Watts Bar unit 2 (a Westinghouse 4-loop PWR) came online in 2016. There are differences between pressurized water reactor (PWR) and boiling water reactor (BWR) coriums. Light water is used as the primary coolant in a PWR. This also increases the capital cost and complexity of a PWR power plant. Canadian, Japanese, French, and German PWR suppliers use the vertical configuration as well. Pressurized water reactor (PWR) designs are less susceptible. PWR fuel bundles are about 4 meters long. PWR fuel bundles are about 4 meters in length. A new pressurised water reactor, the Rolls-Royce PWR 2, was designed for the "Vanguard" class. The design is a type of pressurised water reactor (PWR). The BWR concept was developed slightly later than the PWR concept. This property, known as the negative temperature coefficient of reactivity, makes PWR reactors very stable. One estimate put the radiation at 100 times that of a typical PWR. Multiple events named PWR Live have been staged since. A 20-year life extension is the strategic target for the Sizewell B PWR.