Why is heavy water a better moderator

Another potential issue with using graphite as a moderator is its ability to oxidize in the presence of air, and its low strength and density which could cause it to change dimensions in the reactor. Reactors that use graphite moderator include the RBMK , pebble bed reactors , and the magnox reactor.

Nuclear reactors can be either thermal or fast. Currently, almost all operating reactors are thermal and thus require a moderator to slow down fast neutrons to the thermal level so that nuclear fission can continue. Fast reactors are beneficial as they enhance the sustainability of nuclear power. This is because they have the ability to get more neutrons out of their fuel, can transform nuclear waste into products that decay more quickly, and they respond better to potentially catastrophic equipment failures.

However, they are more expensive, and they can overheat fairly easily. Fossil Fuels. Nuclear Fuels. Acid Rain.

Climate Change. Climate Feedback. Ocean Acidification. Rising Sea Level. No, Heavy Water is not radioactive. It is oxide of deuterium D 2 O which is stable isotope of hydrogen. Few Deuterium in Heavy Water gets converted to Tritium by absorbing a neutron in nuclear reactor. Tritium is a radioactive isotope of hydrogen having two neutrons in the nucleus. Further, some of the ionic impurities that are carried by heavy water as moderator or coolant also get activated in course of irradiation.

Hence the radio activity is observed in Heavy Water used in Nuclear reactors. A small quantity of heavy water is not harmful to human health. In fact, human body contains few grams of Heavy Water as natural abundance. Small quantities of Heavy Water have been used in clinical studies and treatment in infants, lactating women and adults without any reported adverse effect.

Since deuterium is a stable isotope , heavy water is not radioactive. In addition to being useful for nuclear reactors, heavy water has also been used in Canada to detect neutrinos from the sun at the Sudbury Neutrino Observatory , providing important insights to subatomic physics.

In nuclear fission reactors, the neutrons must be slowed down to ensure an effective fission chain reaction occurs. This process of slowing neutrons down is known as moderation , and the material that slows down these neutrons is known as a neutron moderator.

Heavy water is one of the two moderators that can be used which allow a nuclear reactor to operate using natural uranium. The other moderator is graphite. A heavy water reactor makes use of heavy water as its coolant and moderator. Deuterium works as a moderator as it absorbs fewer neutrons than hydrogen, which is extremely important as nuclear fission reactions require neutrons to carry out their chain reactions.

CANDU reactors utilize heavy water as their moderator and thus do not require enriched uranium, rather uranium in its natural state can be used. The cost of the heavy water is a significant part of the building cost of a heavy water reactor , but makes the reactors cheaper to operate since uranium enrichment is unneeded.

Technically speaking, deuterium is not "made" in a specific process, rather molecules of heavy water are separated from large quantities of water containing H 2 O or singly deuterated water in the Girdler sulfide process which will be discussed in detail in the next two paragraphs.

The water that is not heavy is discarded and is known as "depleted water". An alternative method exists when water is electrolyzed to make oxygen and hydrogen that contains normal gas , along with deuterium. Producing heavy water requires advanced infrastructure, and heavy water is actively produced in Argentina, Canada, India, and Norway. The largest plant was the Bruce Plant in Canada, but has shut down.

Technically, there is a slight difference in the boiling points of heavy water and water, so this difference could be taken advantage of when extracting heavy water. This would require a lot of fuel or electricity , so instead facilities exploit chemical differences between the two.

The most important chemical method for producing heavy water is the Girdler sulfide process.