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Fission Product Treatment Options
Common methods used for the removal of Sr-90, Cs-137 and Co-60 from storage pool water are ex situ removal technologies, which include; adsorption on zeolites and synthetic organic ion exchangers (Ebner et al., 2001; Paterson-Beedle et al., 2006; Smiciklas et al., 2006). However, the main disadvantages with the above methods is their unsuitability at high pH, high sodium concentrations, and in irradiated environments (Chaalal and Islam, 2001). The efficient removal and recovery of other fission products, particularly radioiodine, technetium, using physical and chemical methods are somewhat more difficult, and are still under development. In Japan, the use of inorganic sorbents for fission product removal is under investigation, while the use of extractants such as crown ethers, cobalt dicarbollides and calix-crown ethers have also been studied with some success in the United States of America, Czech Republic and France, respectively.
Apart from the high costs involved, physical and chemical methods are well known to be aggressive and invasive treatment strategies that can have negative impacts on biodiversity and can even result in increased dispersion of radioactive materials (Bazansak et al., 1999; Lloyd and Renshaw, 2005). Given the technical limitations of physico-chemical approaches, there has been an unprecedented attention on the application of innovative techniques for fission products waste treatment. Among the most successful and widely used innovative technologies for cleanup of sites contaminated with hazardous chemicals is bioremediation (the use of microorganisms or microbial processes to treat environmental metal/radionuclide contamination) (Kumar et al., 2007). Bioremediation exploits the metabolic reactions of microorganisms to destroy contaminants or to transform them into species whose mobility is controlled (Banazsak et al 1999). Bioremediation is relatively cost effective, as target compounds are stabilized and/or detoxified by the biomass, eliminating the need for expensive chemical additions to achieve the desired treatment goals (Mulligan et al., 2001). Given the potential environmental and financial benefits of bioremediation, the microbial immobilization of long-lived fission products under geologic repository settings, surprisingly, has received less attention.
The main treatment goals for nuclear wastes by biological approaches include, for example, the selective accumulation of radionuclides for possible recovery or ultimate disposal, the immobilization of radionuclides in a subsurface aquifer to prevent migration into water supplies, or the selective leaching of radionuclides from contaminated soil (Lloyd and Lovley, 2001). Ideally subsurface bioremediation strategies should require less or no maintenance; and for this reason there has been a widespread investigation of passive biological remediation techniques (Hedin et al., 1994; Younger et al., 2002). On the other hand, active in situ bioremediation treatment depends on the viability and activity of the microorganisms, which might not always be the case under high metal and radioactive stress conditions. Active bioremediation treatment requires regular monitoring of the inhabiting microbial communities. Nonetheless, both techniques rely on microbial processes that effect the retardation of fission products mobility in subsurface environments, through bioprecipitation, bioaccumulation, biosorption, and biotransformation (Lloyd and Macaskie 2000; Lloyd et al., 2002; Lloyd and Renshaw, 2005).
1 INTRODUCTION
1.1 Introduction
1.2 Aim and Objective
1.3 Scope of the Stud
1.4 Methodology
1.5 Significance of the Study
2 LITERATURE REVIEW
2.1 BACKGROUND
2.2 SPENT NUCLEAR FUEL MANAGEMENT
2.3 ENVIRONMENTAL FISSION PRODUCT CONTAMINATION
2.4 METAL IONS UPTAKE BY BACTERIA.
2.6 THE APPLICATION OF MICROBIAL TECHNOLOGY IN NUCLEAR WASTE
MANAGEMENT
3 MATERIALS AND METHODS
3.1 CHEMICALS AND REAGENTS
3.2 MICROORGANISM
3.3 MEDIA
3.4 BATCH SRB BIOREACTOR EXPERIMENTS
3.5 KINETICS OF Sr2+, Co2+ AND Cs+ BIOSORPTION FROM AQUEOUS
SOLUTION.
3.6 MAXIMUM BIOSORPTION CAPACITY OF Sr2+, Co2+ AND Cs+.
3.7 ADSORPTION OF PROTONS AND Sr2+, Co2+ and Cs+ ONTO SRB CELLS
3.8 ANALYTICAL PROCEDURES
4 Sr2+, Co2+ AND Cs+ REMOVAL IN A BATCH SULPHIDOGENIC BOREACTOR
4.1 PROSPECTS OF RADIONUCLIDE REMEDIATION IN AN SRB BIOREACTOR.
4.2 SRB CHARACTERISATION AND SCREENING
4.3 SIMULATION OF SULPHIDOGENIC BIOREACTOR PROCESSES
4.4 SUMMARY
5 KINETIC AND EQUILIBRIUM STUDIES FOR Sr2+, Co2+ AND Cs+ UPTAKE ONTO BACTERIAL CELLS
5.1 BACKGROUND
5.2 KINETIC STUDIES OF Sr2+, Co2+ and Cs+ BIOSORPTION
5.3 EQUILIBRIUM SR2+, CO2+ AND CS+ BIOSORPTION
6 CONCLUSIONS AND RECOMMENDATIONS
BIBLIOGRAPHY
APPENDICES
