Radioactive Waste Disposal - Essay Example

Word Count 1991) Introduction This paper seeks to understand the issues involved in the disposal of radioactive wastes and the policy followed by the United Kingdom in the management of radioactive waste. The discussions put forth in this paper will be supported by the information provided by several journals, websites dedicated to the subject of nuclear waste and policy documents published by Government departments. The first part of the paper will focus on what is radioactive waste, the categories, with focus of Intermediary level wastes (ILW) and High level wastes (HLW) and how these must be disposed. The second part will deal with the methods used for the management of ILW and HLW in UK. The focus will then shift to the concept of repositories and their impact in the long term. The last section will discuss how the UK is likely to resolve the issue of nuclear waste in the long term and whether that will be in line with the current thinking on that issue. The issue of radioactive waste disposal is a very serious one. Nuclear power for instance contributes to 23% of UK electricity needs.(Department for Environment, Food and Rural Affairs.2001) However its sustainability is suspect until efficient means to manage and dispose radioactive nuclear wastes is found. Stockpiles of nuclear waste are accumulating in several nations. Improper storage can cause exposure to radiation, which results in health and environmental hazards. Also these can be used as weapons of mass destruction if they are found by terrorist organizations. Hence strategies for disposal must involve a multi-dimensional approach with consideration ethical and environmental factors while taking into account the principles of inter and intra-generational equity. Radioactive Wastes Radio active or nuclear waste is the product of a nuclear process, radioactive waste consists of materials containing radioactive chemical elements. generated in the processing of fuel for nuclear reactors or nuclear weapons and in the process of nuclear fission. (Wikipedia) Radiation occurs from the decay of radioisotopes. Each of these radioisotopes in the radioactive waste has a half-life which is the time taken for half its atoms to decay. The faster a radioisotope decays, the more radioactive it is. (World Nuclear Association 2001) Fig1. Comparison in the corresponding rates of decay of uranium ore and other HLW from the reprocessing of spent fuel. Source:World Nuclear Association 2001, Radioactive Wastes. The classification of radioactive wastes and their disposal depends on how long it remains highly radioactive, the concentration of the radioactive material in the waste and whether the waste is heat generating. The persistence of the radioactivity determines how long the waste requires management. The concentration and heat generation dictate how the waste should be handled. (World Nuclear Association 2001). Radioactive wastes are generally classified into Low-level Wastes (LLW) -generated from hospitals and industry, as well as the nuclear fuel cycle, contain very small amounts of radio active substances that do not need to be shielded in the process of handling or transportation. (World Nuclear Association 2001) Intermediate-level Wastes (ILW) contain higher amounts of radioactivity and some require shielding. It comprises of resins, chemical sludges and metal fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen for disposal. Generally short lived waste from reactors is buried in shallow repositories, while long lived waste from fuel reprocessing will be disposed of deep underground (Wikipedia) High-level Wastes (HLW) result from of the use of uranium fuel in a nuclear reactor. It contains the fission products and transuranic elements generated in the reactor core. Highly radioactive and hot, HLW’s require cooling and shielding. HLW accounts for over 95% of the total radioactivity produced in the process of electricity generation. (World Nuclear Association 2004) HLW’s are of two types, the fission products and transuranics separated from the spent fuel and the spent fuel elements themselves from the reactor core when they are not reprocessed. (World Nuclear Association 2001). Both these need treatment before they can be disposed. In a process called vitrification., HLW from reprocessing is incorporated into solid blocks of borosilicate glass. For direct disposal, spent fuel requires encapsulation in containers made, of stainless steel or copper (World Nuclear Association 2001). Disposal of ILW and HLW In the United Kingdom The UK does not have a final management strategy for both ILW and HLW. (Department for Environment, Food and Rural Affairs (DEFRA) 2001) Between 1949 and 1982, 73,530 tonnes of low and intermediate waste has been disposed of by the UK to the North East Atlantic. Since then this waste, has been stocked. According to the 1998 inventory, 71,000m3 of ILW is in storage, 8,500m3 of which has been treated to for long term management. Stored in stainless steel drums of 500 litre capacity , this ILW both in raw and treated forms is then deposited in shielded building or vaults at the site where it is created, mostly at the Sellafield. Plant.