Nuclear energy: Beneficial uses
THE word "Nuclear" disallows people to not think deeply about its benefits. However, radioactive and stable isotopes are used peacefully throughout the world in many sectors, including agriculture, medicine, industry, and research. Isotopes are different types of atoms (nuclides) of the same chemical element, each having a different number of neutrons. In many applications, isotopes have no substitute and in most others, they are more effective and cheaper than alternative techniques or processes. About 50 countries have significant isotope production capacities, and many others have smaller capacities.
The use of radiation and isotope techniques in agriculture has played an important role in increasing food production over the world. More than 2000 improved crop varieties have been developed using nuclear techniques. Bangladesh Institute of Nuclear Agriculture has so far released 42 mutant varieties of different crops (rice-7, mustard-6, groundnut-4, mungbean-7, lentil-4, chickpea-4, sesame-1, jute-3, tomato-5, black gram-1). Physical mutagens such as gamma rays, x-rays, and chemical mutagens such as ethyl methane sulphonate, sodium azide etc. are utilised for bringing about genetic changes within a crop variety, in terms of earliness, nutritional quality, disease resistance, water, salinity, temperature stress tolerance and other characters.
Radioisotopes (32P, 35S, 14C, 65Zn, etc.) and stable isotopes (15N, 18O, 2H etc.) are widely used in the study of fertiliser use efficiency and uptake of nutrients and their physiological functions in plants, measurement of biological nitrogen fixation by legumes, exploration of water resources and hydrology, understanding of biochemical pathways, dynamics of nutrients in soil including loss by leaching, and insecticide use and agrochemical residue studies. Using isotopic tracer technique in fertiliser studies, the amount of added fertiliser take up by plants can be indicated, and the method of application, placement and management can be effectively evaluated. Radioisotopes 14C and 32P are used in translocation -- movement of photosynthetic materials -- and root growth studies. At very low doses, irradiation inhibits regrowth or sprouting in stored potatoes, onions and garlic, delays ripening and over-ripening of fruits, and substitutes chemical fumigants used to control insect pests in stored rice, wheat flour, pulses, gram flour (besan), dry fruits, nuts, spices, dry fish etc. At high doses irradiation pasteurises or retards spoilage of meat, poultry, and fishery products by killing bacteria. At still higher doses, irradiation can improve quality and microbial safety of spices and dry herbs. Radiation processing leaves no residue in food and it is an eco-friendly technology.
Radioimmunoassay and related nuclear techniques are also widely used in the study of animal nutritional and reproduction problems, and animal disease diagnosis.
Radioactive dating gives us an approximate age of rock or material containing radioactive atoms. For example, for a measurement of a fraction of uranium atom, which has decayed into lead, knowing the half-life of uranium tells us how old the rock is. Metal casting can be tested for cracks by putting them in baths of radioactive salts. The castings are then inspected for radioactivity to find out any penetration of salts into cracks. Absence of salt penetration indicates absence of cracks. The optical microscopes developed in physics are extensively used in the study of biological samples.
Electron microscope, X-rays and radioisotopes are used widely in medical science. Gamma rays emitted by the radioisotopes can be used in the treatment of cancer. These radiations tend to destroy cancerous cells and the way can arrest the spreading of the cancerous cells. 60Co is used in the treatment of tumours and cancers. In order to find if blood is circulating to a wound or not, a radioactive isotope is injected into the blood stream. After a time period, blood from the wound is examines for its radioactivity. If no radioactive isotope is detected, it means that passage of blood is hindered.
32P is used for relief in leukemia and 132I is used in the treatment of goiter.
Dr. Md. Tariqul Islam is a senior scientific officer with Crop Physiology Division, Bangladesh Institute of Nuclear Agriculture, Mymensingh.
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