India is a large producer of radioisotopes. The radioisotopes are produced in the research reactors at Trombay, accelerator at Kolkata and various nuclear power plants. BARC, BRIT, CAT and VECC are the organizations of DAE which are engaged in the development of radiation technologies and their applications in the areas of health, agriculture, industry and research.
DAE is working in close co-operation with other organizations of the Government of India to widen the reach of these technologies for the benefit of the common man. Remarkable progress was achieved in applications of Radioisotopes and Radiation Technology in the areas of nuclear agriculture, food preservation and industry.
The research reactors APSARA, CIRUS and DHRUVA at Trombay are utilized for basic and applied research, isotope production, material testing and training for human resource development.
APSARA and DHRUVA reactors are extensively used for basic and applied research, radioisotope production, material testing and operator training. After refurbishing, CIRUS went into operation at 20 MWt. The work on the 20 MWt light water cooled, heavy water reflected low enriched uranium fuelled pool type research reactor made progress.
The nuclear agriculture programme of BARC covers development of high yielding crop seeds using nuclear techniques, fertilizer and pesticide related studies, radiation processing of food items and other areas. ecently, two varieties of groundnut namely TG-37A and TPG-41 developed by BARC were notified for commerical cultivation. So far, a total of 24 varieties of high yielding crops were developed, released and notified for commercial cultivation by Government of India.
Preservation of Food and Hygienization:
Preservation of food by radiation processing involves controlled application of energy of ionizing radiation such as gamma rays, X-rays and accelerated electrons to agricultural commodities and food products.
KRUSHAK (Krushi Utpadan Sanrakshan Kendra), a technology demonstration unit of BARC, set up for low dose applications of radiation for food preservation became operational at Lasalgaon near Nashik. The plant radiation processed onion, pulses, rawa and turmeric. Radiation Processing Plant, Vashi operating since January 2000, performed very well with an enlarged scope of processing of products.
The major thrust given to the area of setting up of new radiation processing plants for medical, food related and allied products has shown very encouraging results in the recent times and about eight private parties signed the MoU with BRIT for setting up new plants. The first of these (M/s. Organic Green Foods Ltd., Kolkata) is expected to be operational shortly.
BRIT also developed an install-and-operate type irradiator for radiation processing of food items. The plant was undergoing evaluation tests. DAE is working with the Ministry of Health for notifying items for radiation processing for approval of addtional items and other related issues.
Nuclear & Biotechnological Tools:
At Trombay, tissue culture and recombinant DNA technology (transgenic plants) were employed for plant improvement. Important contributions were also made in the micropropagation of banana, pineapple, Acacia Victoriae and other economically useful plants. Several pesticides were extensively evaluated for their degradation in the environment using labelled compounds.
As a part of health care programme, BARC’s 1800 m3/day Reverse Osmosis (RO) Desalination Plant coupled with Nuclear Power Plant at Kalpakkam is doing extremely well.
The construction of the adjoining desalination plant based on Multi-Stage Flash (MSF) evaporation process made progress. A 30 m3/day desalination unit based on low temperature evaporation (LTE) process was integrated with CIRUS research reactor to demonstrate sea water desalination using waste heat from the research reactor.
BARC built a 30 m3/day RO plant in Satlana Village of Jodhpur District for producing drinking water from bore well brackish water source. The technology for online domestic water purifier based on ultrafiltration polysulfone membrane for producing bacteria free safe drinking water was transferred to eight parties, out of which two have already launched their products in the market.
Radioisotopes and their formulations find wide applications in diagnosis, therapy and healthcare. BARC supplies reactor produced radioisotopes to BRIT which processes them and produces various products for use in healthcare and industry.
BRIT produces and supplies a large number of radioisotope products including radiopharmaceuticals, immunoassay kits, technetium-99m generators, radiochemicals, labeled compounds, labeled nucleotides and luminous compounds.
A method for the preparation of potassium 32P-phosphonate was developed, procedure standardized and the product was supplied to Central Water Resources Development Institute, Calicut.
BRIT expects to achieve production and supply of about 42,000 consignments of various types of radioisotopes, equipment and allied products, valued at about Rs 23.50 crore (as against Rs 21.67 crore, previous year) during 2003-2004.
Iodine-125 based miniature brachy therapy source developed by BARC was tried for the first time for treatment of eye cancer at Sankara Netralaya, Chennai.
To provide a low cost alternative teletherapy unit for the expensive teletherapy unit being imported, the development of cobalt-60 Teletherapy Machine was completed at BARC.
The Medical Cyclotron with Positron Emission Tomography (PET) scanning facility set up at Radiation Medicine Centre of BARC, continues to produce F-18 labelled FDG molecules for diagnosis of cancer as well as cardiac disorders.
A digital medical imaging system based on a Charge Coupled Device (CCD) was developed for the first time in the country along with a variety of image processing software.