(Department for Environment, Food and Rural Affairs (DEFRA) 2001). There is expected to be a marked increase in the production of ILW with the decommissioning of several nuclear reactors in the UK.Fig.2 illustrates the same. Fig:2 Increase in production of ILW. After 2020, bulk of the ILW will result from the decommissioning of nuclear reactors in the UK. Source: Department for Environment, Food and Rural Affairs (DEFRA) 2001, Managing Radioactive Waste Safely Proposals for developing a policy for managing solid radioactive waste in the UK According to the DEFRA report, in the UK, HLW have been accumulated since 1950’s at Sellafield and Dounreay as the concentrated liquid nitric acid product from the reprocessing of spent nuclear fuel. This heat generating high-level waste, has been stored in facilities that have a cooling system to dissipate the heat. Also there is massive concrete shielding to protect the operators. The Health and Safety Executive (HSE) reported in 2000 that there were 1300m3 of liquid HLW stored in water-cooled tanks at Sellafield. The equivalent of a further 900m3 of liquid HLW had already been converted at Sellafield into a solid and stable form by immobilising it in glass (vitrification) within stainless steel canisters of about 140-litre capacity. There is a smaller quantity of less active HLW, 230m3, in liquid form at Dounreay. (Department for Environment, Food and Rural Affairs (DEFRA) 2001) Fig 3: Reflects the rate of production and accumulation of HLW in UK Source: Department for Environment, Food and Rural Affairs (DEFRA) 2001, Managing Radioactive Waste SafelyProposals for developing a policy for managing solid radioactive waste in the UK Geological Disposal of Radioactive Waste A final disposal strategy is essential for all radioactive wastes. Even with implementation of systems like reprocessing of spent fuel , there is a final residue s to be disposed safely. Often these wastes can emit radiation for thousands of years and need to be isolated from the environment. The fact that such isolation is possible has been proved by nature herself. Some 2 billion years ago, at Oklo, now Gabon in West Africa, where six spontaneous nuclear reactors operated within a rich vein of uranium ore. (At that time the concentration of U-235 in all natural uranium was about 3%.) These natural nuclear reactors continued for about 500,000 years before dying away. They produced all the radionuclides found in HLW, including over 5 tonnes of fission products and 1.5 tonnes of plutonium. All this remained at the site till they decayed to become non radioactive and non hazardous. (World Nuclear Association, 2004). Extensive research and natural analogues have led experts to believe that underground repositories are the best for storage of nuclear waste. The ‘Repository concept’ says that the repositories must be deep underground with layers of soil and rock to shield all radiation. Also underground repositories must be in a relatively dry area to prevent water from coming in contact with the waste. Water over time can break it down to tiny radioactive particles and carry it to the larger environment. One such repository chosen is the Yucca Mountain site in Nevada. Packed into durable ‘waste packages’, the waste is placed in deep underground tunnels. Drip shields made of another corrosion resistant metal will be placed over the waste packages. (International Atomic Energy Association website) Fig.2 Yucca Mountain Repository Site. Source: GRB Consulting Services, Nuclear Containment & Disposal Actions for Yucca Mountain Repository Site (Note: Fig.2: The Exploratory Studies Facility (ESF) will provide scientists and engineers a platform to work off and gather information about the interior make up of the mountain to determine whether or not the mountain can serve as an underground high-level nuclear waste repository. The water table here is some 240-370 m below the proposed repository area) These natural repositories are also supported by an engineered system that provides for the physical and chemical containment of the waste. (OECD Nuclear Energy Agency 1999) Final disposal of radioactive wastes in underground geological repositories is already underway in some countries. The USA has the first purpose-built, deep geologic repository for long-lived wastes in south-eastern New Mexico. The waste to be disposed of contains significant long-lived radioactive components. The waste is placed in caverns excavated at a depth of 650 metres below ground in a bedded salt formation. (OECD Nuclear Energy Agency 1999). Used