Nuclear power reactors

Nuclear power supplies over 16 per cent of the world's electricity from 439 reactors. These reactors save 2.5 billion tonnes of CO2 per year, equivalent to the Kyoto protocol reduction targets for all countries.

The United States is the biggest user with 104 reactors, followed by France with 59, Japan with 56 and the United Kingdom with 23. About 30 countries produce electricity from nuclear reactors. At March 2008 there were about 34 power reactors are currently under construction in 11 countries notably China, South Korea, Japan and Russia; and more are in the planning stages. For details, see the World Nuclear Association.

The structure of a nuclear power plant in many aspects resembles that of a conventional thermal power station, since in both cases the heat produced in the boiler (or reactor) is transported by some coolant and used to generate steam. The steam then goes to the blades of a turbine and, by rotating it, the connected generator will produce electric energy. The difference between a conventional and a nuclear power plant is how heat is produced. In a fossil plant, oil, gas or coal is fired in the boiler, which means that the chemical energy of the fuel is converted into heat. In a nuclear power plant, however, energy that comes from fission reactions is utilised.

Approximately 80 per cent of the commercial reactors operating are cooled and moderated with ordinary water and are known as light water reactors (LWRs). The two major LWR types are pressurised water reactors (PWRs) and boiling water reactors (BWRs). Most of the remaining 20 per cent of reactors are cooled by heavy water or gas. PWRs and BWRs have evolved to become mature, safe and reliable technologies in widespread use. This evolutionary process has led to the current models being described as Generation III reactors.

Evolution of nuclear power reactors

  • Generation 1
  • Generation II
  • Generation III and III+
  • Future is Generation IV

Generation IV reactors

The next generation of reactors are referred to as generation IV reactors. These reactor designs are under development, and it is not expected that a generation IV reactor will be in operation before at least 2020.

The Generation IV International Forum (GIF) is aimed at advancing the development of six of the most promising next generation nuclear power reactor technologies.

The new reactor designs promise to increase safety and reduce radioactive waste production and proliferation risks.

The Generation IV roadmap, developed by GIF, identifies the following six advanced reactor designs and the underpinning research required to develop them:

  • Gas-Cooled Fast Reactor System (GFR)
  • Lead-Cooled Fast Reactor System (LFR)
  • Molten Salt Reactor System (MSR)
  • Sodium-Cooled Fast Reactor System (SFR)
  • Supercritical-Water-Cooled Reactor System (SCWR)
  • Very-High-Temperature Reactor System (VHTR).