RADIATION TECHNOLOGIES AND NUCLEAR SAFETY ISSUES
RADIATION TECHNOLOGIES AND NUCLEAR SAFETY ISSUES
Radiation technology finds varied applications in the field of industry, healthcare, agriculture and research. India is a leading producer of radioisotopes in the world. The first indigenous cobalt-60 teletherapy source was prepared for use in treatment of cancer.
Desalination: B ARC has developed desalination technologies based on Multi-Stage Flash (MSF) evaporation. Reverse Osmosis (RO) and low temperature evaporation. To demonstrate viability of coupling nuclear reactor for desalination of sea water, B ARC has set up a 6,300cubic metre/ day combined MSF/RO Nuclear Desalination Demonstration Plant (NDDP) at Kalpakkam (Tamil Nadu).
Nuclear Agriculture: The BARC has successfully developed and released 24 high yielding crop varieties, including nine groundnuts, ten pulses and two mustard varieties, and one variety each of jute and rice. BARC has successfully developed green manure crop-Sesbania rostrata. Use of this variety is highly cost-effective for small farmers. The Centre has made good progress in developing hardened plants for Acacia Victoriae-a plant suitable for desert area. Using micropropagation technology, the BARC has standardised large-scale multiplication of pineapple.
Food Preservation: One of the beneficial applications of atomic energy is in preserving foods for extended periods. Food irradiation, as this process is known, is an important milestone in food preservation methodology since the successful development of canning in the 19th century. It has unique merits over conventional methods of preservation such as canning, dehydration, salting, etc., because this process does not lead to loss of flavour, odour, texture and other highly desirable attributes of fresh foods. Poor post harvest practices including inadequate storage and preservation facilities, as well as adverse climatic conditions, cause heavy losses in India’s agricultural and marine produce. Food irradiation promises to offer and effective means for minimizing these losses, thereby increasing their availability and stimulating exports.
- The application of low doses of radiation can arrest sprouting of potatoes and onions. As a result, storage losses due to sprouting of the tubers and bulbs and their dehydration can be reduced substantially.
- Low doses of radiation are effective in delaying the natural processes of ripening in fruits. Thus shelf life of mangoes can be extended by about a week and that of bananas up to two weeks.
- Furthermore, gamma radiation can eliminate the seed weevil, an insect that lodges deep inside the stone of the mango. This can be a satisfactory solution to vexing quarantine problem.
- Low dose irradiation completely kills or sterilizes the common grain pests, and even the eggs deposited inside the grains. Moreover, only a single radiation exposure of grains is sufficient for disinfestations.
- Irradiation can also serve as an effective process for disinfestation of certain pre-packed cereal products like atta, soji (rava) and premixes.
- By selective destruction of spoilage bacteria, moderate doses (200 kilorads) of radiation can extend the acceptability, and, in turn, marketability of iced fish by about two weeks.
- Combination processes with heat and radiation can also increase the shelf life at room temperature by several weeks. Besides, this is the only method of removal of pathogens from pre-packed frozen product.
- Single treatment of gamma radiation can make spices free of insect infection and microbial contamination without ‘ the loss of flavour components.
- The treatment can also be used for pre-packed ground spices and curry powders.
Food irradiation and Processing Laboratory of Bhabha Atomic Research Centre is one of the foremost laboratories of such kind in the world. The BRIT (Board of Radiation and Isotope Technology, Mumbai) has been carrying out radiation processing of spices and other products at the Radiation Processing Plant, at Navi Mumbai. Two research and development Radiation Processing facilities, at Trombay and Jodhpur (Rajasthan), have been licensed for radiation processing of food items.
Nuclear Medicine and Healthcare: The research at BARC has successfully developed Holmium-166-Hydroxy Apatite (HoHa) and Samarium-153-Hydroxy Apatite (SmHa) radiopharmaceuticals for the treatment of arthritis, and radiolabeling of phosphonates with Luthinium-177 for internalised radiotherapy.
Cancer Treatment and Research: In the field of diagnosis, treatment and research in cancer as well as in training and education, the Tata Memorial Centre (TMC), Mumbai, a grant- in-aid institution of DAE, is a leading organization in the country.
