How Nuclear Power Works
A nuclear reactor is designed to produce heat, which is used to produce heat, which is used to produce steam, which then drives an electricity generator. In a nuclear power station the reactor plays the part of the coal or oil -fired boiler in a conventional power station. Note - nuclear power can only produce electricity; it can't replace petrol in vehicles.
The nuclear industry is possible because of radioactive elements - substances that give off radiation because they're unstable and - in minutes or millions of years - break
down into other elements. The radiation given off consists of very small particles of matter travelling very fast (known as alpha or beta particles) and energy (known as gamma rays ). The waves of energy given of harmless energy - such as light and radio waves - and other energy that's harmful in some way - such as x-rays and microwaves. It's just the wavelength that differs. Radiation from radioactive elements is particularly dangerous because it travels right into our bodies and damages the centres of our cells, killing or mutating them. More over, we can eat, or breathe in radioactive substances - and some of them are actually used by our bodies, which can't distinguish between radioactive elements and their normal counterparts, for for example between radioactive iodine and stable, non-radioactive iodine.
Certain radioactive elements, such as uranium, can be made to split by hitting the centre of the atom with a neutron which is a smaller atomic particle. When it splits (undergoes fission) it releases a vast amount of heat - some of the matter in the atom ยท actually t urned into energy - and, what is more, it gives off several more neutrons. If these in tum hit other uranium atoms, they cause them to split, releasing yet more neutrons to hit more atoms ... and so on. In an atomic bomb things are arranged so that the process goes out of control and leads to an explosion, whereas in nuclear power stations this is (usually!) controlled.
The heat produced by the fission is taken away from the reactor core - where the uranium is - by a continuous flow of gas or liquid coolant. (Advanced Gas-Cooled Reactors use gas. as a coolant, Pressurised Water Reactors use water.) The coolant flow must not be interrupted or heat builds up in seconds and the reactor core can melt or catch fire. The worst possible accident in a conventional nuclear power station is a core meltdown, when the reactor core melts and sinks into the earth. The "experts" don't know what would happen then. Would it spray radioactive liquid over thousands of square miles, or would it bore a hole through the earth? In America it is called the China Syndrome because the core could theoretically bum its way to China - from here it would head for New Zealand. Well they almost had a chance to find out - it nearly happened last spring at Three Mile Island.
However, that's not the only thing to worry about. During the fission of uranium in a reactor, large amounts of other radioactive elements are formed some of them more
dangerous than uranium. Plutonium, named after Pluto, the god of hell, is one of them. It's a man-made poisonous metal produced only in nuclear reactors. It gets into the lungs, concentrates in the ovaries (and testes) and in minute quantities causes cancer. The current "acceptable" dose is set at less than one millionth of a gram, though there is evidence that this is too high. Cancer may not appear until 15-30 years after a very slight exposure (remember that you will die immediately if you get a large enough dose of radiation); then, if the corpse is cremated, the plutonium goes up the flue into the air to be breathed into someone else's lungs ... Plutonium takes a quarter of a million years to decay to half. 15 lbs of plutonium is enough to make one atom bomb. In Britain alone, our 11 commercial nuclear power stations produce roughly 20001bs of plutonium a year.
In order to obtain as much use of the fuel as possible, when the fuel in the reactor becomes too contaminated with radioactive by-products, it is taken to a fuel reprocessing plant, where they are separated from the uranium and plutonium. Uranium is re-formed into fuel rods and returned to the reactor. In Britain this plant is at Wind scale, Cumbria.
As uranium supplies are running low, the new experimental plutonium-fuelled fast breeder reactor is being hailed as the future hope of the nuclear industry. It's called the fast breeder because after ten to 20 years of reactor use, more plutonium is made than is used up. However, they are bedevilled with safety problems, are more expensive and much more potentially dangerous than other types of reactor (and that's saying something). Unlike uranium reactors, fast breeders can explode as nuclear bombs. The first experimental fast breeder reactor nearly eliminated Detroit in 1966.