ABSTRACT
Nature is niggardly in its provision of uranium isotopes capable of use in today's reactors. A nuclear reactor is a means of controlling the chain reaction and converting the energy produced into heat and subsequently into electricity. The world's major concentrations of nuclear power stations are dominated by reactors using water as coolant and moderator. There are two types of water reactor. The pressurized water reactor (PWR) is one in which water at high pressure is heated within the reactor core and passes to heat exchangers where it boils water in a secondary circuit. The boiling water reactor (BWR) is one in which the water in the core is allowed to boil and the steam from the coolant drives the turbines directly. Both types use enriched uranium dioxide fuel clad with zirconium alloy. PWRs were first developed by the USA and the USSR as a compact reactor for marine propulsion, especially in submarines.
