Technology Type

The Pressurized Heavy Water Reactor (PHWR) is the third most common nuclear reactor type, with 47 units operating worldwide as of 2023. It uses heavy water as both moderator and coolant, allowing it to operate with natural uranium fuel without enrichment. The design features a horizontal cylindrical vessel (calandria) containing fuel bundles, with typical operating temperatures of 290°C at 100 times atmospheric pressure. PHWRs are unique in their ability to be refueled during operation and are primarily deployed in Canada (where they're known as CANDU reactors), India, and several other countries. The technology represents about 7.8% of nuclear power reactors by number and 4.7% by capacity.