• The cold water moves in sealed pipes through the heat exchanger and is converted to steam by the coolant energy.
• The steam is sent at high pressure through the turbines to generate electricity. • The shielding prevents radiation leaks.
Note how the main chain reaction occurs between fuel rods. Without the moderator, the neutrons would be too fast to cause sustainable fission (Fig. 31.27).
fission moderator moderator fission U-235 U-235 moderator
control rods
slow
neutron
control rods
FIG. 31.27 The moderator slows down the fast neutrons to allow sustainable fission Advantages of nuclear fission power
• Nuclear power emits no harmful greenhouse gases. • It produces massive amounts of energy very economically. • There will be no shortage of nuclear fuel (unlike non-renewable fossil fuels). • Nuclear energy reduces the need for fossil fuels. • Reactors can be used to create new elements for research and development. • Nuclear power has a very low accident rate compared to other energy sources.
Disadvantages of nuclear fission power
• Radioactive waste has a very long half-life and is expensive to store. • Reprocessing of fuel is hazardous and expensive. • If a major accident occurs, such as at Chernobyl in 1986, there can be a large-scale health hazard. (It should be noted that Chernobyl was actually a steam explosion but it happened in the core.) The 2011 tsunami in Japan caused serious problems at the Fukushima nuclear power plant. The Japanese government plans to phase out nuclear power by the 2030s.
