CLIL CLIL CLIL LANGUAGE IMMERSION ENERGY NUCLEAR FISSION Nuclear power stations use the heat released by nuclear reactions to boil water to make steam. The type of nuclear reaction used is called nuclear fission. In nuclear fission: a neutron collides with a uranium nucleus, a uranium nucleus is large and unstable, Movable control rod Concrete shield the uranium nucleus splits into two similarsized smaller nuclei, Hot coolant out more neutrons are released, these neutrons can then collide with more uranium nuclei. Nuclear fuel Hot coolant out Graphite core These processes are repeated continuously, forming a chain reaction. Reactor The nuclear fuel, usually uranium oxide, is vessel held in metal containers called fuel rods. These are lowered into the reactor core. A Cold Cold coolant, usually water or carbon dioxide, is coolant coolant in circulated through the reactor core to remove in the heat. Control rods are also lowered into the core. These absorb neutrons and control the rate of the chain reaction. They are Outline of a nuclear reactor raised to speed it up, or lowered to slow it down. The energy released in nuclear fission is far greater than the energy released in a chemical reaction, such as burning fuel. This means that the power output of a nuclear power station is large. The lifetime of a nuclear power station is about 20 years. Advantages and disadvantages In considering nuclear power, it is important to weigh up the advantages and the disadvantages. Advantages: no carbon dioxide is produced when the station is operating there is a high power output a small amount of fuel is needed, compared with coal or gas. Disadvantages: hazardous radioactive waste is produced building power stations is quite expensive decommissioning power stations at the end of their lifetime is very costly. 40