Why natural uranium is used as a fuel in heavy water reactors?
Advantages and disadvantages. The use of heavy water as the moderator is the key to the PHWR (pressurized heavy water reactor) system, enabling the use of natural uranium as the fuel (in the form of ceramic UO2), which means that it can be operated without expensive uranium enrichment facilities.
Why is heavy water used as a moderator in a nuclear reactor?
Moderator is required in a Nuclear reactor to slow down the neutrons produced during the fission reaction so that the chain reaction can be sustained. Heavy Water is an excellent moderator due to its high moderating ratio and low absorption cross section for neutrons.
Why in a natural uranium reactor heavy water is preferred as a moderator over ordinary water?
Heavy water is basically used as a moderator in nuclear reactors to slow down the neutrons so that they are captured and become effective to bring about the fission reaction. The main reason why heavy water is used as a moderator is because it captures less neutrons than the normal water.
Why can a heavy water moderated reactor use a lower enrichment uranium fuel than a light water moderated reactor?
Heavy water reactors use D2O as the coolant/moderator, allowing natural, unenriched uranium to be used as the fuel. This is possible because D2O absorbs fewer neutrons than H2O.
How is heavy water used in reactors?
Heavy water is used as a moderator in some reactors because it slows down neutrons effectively and also has a low probability of absorption of neutrons.
What does a heavy water reactor do?
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.
Why is heavy water used?
Heavy water is used in certain types of nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238, which captures neutrons without fissioning. The CANDU reactor uses this design.
What is the function of heavy water in a nuclear reactor Mcq?
Heavy water is used in nuclear reactors because it acts as a moderator in slowing down the neutrons that are produced during the fission reaction.
Why is heavy water used as a moderator and not ordinary water?
Water containing significantly more than the natural proportions (one in 6,500) of heavy hydrogen (deuterium, D) atoms to ordinary hydrogen atoms. Heavy water is used as a moderator in some reactors because it slows down neutrons effectively and also has a low probability of absorption of neutrons.
Can ordinary water be used as moderator?
Ordinary water is not used as a moderator in nuclear reactors because. of its corrosive action on metallic parts of the nuclear reactor. Ordinary water absorbs fast moving neutrons, thus stopping the process of nuclear fission.
Why are heavy water reactors less widely used than light water reactors?
Heavy water moderates the reactor less efficiently than the normal, light water does. What that means for the reaction is that the deuterium, the heavy isotope of hydrogen, absorbs fewer neutrons, which are released spontaneously by the fuel in the system.
Why is water a better moderator than graphite?
Water and carbon (graphite) are commonly used moderators. Water is a good moderator, but the hydrogens in the water molecule have a fairly high cross section for neutron capture, removing neutrons from the fission process. Heavy water, used as moderator in Canadian reactors, avoids this loss.
Why is heavy water used as a moderator in CANDU reactors?
Most commercial reactor designs use normal water as the moderator. Water absorbs some of the neutrons, enough that it is not possible to keep the reaction going in natural uranium. CANDU replaces this “light” water with heavy water . Heavy water’s extra neutron decreases its ability to absorb excess neutrons,…
What is the difference between heavy water and moderator water?
The moderator heavy water system has a separate heat exchanger with circulation system for cooling the moderator. Courtesy Canadian Nuclear Association The CANDU reactor’s cooling water tubes are pressurized to 1525 pounds per square inch, lower than pressurized water designs.
What type of uranium is used in a CANDU reactor?
CANDU reactors use natural uranium as their nuclear fuel. Natural uranium is composed of about 0.7\% uranium-235, and the remaining 99.3\% is mostly uranium-238 which cannot directly be used in a fission process to obtain energy.
How does a CANDU work?
The CANDU design consists of a horizontal calandria (Vessel) which has tubes for the fuel rods and cooling water (heavy water). Around these tubes is heavy water, which acts as the moderator to slow down the neutrons. Heavy water consists of 2 atoms of deuterium (a non-radioactive isotope of hydrogen) and 1 atom of oxygen.