Industrial applications of Radioisotopes: The studies at BARC have immensely contributed to the detection and recharge conditions of ground water bodies in the Delang- Puri sector of coastal Orissa, determination of the origin of thermal waters in the geothermal areas in Madhya Pradesh, Uttar Pradesh and Himalayas, and establishment of the ancient course of the legendary ‘Saraswati’ river in Western Rajasthan.
Nuclear safety imposes strict demands on the containment of toxic and/or radioactive materials. Contamination of surrounding communities and environment is regarded as a never events from the perspective of plant design. Due to the energetic nature of nuclear reactions, nuclear material in a chain reaction is not necessarily stable from an energy output perspective, often requiring active control mechanisms to impose artificial stability.
Systems are often designed with multiple redundant backups to preclude system failure, with each independent system often designed with a conservative factor of safety in an attempt to preclude failure of the primary system in the first place. Elimination of common mode failure mechanisms is integral to the design of nuclear facilities; preventing cascade failures.
Many facilities are designed around the defence in depth approach, with multiple active and passive systems designed around preventing catastrophic failure. At the core of such a system one finds the Reactor Protective System, with ionizing radiation protection incorporated to protect facility crews and emergency responders in the event of an accident. The final layer of protection is typically a large containment building designed to prevent the release of nuclear material in the event that all active systems should be rendered inoperative.
Finally, beyond just technological means, human factors must also be taken into account. Elimination of conflict of interest is a key concern in regulatory strategy, and development of a safety culture to ensure that operator error does not allow avoidable errors to occur.
Nuclear power plants are one of the most sophisticated and complex energy systems ever designed, and critics have seen nuclear power as a dangerous, expensive way to boil water to generate electricity. Proponents have argued that much of that complexity is due to redundancy of systems, extensive backups, and the defence in depth strategy of design. A fundamental issue related to complexity is that the nuclear power systems have an exceedingly long stay time. The timeframe involved from the start of construction of a commercial nuclear power station, through to the safe disposal of its last radioactive waste, may be 100-150 years. There are concerns that a combination of human and mechanical error at a nuclear facility could result significant harm to people and the environment.
Operating nuclear reactors contain large amounts of radioactive fission products which, if dispersed, could pose a direct radiation hazard, contaminate soil and vegetation, and be ingested by humans and animals. Human exposure at high enough levels can cause both short-term illness and death, and longer-term deaths by cancer and other diseases.
Nuclear reactors can fail in a variety of ways. Should the instability of the nuclear material generate unexpected behaviour, it may result in an uncontrolled power excursion. Normally, the cooling system in a reactor is designed to be able to handle the excess heat this causes, however, should the reactor also experience a loss-of- coolant accident, then the fuel may melt, or cause the vessel it is contained in to overheat and melt. This event is called a nuclear meltdown. Because the heat generated can be tremendous, immense pressure can build up in the reactor vessel, resulting in a steam explosion such as happened at Chernobyl.
Two Major Accidents: The Chernobyl disaster was a nuclear reactor accident in the Chernobyl Nuclear Power Plant in the Soviet Union. It was the worst nuclear power plant disaster ever and the only level 7 instance on the International Nuclear Event Scale. It resulted in a severe release of radioactivity into the environment following a massive power excursion which destroyed the reactor.
The Three Mile Island accident of 1979 was a partial core meltdown in Unit 2 (a pressurized water reactor) of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg. It was the most significant accident in the history of the American commercial nuclear power generating industry.
The Atomic Energy Regulatory Board (AERB) was constituted in the year 1983, to perform certain regulatory and safety functions. The main mission of AREB is to ensure that the use of ionizing radiation and nuclear energy in India does not cause undue risk to health and the environment.
Convention on Nuclear Safety (CNS) is an international incentive convention aimed at maintaining high levels of safety in nuclear power plants worldwide through a system of peer reviews conducted once in three years. India ratified the convention in March 2005 making itself as a Contracting Party (CP) to CNS.
