Patent Number: 
Section: claims

1. An injection system for a neutron poison for an emergency shutdown of a nuclear reactor, the injection system comprising:an absorber liquid having an absorption cross section that captures free neutrons;a pressure vessel containing a propelling fluid being essentially water;an overflow line communicating with a core region of a reactor pressure vessel of a nuclear reactor, the core region being external to said pressure vessel;a reservoir vessel storing said absorber liquid at room temperature, said reservoir vessel connected, via said overflow line, to said pressure vessel; andan outflow line connected to said bottom region of said reservoir vessel; anda shut-off apparatus having a closed position that closes said outflow line and an open position that opens said outflow line thereby causing the absorber liquid to be pushed through said outflow line by the propelling fluid;said reservoir vessel being spatially separated from said pressure vessel, and only said overflow line connecting said reservoir vessel to said pressure vessel such that pressure is equalized between said reservoir vessel and said pressure vessel;said pressure vessel formed with a ceiling region and a bottom region, said pressure vessel including a heating device configured to heat and partially evaporate the propelling fluid in order to form a vapor cushion located in said ceiling region of said pressure vessel, wherein an un-evaporated portion of the propelling fluid defines a liquid portion located below the vapor cushion;said overflow line connecting said bottom region of said pressure vessel to said ceiling region of said reservoir vessel, said overflow line including a riser; andsaid overflow line including a plurality of nozzles discharging the propelling fluid near said ceiling region of said reservoir vessel. 2. The injection system according to claim 1, wherein said bottom region of said pressure vessel has an outflow opening formed therein for removal of said absorber liquid. 3. The injection system according to claim 1, wherein said pressure vessel, said reservoir vessel and said overflow line are pressure-loaded components constructed to operate at a pressure of more than 100 bar. 4. The injection system according to claim 1, wherein said pressure vessel and said heater cooperate such that said propelling fluid is always available at a temperature of more than 300° C. 5. The injection system according to claim 1, wherein said reservoir vessel is dimensioned to hold a quantity of said absorber liquid which is sufficient for shutting down the nuclear reactor. 6. The injection system according to claim 1, wherein said pressure vessel is dimensioned to hold a quantity of said propelling fluid which is sufficient to completely displace said absorber liquid from said reservoir vessel. 7. The injection system according to claim 1, wherein said absorber liquid is an aqueous boron solution stored in said reservoir vessel. 8. The injection system according to claim 1, wherein said pressure vessel, said reservoir vessel and said overflow line are pressure-loaded components constructed to operate at a pressure of approximately 150 bar. 9. The injection system according to claim 1, wherein said pressure vessel and said heater cooperate such that said propelling fluid is always available at a temperature of approximately 340° C. 10. The injection system according to claim 1, wherein said plurality of nozzles discharge the propelling fluid such that the propelling fluid is prevented from mixing with the absorber liquid after the propelling fluid exits said plurality of nozzles.