1990’s - Nuclear Power Station
The most modern kind of nuclear power station to be built in Britain uses a pressurised water reactor to generate electricity. This is seen inside the heavily reinforced dome on the right; to the left is the turbine hall where power is generated. Nuclear power provides a means of insurance against the supply problems and fluctuating costs associated with fossil fuels. It may also help reduce the problem of global warming, caused in part by the emission of carbon dioxide from conventional power stations. If it is as 'clean' as is claimed, why has nuclear power aroused such controversy?
Britain's most modem nuclear power station, shown here, is the pressurised water reactor (PWR) at Sizewell in Suffolk. The cutaway shows the nuclear reactor vessel surrounded by four steam generators, together with the associated coolant pumps and a pressuriser unit. Inside the PWR, atoms of enriched uranium oxide absorb a neutron which causes them to split or 'fission' and produce heat. The fuel, in pellet form, is contained in tubes deep inside the reactor which are cooled by pressurised water. The operation of the reactor and the rate of energy release are regulated by the insertion and withdrawal of metal control rods which absorb neutrons from the core. Heat produced in the reactor is removed by the coolant water and transferred to the steam generators. The steam produced in this secondary circuit is used to drive turbogenerators which produce electricity, just as in a coal-fired power station. There are a number of different designs of nuclear reactor in Britain, including the advanced gas-cooled reactor (AGR) and Magnox. Here, instead of using water to moderate the neutrons produced in the fission process and thus encourage further fissions in a controlled chain reaction, blocks of graphite are used and the heat is carried to the boilers by carbon dioxide gas. With public confidence in the safety of nuclear power badly dented by the catastrophic accident at Chernobyl, doubts about the cost-effectiveness of nuclear power — once championed as the most economic form - have brought about a major review of official policy. No other energy source is so controversial.
|1930’s - Coal-fired Power Station|