All heat engines lose coolant, no seal is perfect. Even if your primary coolant loop is perfect, you still have to evaporate a heck of a lot of water in the sec

All heat engines lose coolant, no seal is perfect. Even if your primary coolant loop is perfect, you still have to evaporate a heck of a lot of water in the secondary loop just to get rid of the heat. This pdf[1] quotes 600-800 US gallons per MWh. Even shut down the core is producing megawatts of heat. If an operating helium-cooled reactor loses all its coolant, you're going to have a bad day, but the same thing can be said about a water-cooled reactor. 1: http://www.ucsusa.org/sites/default/files/legacy/assets/documents/nuclear_power/fact-sheet-water-use.pdf http://www.ucsusa.org/sites/default/files/legacy/assets/docu...