The main advantages of LWRs are that they are relatively simple and compact. They have been developed over a period of more than 50 years and so the experience has led to the development of robust and efficient plants. They do, however, require the use of enriched fuel and the steam conditions are such that their thermal efficiencies are not as high as some gas-cooled plants. However, they are capable of achieving relatively high fuel burnup so their efficiency in terms of fuel utilisation is good.

LWRs have also proved themselves to be flexible plants, and can contribute to load following and frequency control. PWRs using grey rods and BWRs can load follow over their complete cycle. PWRs which use black rods can also load follow on a daily basis for most of their cycle, but it can be more difficult towards the end of a cycle, not because of any limitations on the reactors, but because of the need to process the large quantities of water involved in making changes to low boron concentrations. The limitation is then associated with the capacity of the boron recycle system or waste water processing system.

Given the time that they have been in operation we now also have experience with the decommissioning of the plants and because of their compact design they have proved to be relatively straightforward to decommission.

The design relies on a high integrity pressure vessel, which potentially limits the size of plant that can be constructed. In addition at present there are relatively few suppliers of large high integrity vessels and their components. The integrity requirements mean that the vessels are factory constructed and have to be transported as a unit. However, the size limitation is probably not an issue since vessels accommodating cores capable of supporting electrical outputs of at least 1800 MW(e) are currently envisaged.