Nuclear Reactors Don’t Need to Be So… | The Breakthrough Institute

Nuclear Reactors Don’t Need to Be So… | The Breakthrough Institute: The Breakthrough Institute is an environmental research center based in Berkeley, California. Our research focuses on identifying and promoting… Thirsty Electricity By Matthew L Wald Shifting rainfall patterns may require changes to electricity generation A central selling point for solar and wind power installations is that they use very little water. But what about nuclear? Can nuclear be similarly thrifty with this limited resource? The subject needs to be clarified. Today’s nuclear plants use water in two different roles. And the first tranche of new, small modular reactors will likely do the same. Fuel in the reactor vessel is immersed in water. That water “moderates” the flow of neutrons, the sub-atomic particles released in fission. It slows the neutrons down to a speed more likely to cause another fission. The water also carries off the heat generated by fission, so it can be turned to steam and put to work to spin a turbine, creating mechanical energy that turns a generator and makes electricity. One problem for steam-electric plants (including coal plants) is that when this steam exits the turbine, depleted of much of its energy, it needs to be re-heated to gain the energy needed to spin the turbine again. But it’s hard to heat steam, so the engineers have to find a way to condense it back into water. Cooling the steam and turning it back into liquid water requires more cooling water. In some future reactors, water requirements will be smaller. Gas-graphite reactors, for example, heat an inert gas, use the hot gas to spin the turbine, and then route the gas back to the core for re-heating. But the material is a gas in the entire process; it does not have to be condensed back to a liquid for re-heating. To understand how reactors in service today use water and how that compares to plants that burn fossil fuels for energy, it is worth looking into each type in more detail.