CANDU

The CANDU power reactor is a Pressurized Water Reactor using heavy water, (i.e., pressurized heavy water reactor (PHWR)), initially developed in the late 1950's in Canada. CANDU is an acronym for "CANada Deuterium Uranium".

This design is relatively safe from a nonproliferation standpoint, as it produces little plutonium, and that plutonium is rich in ²⁴⁰Pu, an isotope highly undesirable for bombs.

Since the fuel and heating elements are modular, the reactor can be refuelled without completely shutting it down.