Sterilization of Medical Products:
Radiation sterilization is a highly effective technology for sterilization of medical products. BRIT’s ISOMED plant at Trombay, has been operating for over three decades, providing radiation processing service of medical products to pharmaceutical industry. The plant continued to offer gamma sterilization services to nearly 1600 customers spread all over the country. About 15,000 cubic metres of different types of products were sterilized during the year.
Radiation and environment
Many forms of “radiation” are encountered in the natural environment and are produced by modern technology. Most of them have the potential for both beneficial and harmful effects. Even sunlight, the most essential radiation of all, can be harmful in excessive amounts. Most public attention is given to the category of radiation known as “ionizing radiation.” This radiation can disrupt atoms, creating positive ions and negative electrons, and cause biological harm. Ionizing radiation includes x-rays, gamma rays, alpha particles, beta particles, neutrons, and the varieties of cosmic rays.
All ionizing radiations, at sufficiently large exposures, can cause cancer. Many, in carefully controlled exposures, are also used for cancer therapy. Whether harmful or beneficial, exposures to ionizing radiation have been an inevitable part of the environment throughout the Earth’s history. The nucleosynthesis processes that produced the elements created both stable and unstable nuclides. The unstable nuclides with very long half-lives, together with their radioactive progeny, constitute the natural radioactivity on Earth today. In addition, violent processes in the sun and elsewhere lead to the bombardment of the Earth by cosmic rays. Thus, radiation is an old and familiar, if unrecognized, pollutant.
However, human awareness of radioactivity and ionizing radiation has only a 100-year history starting with the discovery of x-rays and radioactivity. The first evidence that ionizing radiation could do harm came within months after the discovery of x-rays, when an early x-ray worker developed injuries to his skin. Serious efforts to understand and control radiation exposures started in the 1920s and greatly expanded during and after World War II.
Information on the effects of radiation comes from studies of exposed groups and individuals, from animal experiments, and from studies at the cellular and molecular level. It is now well established that ionizing radiation has both prompt and delayed effects. At very high radiation exposures, death will occur within several months or less. At moderate levels, radiation exposure increases the chance that an individual will develop cancer, with a time delay of ten or more years for most cancers. At low levels, the cancer risk decreases, but the relationship between cancer risk and the magnitude of the exposure is uncertain.
Other effects of radiation, in part inferred from animal experiments, include an increased risk of genetic defects and, for exposures of the fetus before birth, of mental retardation. In terms of frequency of occurrence and severity of effects, cancer is the most serious consequence and receives the greatest attention.
Man made radiation sources
In general, the following man-made sources expose the public to radiation (the significant radioactive isotopes are indicated in parentheses):
- Medical Sources (by far, the most significant man-made source)
- Diagnostic x-rays
- Nuclear medicine procedures (iodine-131, cesium-137, and others)
- Consumer Products
- Building and road construction materials
- Combustible fuels, including gas and coal
- X-ray security systems
- Fluorescent lamp starters
- Smoke detectors (americium)
- Luminous watches (tritium)
- Lantern mantles (thorium)
- Tobacco (polonium-210)
- Ophthalmic glass used in eyeglasses
- Some ceramics
To a lesser degree, the public is also exposed to radiation from the nuclear fuel cycle, from uranium mining and milling to disposal of used (spent) fuel. In addition, the public receives some minimal exposure from the transportation of radioactive materials and fallout from nuclear weapons testing and reactor accidents (such as Chernobyl).
Nuclear reactor accidents
Chernobyl is considered the world’s worst nuclear disaster to date. It occurred on April 26, 1986, when a sudden surge in power during a reactor systems test resulted in an explosion and fire that destroyed Unit 4. Massive amounts of radiation escaped and spread across the western Soviet Union and Europe. As a result of the disaster, approximately 220,000 people had to be relocated from their homes.
The partial meltdown at Three Mile Island Unit 2 is considered the most serious nuclear accident in U.S. history, although it resulted in only small radioactive releases. Coolant flow blockage in two fuel channels led to the partial meltdown of two fuel assemblies at Fermi Unit 1.
Effects of non ionizing radiation
Different biological effects are observed for different types of non-ionizing radiation. A difficulty is that there is no controversy that the upper frequencies of non-ionizing radiation near these energies (much of the spectrum of UV light and some visible light) is capable of non-thermal biological damage, similar to ionizing radiation.
Health debate therefore centers on the non-thermal effects of radiation of much lower frequencies (microwave, millimeter and radiowave radiation). The International Agency for Research on Cancer recently stated that there could be some risk from non-ionizing radiation to humans. But a subsequent study reported that the basis of the IARC evaluation was not consistent with observed incidence trends. This and other reports suggest that there is virtually no way that results on which the IARC based its conclusions are correct.