Valve 330 Valve 335 Valve 350 Manifold 400 CGES units 405 Pipes 410 Valves 415 Tanks 420 Tank 425 Valve 500 Railroad tank car 505 Track 510 Tanks 515 Manifold 520 Pipes 600 Railroad flat car 700 Housing 705 Trench 710 Fence 715 Roof 720 Tracks 800 CAeS system 805 Cavern 810 Heat exchanger 812 Coils 814 Pipe 815 Turbine 820 Generator 822 Conductors 825 Compressor 830 Pipe 835 Valve 840 Turbine 845 Generator 850 Conductors 855 Conductors 870 Valve 875 Pipe 881 Pipe 900 Fuel rods 905 Baffle 910 Manifold 915 Openings 920 Pool 925 Pipe 930 Valve 935 Pipe 940 Valve 945 Pipe 950 Valve 1100 Plate 1105 Plate

#CG Compressed Gas CAeS Compressed Air Energy System CGES Compressed Gas over Water Emergency Reactor Cooling System DPCS Prior-Art Depressurization and Cooling System GJ GigaJoules MW MegaWatts MJ MegaJoules NCAP A combined Nuclear and CAeS Power plant design PCV Primary Containment Vessel RPV Reactor Pressure Vessel RRTC Railroad Tank Car SCRAM Safety Control Rod Axe Man—an emergency shutdown of an operating nuclear power plant. SFP Spent Fuel Pool Overview

#In one embodiment, CG is safely stored at high pressure in one tank and is used to pressurize cooling water in another, larger tank. The CG is admitted to pressurize the cooling water when it is needed during a nuclear emergency. In one aspect the heat required for rapid expansion of large volumes of the CG is extracted from the water that is pressurized by the expanding gas. Equal volumes of water and expanded gas pass through a heat exchanger so that there is always sufficient heat energy for the gas to expand. The temperature drop in the water due to contact with the expanding gas is small. In another aspect, very large quantities of CG from a CAeS plant are used to cool a companion nuclear reactor by expansion of the compressed gas alone inside the reactor during emergencies. This aspect provides great cost savings to the CAeS during normal power generation that pays for the CAeS installation near a companion nuclear power station. A CAeS is a relatively inexpensive power plant (3% or less of the cost of a nuclear plant) that can be installed outside existing or new nuclear power stations.