The main emphasis in the development of ALWRs has been on the production of large plants. This provides benefits in terms of economies of scale as well as minimising the number of sites required. However, there has been a renewal of interest in small and medium reactors (SMRs); SMRs are generally defined as being reactors of less than about 600 MW(e).

The renewed interest in SMRs is mainly focussed on issues associated with the introduction of nuclear generation into countries or areas with smaller distribution grids, and the lower initial investment costs. The smaller SMRs can effectively be factory constructed. One example is barge-mounted units, which can be constructed in a shipyard and then towed to their final location. SMRs also tend to be simpler than large reactors and can make greater use of passive systems.

As with all electricity generation plants the economics of SMRs is important. On one hand the small size mitigates against economies of scale while the simpler designs and the ability to factory construct modular plants should reduce costs. One key consideration could be the initial investment cost. The smaller unit price may make it easier to provide the investment needed to get a programme of reactors started as well as making them more appropriate for markets where the rate of growth of demand is lower.

10.10 Sources of further information

The best sources of further information on LWRs are the websites of the international organisations involved in nuclear power because the information is regularly updated. In particular the IAEA (http://www. iaea. org/) provides safety standards and design requirements that form the basis for the national regulation of most countries. In addition they also provide extensive information on nuclear technology for both existing and developing reactor designs. OECD’s Nuclear Energy Agency (http://www. oecd-nea. org/) also provides extensive information, as does the World Nuclear Association (http://www. world-nuclear. org/).

Another excellent source of information on LWRs is the USNRC (http://www. nrc. gov/). This includes training material as well as information relating to existing and proposed plants. For the new plants this is not confined to US plants since it contains information on all the plants that are going through the design certification process for new plants. Similarly there is considerable information available on the plants going through the UK Generic Design Assessment process via the Office of Nuclear Regulations Website (http://www. hse. gov. uk/ newreactors/index. htm).