Generating electricity from nuclear power involves transferring the heat produced by a controlled nuclear fission reaction into a conventional steam turbine generator.The nuclear reaction takes place inside a core and surrounded by a containment vessel of varying design and structure. Heat is removed from the core by a coolant (gas or water) and the reaction controlled by a moderating element or “moderator”. Across the world over the last two decades there has been a general slowdown in building new nuclear power stations.This has been caused by a variety of factors: fear of a nuclear accident, following the events at Three Mile Island, Chernobyl and Monju, increased scrutiny of economics and environmental factors, such as waste management and radioactive discharges.

nuclear reactor designs: evolution and safety issues

At the beginning of 2005 there were 441 nuclear power reactors operating in 31 countries around the world. Although there are dozens of different reactor designs and sizes, there are three broad categories either currently deployed or under development.These are:

generation I: Prototype commercial reactors developed in the 1950s and 1960s as modified or enlarged military reactors, originally either for submarine propulsion or plutonium production.

generation II: Mainstream reactor designs in commercial operation worldwide.

generation III: Generation III reactors include the so-called “Advanced Reactors”, three of which are already in operation in Japan, with more under construction or planned. About 20 different designs are reported to be under development14, most of them “evolutionary” designs developed from Generation II reactor types with some modifications, but without introducing drastic changes. Some of them represent more innovative approaches.
According to the World Nuclear Association, reactors of Generation III are characterised by the following:

• a standardised design for each type to expedite licensing, reduce capital cost and construction time
• a simpler and more rugged design, making them easier to operate and less vulnerable to operational upsets
• higher availability and longer operating life, typically 60 years
• reduced possibility of core melt accidents
• minimal effect on the environment
• higher burn-up to reduce fuel use and the amount of waste
• burnable absorbers (“poisons”) to extend fuel life

To what extent these goals address issues of higher safety standards, as opposed to improved economics, remains unclear.