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Atmospheric testing of nuclear weapons and nuclear reactor accidents has resulted in widespread distribution of radioactive fission products into the environment. Determination of these radionuclides in biological and environmental samples presents serious difficulties because of interferences (90Sr with a continuous beta spectrum needs separation from other radionuclides, such as 90Y) and the poor limits of detection established by currently available counting equipment. In this project an ion exchange chromatography procedure for the separation of Cs, Sr and Y was developed. Since these radionuclides are hazardous, the method was developed using stable isotopes and inductively coupled plasma mass spectrometry (ICP-MS) as an elemental detector. In the first instance, the optimum operating conditions of the instrument for the analysis of Cs, Sr and Y were determined. These values were found to be 1.1 kW incident power and 1 1 min-1 nebuliser flow rate. The accuracy of the ICP-MS measurments was then assessed through the use of international reference materials NIST:SRM 1572 Citrus Leaves and NIST:SRM 1573 Tomato Leaves. In general a good agreement was observed for most of the elements between certified values and the results obtained in this study. The developed separation technique consisted of three stages. In the first stage ammonium molybdophosphate (AMP) and BioRad AG 50W-X8 resins were used. Caesium was separated from the other two isotopes using 2 M NH4OH. In the second stage Sr and Y were eluted from the above mentioned column using 4 M HNO3. The solution was then loaded onto a Sr-SpecRTM column where Sr is retained. In the third stage Sr was eluted from the column using deionised water. This setup provided excellent recoveries for the three stages namely: 85 % for Cs, 93 % for Y and 95 % for Sr. The analysis of Cs, Sr, and Y in foodstuffs, namely beans and milk was carried out after using the aforementioned separation procedure. Different growth media (commercial white silica sand, Lightwater garden soil, commercial garden soil, Rose Batch compost, and commercial compost) were used to assess the effect of organic content on the uptake of Cs and Sr by bean plants. These experiments involved the addition of different doses of added elemental concentration (100 to 1000 ?g ml-1) to the substrate and also various solution pH's (4 to 9). It was observed that the higher uptake of Cs and Sr by bean plants was at solution pH 7 and also for growth media with high organic content, i.e. Rose Batch compost and commercial compost. The distribution of Cs and Sr into the bean plant tissue resulting through absorption from commercial compost, showed that Cs is absorbed mostly in the stem (95 %) and with minimal levels in root and leaves (5 %). On the other hand, Sr was readily absorbed to the aboveground parts of the bean plants (36 % stem, 63 % in leaves) in contrast to other parts; 0.3 % root and 0.05 % beans. A study was undertaken to assess the uptake of Cs and Sr by bean plants in the presence of K and Ca at various solution pH's. It was found that in general, for all solution pH's, potassium inhibits the uptake of Cs. On the other hand, there appears to be a competition between Sr and Ca at high pH (7 to 9) which resulted in a rapid reduction of the Sr uptake. The addition of Ca to the substrate decreased the uptake of Sr by stems/leaves and increased the uptake of Sr by beans. As an application, solutions with different pH and radionuclide 137Cs and 90Sr) levels were added to mature bean plants. The developed ion exchange chromatography procedure was then adopted to separate 137Cs and 90Sr from these plants. In this study a Ge(Li) gamma ray spectrometer (ND 66) was used as a detector for 137Cs whilst a liquid scintillation counter was used for measuring 90Sr. Prior to the 137Cs measurements, the detection limits, resolution, absolute full energy peak and calibration of the instrument were evaluated. In general the values obtained in this work were in good agreement with the certified values.

There have been a lot of questions on impact of greenhouse gas on changes in climate conditions regarding expected future dangers if mitigation measures are not put in place. Carbon dioxide emission from power sector is a major contributor of greenhouse gases. As a result, the sector is key target for deploying carbon abatement technologies such as carbon capture. Post-combustion capture (PCC) based on chemical absorption technology is one of the major capture approaches and the most matured of them. However, it is beset by some challenges such as high capital and operating costs due to required large sizes of packed columns and high solvent re-circulating rate. Through process intensification (PI) technology, the columns could be downsized by an order of magnitude without compromising their processing capacity. However, there have been limited studies on the techno-economics of PI-based technologies. In this study, steady state models for standalone intensified absorber and stripper based on rotating packed bed (RPB) technology were developed and validated with experimental data from Newcastle University UK and Tsing Hua University Taiwan respectively. The models were developed in Aspen Plus® and dynamically linked with visual Fortran subroutines. Therefore, this is same as newly developed RPB models (i.e. absorber and stripper). To obtain more insights into the design and operation of standalone intensified absorber, standalone intensified stripper and close loop intensified PCC process, process analysis was carried out. Process analysis in standalone intensified absorber indicates that: (a) CO₂ capture level increases with increase in rotating speed. (b) Higher lean MEA inlet temperature leads to higher CO₂ capture level. (c) Increase in lean MEA concentration results in increase in CO₂ capture level. (d) Temperature bulge is not present in intensified absorber. (e) With fixed RPB equipment size and fixed Lean MEA flow rate, CO₂ capture level decreases with increase in flue gas flow rate. (f) At higher flue gas temperature (from 30°C to 80°C), the CO₂ capture level of the intensified absorber can be maintained. For standalone intensified stripper, the impact of rotor speed on the regeneration efficiency and energy were studied, the impact of reboiler temperature on the rate of CO₂ stripping was established and the impact of rich-MEA flow rate on regeneration energy and efficiency was determined. From comparative assessment of conventional packed bed and RPB, it was found that a volume reduction factor of 12 and 10 times is possible for the absorber and stripper respectively. The two validated models, together with model for heat exchanger were then linked together to form a closed loop intensified PCC process. Steady state model of the closed loop intensified PCC process was then used to perform process analysis on (i) the impact of liquid to gas (L/G) ratio on regeneration energy and CO₂ capture level, (ii) the impact of lean-MEA loading on regeneration energy and capture level (iii) capital and operating cost estimation for intensified PCC process were done, which shows a reduction in an investment cost compared to conventional PCC process. The findings in this study showed that capital and operating costs can be reduced owing to its smaller size compared to conventional PCC process. Also cooling cost for flue gas and inter-cooling in the absorber can be saved since the RPB absorber can be operated at slightly elevated temperature of up to 80°C without compromising the absorber performance and also since higher lean-MEA temperature and/or higher flue gas temperature shows little or no effect on the performance of the RPB. The newly proposed intensified PCC process PFD in the recommendation section of this thesis if successfully implemented can reduce operating and capital costs of PCC process. Finally, these insights can be useful for the design and operation of intensified PCC process.

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