Page "Nuclear reactor" Paragraph 25

:: A Canadian design ( known as CANDU ), these reactors are heavy-water-cooled and-moderated Pressurized-Water reactors.

Instead of using a single large pressure vessel as in a PWR, the fuel is contained in hundreds of pressure tubes.

These reactors are fueled with natural uranium and are thermal neutron reactor designs.

PHWRs can be refueled while at full power, which makes them very efficient in their use of uranium ( it allows for precise flux control in the core ).

CANDU PHWRs have been built in Canada, Argentina, China, India, Pakistan, Romania, and South Korea.

India also operates a number of PHWRs, often termed ' CANDU-derivatives ', built after the Government of Canada halted nuclear dealings with India following the 1974 Smiling Buddha nuclear weapon test.