India Sets Up Nuclear Safety Research Body : India became the only country, after France, to set up a nuclear safety research institute under an independent body, with the inauguration of the Safety Research Institute at the Indira Gandhi Centre for Atomic Research at Kalpakkam, near Madras.
The SRI, slated to function under the auspices of the Atomic Energy Regulatory Board, is an essential part of the country’s nuclear research programme.
SRI would conduct research on safety aspects of nuclear facilities at design and operation stages and assess and monitor their environmental impact, apart from evolving a data base on safety codes and standards. Projects were underway with several institutions including Indian Institutes of Technology at Madras and Bombay.
NUCLEAR SAFETY ISSUES
Recent accidents, fear of radiation hazards, waste disposal etc. have created much apprehensions about the danger inherent in nuclear plants. Consideration of safety and environmental factors are of utmost importance in construction and operation of nuclear plants.
Radiation Hazards: Protection of people and | the environment from the potential hazards of 1 radiation has always been given the top priority by the nuclear plant industry. Effort has been to keep individual exposure “As low as Reasonably Achievable” (ALARA) and below the dose limit recommended by International Commission on Radiological Protection (ICRP)
Radioactive radiations, specifically gamma rays, are deeply penetrating causing ionisation of atoms in their path and hence are extremely harmful to human beings and other living organisms even in relatively small doses. The common biological effects of radiations are: (i) Carcinogenic-may cause various forms of cancer; (ii) Mutagenic-may cause a change in genetic structure (mutation) that can be inherited; and (iii) Teratogenic-may cause defect in embryo development and hence birth defects.
Nuclear Waste Management: Nuclear waste is any waste material that contains radioactive nuclei. Such materials occur in the mining of radioactive ores, generation of electricity by nuclear power, in hospitals, and in research laboratories. Nuclear waste can be extremely dangerous and the way in which they are disposed of is strictly controlled by international agreement.
After processing to recover usable material and reducing the radioactivity of the waste, disposal is made in solid form where possible. Nuclear waste may be of high level (HLW), medium level (MLW) or low level (LLW). HLW (e.g. spent nuclear fuel) has to be cooled and is therefore stored for several decades by its producer before disposal. MLW (e.g. filters, reactor components etc) is solidified and is mixed with concrete in steel drums before being buried in deep mines or below the sea bed in concrete chambers. LLW (e.g. solids or liquids contaminated with traces of radioactivity) is disposed of in steel drums in concrete-lined trenches in designated sites. Since 1983, by international agreement, disposal in the Atlantic and into the atmosphere have been banned.
In India, a Waste Immobilisation Plant (WIP) was commissioned in 1985 at Tarapore. It verifies HLW.
Safety Measures: Following safety measures are undertaken during construction, operation and decommissioning of nuclear plants.
Site selection: To study prospective sites in a given region the DAE appoints a “site selection committee” with experts from Central Electricity Authority, Atomic Minerals Division, Health and
Safety Group and the Reactor Safety Review Group of BARC and NPC. The recommendations are forwarded to DAE and AEC (Atomic Energy Commission). The final selection is made by Central Government.
Construction and Commissioning: Before construction, a licence from the Atomic Energy Regulatory Board (AERB) is required. The commissioning process includes testing and operational testing-individually and the entire system-of various systems. AERB’s stage wise clearance is mandatory before filling heavy water, loading fuel, making the reactor critical, raising steam, synchronising and reaching levels of 25%, 50%, 75% and 100% power.
Operation: During operation of nuclear power plant steps are taken to ensure prevention of leakage of radioactivity and to ensure minimum exposure of personnel. For this, continuous cooling of reactor fuel and maintenance of integrity of multiple physical barriers around the reactor is ensured in keeping with technical specification issued by AERB.
Decommissioning: A nuclear reactor has a life of30-40 years after which it has to be permanently retired; 85% of the plant never becomes radioactive and can be demolished or reused without restriction. In the remaining 15%, after the spent fuel is taken out and shifted offsite disposal, only the reactor vessel and piping are of main concern.
