On March 11, the strongest ever instrumentally recorded earthquake in Japan struck its northern coast. Ground shaking triggered the safety shut-down of 11 nuclear reactors and cut external power supplies to the Fukushima Daiichi nuclear plant complex. Located on the coast just southeast of the earthquake’s epicentre, the Fukushima plant withstood the ground motion but its back-up power supplies from diesel generators, needed to keep its reactor coolant pumps working, were disabled by the impact of a following 14-metre tsunami wave. Further back-up power from batteries kept the coolant pumps working for another eight hours. After this, the plant’s operators began emergency procedures designed to control the temperature of the reactor core, including the use of seawater to douse the structure. Resultant gases such as steam and hydrogen were vented, the hydrogen exploding on contact with oxygen in the atmosphere. As cooling efforts continued, officials from the plant’s owner, Tokyo Electric Power Company (Tepco) asserted that the situation was “improving.”
Media response to the Fukushima situation was apocalyptic. The 25th anniversary, on 26 April, of the 1986 Chernobyl nuclear plant explosion loomed. German commentators warned that Germany can no longer pretend that nuclear power is safe . Four days after the earthquake, Chancellor Angela Merkel ordered the shut-down of seven nuclear reactors which had been built before 1980. The European Commission agreed to introduce as yet undefined “stress tests” in Europe’s power plants, while China suspended the approval process for new nuclear plants pending the revision of safety procedures.
Three months before the Japanese earthquake the Paris-based Nuclear Energy Agency (NEA) published a report which concluded that for the public nuclear energy is no longer “...a quasi-ideological “yes” or “no” issue..........nuclear is now being viewed on its merits as a solution to questions of security of supply, cost stability and reductions in greenhouse gas emissions.” The Fukushima accident demonstrated the fragility of such assumptions.
Nuclear Fuel Cycle. The underlying principle of nuclear power generation is controlled nuclear fission releasing energy. It is the practical demonstration of Albert Einstein’s 1905 formula , E = Mc2 , relating energy (E), mass (M) and the speed of light (c). The energy released from this fission heats water into steam which, in turn, powers a turbine to generate electricity.
The fissile material used for this process is the uranium isotope U-235. The concentration of the two main uranium isotopes, U-235 and U-238, in naturally occurring uranium ore is about 0.1%. Of this uranium, only 0.7% is the U-235 isotope. For use as a reactor fuel, the U-235 concentration has to be between 3% and 5%. The first stage of this process is performed at the mining site by passing oxygenated groundwater through the mined ore. The resulting uranium...