General Science : Heavy Water

Deuterium Oxide (or) Heavy Water Heavy Water (D2O) is used as a moderator and coolant in the Pressurised Heavy Water Reactors (PHWRs). There often a misconception that since it is used in nuclear reactors, it is radioactive. No radioactivity is associated with it. Deuterium, also called Heavy Hydrogen is a stable isotope of Hydrogen with a natural abundance of approximately one atom in about 7000 of Hydrogen ( about 150 ppm). Heavy Water (D2 O) is a compound of Deuterium and Oxygen. It has a great similarity in its physical and chemical properties to ordinary water but its nuclear properties display a significant variation, which makes it an extremely efficient material for use as moderator & coolant in a nuclear reactor. Heavy Water is non-radioactive. Moderator is a substance required in a Nuclear Reactor to slow down the Neutrons produced in the fission reaction in order to sustain the chain reaction. In India it is used in Pressurised Heavy Water Reactors. Heavy Water is a good moderator, having excellent slowing down power and low absorption cross-section for neutrons. Heat generated by fission in reactor is efficiently removed by the coolant. Heavy Water (primary coolant) transports heat to water (secondary coolant) for generating of steam for running steam turbines. Steam turbines drive generators to generate electricity. A large potential for non-nuclear applications of Deuterium/Heavy Water are emerging in the fields of Medical/Life Science and Communication/Microelectronics. Heavy Water Baord (HWB), in the Department of Atomic Energy, Government of India has also collaborated with Board of Radiation & Isotope Technology (BRIT) for development of biological applications of deuterium. HWB also supplies of deuterium gas mixture for production of low water peak optical fiber to leading Indian optical fiber industry. 

 HOW HEAVY WATER IS PRODUCED IN INDIA ? The first generation heavy water plants included setting up of Bithermal H2 S, H 2 O exchange plant based on wholly indigenous efforts by parallel constructing the plants based on monothermal NH3 – H2 exchange process with the assistance from foreign collaborators/suppliers. The second generation plants with higher plant capacity were taken up for construction using indigenous engineering capabilities. The plants at Heavy Water Plant , Manuguru, Andhra Pradesh based on H2 S water Exchange Process and Heavy Water Plants at Thal and Hazira based on Ammonia – Hydrogen Exchange process were thus put into commercial operations. Heavy Water has a unique property of thermostabilisation of several biological molecules, cells, tissues etc. Experiments carried out for thermostabilisation of Oral Polio Vaccine (OPV) has clearly indicated that heavy water suspended vaccine can withstand 37oC for seven days without loss of any potency. This would be of enormous importance to a tropical country like India, where a break in the cold-chain during transportation or storage can create loss of potency of OPV. Therefore, supplementing the OPV by using heavy water during its manufacture can bring about dramatic improvement in the retention of vaccine potency even if there is a loss in the cold-chain when it reaches the remote areas of this country. Besides OPV, even the vaccines used in the poultry, cattle and domestic animals can also be prepared in heavy water for enhanced thermostabilisation property, which again will have enormous applications in India. In another application of Heavy Water, several drugs (already in regular clinical practice) , deuteration have been shown to undergo favourable alterations in respect of their pharmacokinetics leading to enhancement of clinical efficacy or moderation of adverse effect. Use of heavy water in such clinical medicines will be pertinent to the knowledge of disease pattern and drug prescription profile. There is growing evidence from the diverse approaches, demonstrating the potential of heavy water as an adjunct to chemotherapy, photo dynamic therapy and radiation therapy of cancer. This is an area which has been pursued vigorously in several laboratories worldwide and for potential uses also in the context of types and nature of malignancy prevent in the Indian population. Heavy water in small doses can also be used for bringing down blood pressure due to its anti-hypersensitive properties. It is reported to be anti-mutagenic and radio-protective. This opens up new avenues in these fields. Several algae and fungi can grow well in heavy water and thereby leading to the biogenesis of important molecules fully deuteriated, which could be precursors of high value products with applications in bio-tehcnologies. Heavy water has also shown to be a good moderating molecule on human body with properties which retard the process of ageing and can be used at low doses for therapeutics purposes. Heavy Water is also used as a tracer for large number of studies in humans, in the areas of clinical nutrition, physiology and medicine. Low doses of heavy water have not only shown to be safe among infants, adults, and pregnant women. It is shown to have beneficial properties. One more area of interest is the use of heavy water in the study of energy metabolism for soldiers working in high altitude battlefields. Heavy Water and H2 18O is used as double- labeled water for the determination of total energy expenditure and to calculate the energy intake and its distribution. This is particularly useful to the high altitude climbers or battalions located in such places as Siachin Glacier. The defence Institute of Physiiological Studies and Allied Sciences under the defence Research & Development Organisation has sought this kind of research in the supply of such Double-labeled water. Besides this H2 18O is also used in medical cyclotron application. What are the new uses of Deuterium?: 1) Preservation of oral polio vaccines; deuterated drugs for enhancement of biological efficiency 2) deuterated optical fibers to enhance transmission efficiency; deuterium substituted lubricants for enhancing life of lubricants 3) deuterated compounds as tracers in studies of reaction mechanisms 4) deuterted polymers with improved mechanical & chemical properties 5) Deuterarted photosensitive plastics with increased optical recording density 6) Deuterated metal oxide semiconductor for increased leakage current resistance 7) Applications in thermo stabilization of vet-vvaccines, tissue preservation & diagnostic studies 8) Doubly Labeled Water (DLW) having certain concentration of deuterium and O-18 is used for measuring energy expenditure , total body water content etc. 18 O (Oxygen-18 isotope) is used in Positron Emission Tomography (PET) used for typically detection and staging malignancies. This isotope has demand in Atomic Energy Department and Defence Research & Development Organisation.