What is heavy water
Heavy water is deuterium water with the formula D2O. A molecule of heavy water is composed of two heavy hydrogen atoms and one oxygen atom, its molecular formula is D2O, the relative molecular mass is 20, heavy water in nature is less distributed, in ordinary water about 0.015% heavy water, due to the small content, difficult preparation, it is more important than gold.
What can heavy water be used for
The main use of heavy water is as a "moderator" in nuclear reactors, reducing the speed of neutrons, controlling the nuclear fission process, and also as a coolant. Heavy water and deuterium are valuable tracers in the study of chemical and physiological changes, for example, irrigating trees with dilute heavy water can measure water moving in these plants by tens to tens of meters per hour. The amount of deuterium in the urine of people who have drunk large amounts of dilute heavy water shows that water molecules stay in the body for an average of 14 days. Using deuterium instead of ordinary hydrogen can study the process of digestion and metabolism in plants and animals. Dense or pure heavy water cannot sustain plant and animal life, and the lethal concentration of heavy water for ordinary plants and animals is 60%.
The special value of heavy water is reflected in the application of atomic energy technology. To make a powerful nuclear weapon, heavy water is needed as a moderator in the nuclear fission reaction.
When using NMR analysis, if the solvent is water and the object of study is hydrogen, heavy water can be used as the solvent. Neutron moderators: Some nuclear reactors use heavy water to slow down neutrons and give them a chance to react with uranium. Light water can also be used as a moderator, but because light water absorbs neutrons, a light water reactor must use enriched uranium, not ordinary uranium, or it will not reach critical mass. Heavy water reactors not only use ordinary uranium, but also convert uranium-238 into bomb-making plutonium. India, Pakistan, Israel and North Korea all make nuclear fuel in this way. To prevent the spread of nuclear weapons, the production and sale of heavy water is restricted in many countries.
Heavy water has important uses in cutting-edge technology. Electrolysis of heavy water can produce heavy hydrogen, which is the raw material for hydrogen bombs. More importantly, heavy hydrogen can emit huge amounts of energy when undergoing nuclear fusion reactions, and will not pollute the environment. Some people calculate that if the heavy hydrogen in seawater is used for thermonuclear reaction to generate electricity, the total energy is equivalent to the entire ocean turned into oil.
Can heavy water be drunk
Although heavy water is a valuable resource in cutting-edge technology, it is harmful to people. People can not drink heavy water, microorganisms, fish in pure heavy water or water containing more heavy water (more than 80%), as long as a few hours will die. On the other hand, light water containing very little heavy water, such as snow, can stimulate biological growth.
It is generally believed that heavy water is not toxic, but some metabolisms in the human body require light water, so if you drink only heavy water, you will get sick. Because D in heavy water has one more neutron than H, D is twice as heavy as H, resulting in certain changes in its chemical properties and substantial changes in its physical properties. The various bonds of D are stronger than those of H, and the transfer rate of heavier D will be much slower than that of H, resulting in a deceleration of the chemical reaction on D and interference with normal metabolism of the organism.
Heavy water extraction method
About one in 3,200 of the water on Earth is semi-heavy water (HDO). Semi-heavy water can be extracted from ordinary water by electrolysis and distillation, or chemically. Chemical methods can be used because heavy hydrogen and ordinary hydrogen atoms react at different rates due to slightly different masses. When the concentration of semi-heavy water in water reaches a certain level, heavy water will slowly appear due to the exchange of hydrogen atoms between water molecules. Electrolysis, distillation and chemical methods can also be used to reextract pure heavy water from semi-heavy water. However, the energy required for electrolysis and distillation can be very large, so normally only chemical methods are used for this step.