tungtvannsreaktorer

Tungtvannsreaktorer, also known as heavy water reactors, are a type of nuclear reactor that uses heavy water as both a moderator and coolant. Heavy water, chemically denoted as D2O, is water in which the hydrogen atoms are replaced by deuterium, an isotope of hydrogen with one proton and one neutron. This slight difference in atomic structure gives heavy water unique properties that make it particularly suitable for nuclear fission.

The primary advantage of using heavy water in a reactor is its exceptional neutron moderation capability. Heavy water absorbs very few neutrons, allowing a nuclear chain reaction to be sustained with natural uranium as fuel. This means that heavy water reactors do not require enriched uranium, which is a more complex and costly fuel to produce. This characteristic makes them an attractive option for countries that do not have advanced uranium enrichment facilities.

Canada has been a significant developer and operator of heavy water reactors, with the CANDU (CANada Deuterium Uranium) reactor design being the most prominent example. These reactors are known for their inherent safety features and their ability to be refueled while operating, which contributes to high capacity factors and efficient fuel utilization.

The heavy water moderator and coolant are kept under pressure to prevent boiling at operating temperatures. The fuel typically consists of natural uranium dioxide pellets encased in zirconium alloy cladding. The neutrons released during fission are slowed down by the heavy water, increasing the probability of further fission events and thus maintaining the chain reaction. Despite their advantages, heavy water reactors also have challenges, including the cost of producing heavy water and the potential for tritium production as a byproduct.