for the disposal of low and medium level wastes, such repositories are available in Sweden, Norway and Finland. At the Forsmark nuclear site in Sweden, the disposal caverns are excavated in granitic bedrock, offshore, about 60 metres below the bed of the Baltic Sea, and accessed by a tunnel from land. In Finland, the facilities at the Olkiluoto nuclear site and the Loviisa site consist of caverns excavated in granitic bedrock at depths of around 100 metres below ground. The Himdalen facility in Norway consists of four caverns under 50 metres of bedrock cover. (OECD Nuclear Energy Agency 1999). Long-term Waste disposal Strategies There is a lot of public anxiety over the safety of geological repositories. People across the world have expressed fear or disapproval over the possibility of nuclear waste being disposed in their area. Despite extensive research on the subject, such concerns cannot be ignored, as experience of operating repositories has not yet been obtained. (International Atomic Energy Agency 2003) To counter this uncertainty, the Nuclear Energy Agency (NEA) recommends the implementation of stepwise decision-making that allows for the reversibility of decisions. This may include decisions regarding site selection, design options, construction and operation. Reversal may involve modifications of some aspects of the facility or retrieval of waste packages. (Nuclear Energy Agency, Radioactive Waste Management Committee 2004)The NEA /RWD also states that stress must be given to increasing public participation in decision-making process. Measures are on in the UK to effectively evolve a policy for the final disposal of radioactive wastes. The Royal Society (Royal Society Policy Document 2002) recognizes that there is an urgent need to reconsider the waste management policy n the UK. Public participation and the involvement of the international community especially the European Union has been stressed upon. Factors like terrorism are also to be considered seriously. Conclusion It is likely that UK will opt for underground storage of their radioactive wastes. The DEFRA document discusses some of the other options that have been considered for waste disposal and why they are unsuitable. The surface level repositories in which UK stores its ILW and HLW may be considered as a long-term option but there is constant threat of human intervention, which can be risky. Also designing structures and packaging of these wastes could be difficult as a significant portion of the wastes could emit radiation for over 10,000 years. Other options include disposal at sea and in empty offshore oil and gas fields. However these been ruled out under the 1997 London Convention and Convention for the Protection of the North-East Atlantic (OSPAR). This agreement calls for UK to stop sea dumping and using sea beds for storing wastes. Disposal in outer space has also been ruled out as a large number of rocket launches would be required and the potential dangers of a launch failure. Two other options that have been considered are the subduction zones and ice sheets. Subduction zones are areas where a geological plate is driven towards the earth’s core by collision with another plate and ice-sheets are the polar ice caps under which the wastes may be disposed. However both these are not considered suitable as there is uncertainty about the fate of these wastes in the long term. .( Department for Environment, Food and Rural Affairs (DEFRA) 2001 ) The UK CEED Consensus Conference on Radioactive Waste Management also recommended that Radioactive waste must be removed from the surface and stored underground, but must be monitorable and retrievable.( Department for Environment, Food and Rural Affairs (DEFRA) 2001 ) While ensuring that the nuclear waste is safely stored underground yet, retrievable and monitorable, UK is also likely to follow the NEA recommendation of stepwise wise and reversible decision-making. This will result in a vibrant open-ended strategy that will help UK cope with the changes in technological progress, public sentiment, and learn from the experiences of other repositories. References: Cohen, B.L (1990) The Nuclear Energy Option,(online version), http://www.phyast.pitt.edu/~blc/book/chapter11.html Accessed on 11th November, 2005. Department for Environment, Food and Rural Affairs, Department of the Environment, National Assembly for Wales, Scottish Executive (2001), Managing Radioactive Waste Safely Proposals for developing a policy for managing solid radioactive waste in the UK, www.defra.gov.uk/environment/ consult/radwaste/pdf/radwaste.pdf Accessed on 11th November 2005. GRB Consulting Services, Nuclear Containment & Disposal Actions for Yucca Mountain Repository Site, http://home.mho.net/novkovic/grb/env/yucca/yuccamtn.html#Repository%20Design Accessed on 11th November 2005. 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