Nuclear energy can be generated in a variety of different ways. In the US, the most common type of reactor design is the Pressurized Water Reactor (PWR), followed by the Boiling Water Reactor (BWR). Worldwide, Pressurized Water Reactors account for the bulk of the nuclear fleet worldwide. There are, however, three countries that operate nuclear power plants where this is not the most common technology. These countries are Canada, the United Kingdom, and Japan.
Canada’s nuclear power generation fleet has exclusively utilized heavy-water technology, with the CANDU reactor being a Canadian invention. Instead of water, the reactor design uses heavy water as a which has the added benefit of being able to use natural (unenriched) uranium fuel. Canada’s mineral deposits include uranium, which means that there is no foreign dependence on fuel processing for Canada’s reactors.
The United Kingdom has preferred gas-cooled reactors for its fleet of power generating nuclear plants, though there have been other technologies used such as the Magnox reactor at Dungeness A. Plans for a next-generation Pressurized Water Reactor, the so-called European Pressurized Reactor developed by Areva, EDF, and Siemens, are being developed and have been approved for a new nuclear power plant in the UK.
Japan’s nuclear fleet has seen rapid decommissioning following the 2011 earthquake and tsunami that led to the Fukushima nuclear disaster. Japan has relied on a mix of Pressurized Water Reactors and Boiling Water Reactors, the capacity being skewed towards the latter. The fundamental difference in reactor design between the Pressurized Water Reactor and the Boiling Water Reactor is that the BWR produces steam directly in the reactor core and does not rely on a heat exchanger to generate steam.
Each of the different designs has its own safety concerns, though the most common technologies the PWR and BWR reactors rely most heavily on active safety systems because of their nature of producing residual heat which must be properly managed even after a shutdown. Though there is no perfect reactor, most risks are mitigated.