Decommissioning is a 37 year long process and has three stages. In the first stage, which takes about two years, all irradiated fuel, fuel coolant and other easily accessible radioactive material leaving the reactor vessel, structure and ventilation system is removed intact inside the containment building. In the second stage, the radioactive reactor vessel and components are sealed off for a dormant period of decay lasting 30 years while nonactive areas are released for other uses. In the third stage, which takes about five years, the major work of dismantling reactor vessel and piping is done with specialised remote handling techniques. The debris is then taken away, for permanent storage in steel-line repositories, in location duly approved by the AERB. The remaining areas of the plant are released for unrestricted occupancy. TAPS will be the first plant ready for decommissioning by 2005AD. The RAPS will follow in 2010 AD and MAPS in 2020 AD.
Nuclear Supplier Group (NSG)
It is a cartel that was established at the initiative of USA. At present 45 countries are the members of NSG. India, Pakistan and Israel are the notable non members of the NSG.
The NSG guidelines prohibits its members countries from transferring nuclear technology, material, fuel and components to any country that has not become a members of nuclear Non Proliferation Treaty (NPT) or has refused to accept the full scope inspection of its nuclear facilities by IAEA.. Thus the NSG has imposed nuclear technological sanctions on India. It is believed that NSG is primarily targeted against India. India in the interest of its national security had rejected the NSG’s demanding for accepting full scope inspection of its Nuclear facility but is prepared to accept reactor specific inspection by IAEA.
The indo-US nuclear deal concluded in July 15, 2205 had the potential to modify the guidelines of NSG and finally in August 2008 it allow. India to receive international assistance for establishing nuclear civilian facilities under the supervision of IAEA.
Russian Reactors (Nuclear)
In 1993 India and Russia signed an agreement under which Russia agreed to established to LWR each f 1000Mw capacity at Kudankulom in T.N .Russia would supply low enriched uranium as a fuel and heavy water as moderator for operating the nuclear reactor. In December 2001 India and Russia singed another agreement under which the cost of the reactors was fixed $2 billion of which 54% would be extended as loan by Russia to India a with an annual interest rate of 4%. The principle of the interest would be repaid India in 14 equal instalments starting from one year after the commissioning of reactors. Russia will supply the design and 90% of the components of the reactor. It will also supply low enriched uranium and heavy water for 60 years which is envisaged as the life of the reactors.
The construction of the two reactors started from March .2002. The first reactor is expected to be commissioned by 2007 and the second by 2008. The reactors would be commissioned by Russia on a Turnkey bases.
India has been requesting Russia to construct two more similar reactor at Kodonkulam but Russia had expressed its inability sighting the NSG guidelines.
It is situated at Vienna, Austria .It is one of the related agency of U.N. and it was established in 1957. Its objectives are-
- To assists the member Countries in harnessing the peaceful uses of nuclear energy.
- To provide pre scientific review of design of nuclear reactor that are placed for its inspections.
- To carry out inspection of the nuclear facility of the non nuclear weapon state that are members of N.P.T. to ensure that no nuclear material is diverted for weapons purposes. It also carries out inspection of the nuclear facilities of countries that are not members of NPT but have been placed under its control.
The IAEA has been functioning among other thing as an instrument of nuclear on proliferation. India has voluntarily placed the design of 500Mw. Proto Type F.B.R. for the peer review of IAEA which the IAEA has certifies as safe.
In 1993 the IAEA formulated “additional protocol” to prevent the emergence of W.M.D. Under this scheme the IAEA will have the right to carry out unannounced inspection of the nuclear facilities that are replaced under its control. India was pressurized to exceed to the protocol of IAEA but India refused to sign additional protocol.
It stands for World Association of Nuclear Operator. It is a non- government nuclear organization established after Chernobyl nuclear accident in former USSR in 1986. WANO was established in 1989 with it’s headquarter at London. WANO provides peer review of nuclear reactors that are voluntarily placed for its inspection and certifies about its safety of its nuclear reactor.
India has voluntarily placed Nuclear reactor at Narora and Kakarapar for peer review of WANO. At present 33 countries including India are members of WANO