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Immobilization of Concentrated Radioactive Waste from Bushehr Nuclear Power Plant in Glass Matrix

Khatirian, Mahdi | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56134 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Samadfam, Mohammad; Sepehrian, Hamid; Yadollahi, Ali
  7. Abstract:
  8. Considering the operation of the current nuclear reactors and the country's policy to achieve 10,000 megawatts of nuclear power in the horizon of 1420, in the coming years we will face a huge amount of radioactive waste, the majority of which is waste with low and intermediate levels of radioactivity (LILW). A large percentage of the radioactive waste production in Bushehr power plant is concentrated waste with a low and intermediate level of radioactivity (about 70% by volume). Due to the commisining of phase 2 and 3 of Bushehr power plant in the coming years and the increase in the radioactive waste production, proper planning should be done for waste management in order to reduce the final amount of wasteform. The process of immobilizing radioactive waste in the glass matrix is a globally accepted method for managing radioactive waste. Vitrification is attractive due to the small volume of the resulting waste form, the large number of elements that can be accommodated in the free structure of the glass, and the potentially high stability of the glasses. The high chemical resistance of glass allows it to remain stable in corrosive environments for thousands and even millions of years. In this project, the immobilization of the low and intermediate level concentrated waste produced in Bushehr power plant in the glass matrix using zeolite glass-making precursor was investigated. For this purpose, using the combined design of experiment method, the effect of the parameters of loading amount of simulated waste (30-50 Wt%), clinoptilolite zeolite (50-70 Wt%) and the melting temperature (1050-1250 °C) were investigated. Characterization of the prepared waste forms was done by XRD, SEM and EDX analyses. The chemical stability of glass wasteforms was also evaluated by standard PCT leaching test method for cesium and strontium elements. The investigations showed that the samples prepared at a temperature lower than 1150 °C with a waste loading of less than 45 Wt%, do not have an amorphous structure and have a crystalline phase, and are not chemically and structurally homogeneous. Also, in the samples with high waste loading (50 Wt% waste) at temperatures of 1150 and 1200 °C, the phase separation (white color phase containing insoluble sulfate) is clearly visible in the glass. The density of all the prepared wasteforms was measured in the range of 2.459-2.558 g/cm3 and the relative volume reduction ratio of the waste forms was found in the range of 66.8-81.3%. Based on the obtained results, with the increase in temperature and waste loading, the density and volume reduction ratio of wasteforms are increased. Investigations showed that the glass composition containing 45 Wt% waste and 55 Wt% zeolite prepared at 1150 °C provides the best conditions for waste immobilization and the normalized leaching rate of cesium and strontium elements was fouond about 0/844 and 0/8981 g/cm2.day, respectively. Also, the density and the relative volume reduction ratio of the sample preapered in optimal conditions were calculated as 2.55 g/cm3 and 78.82%, respectively
  9. Keywords:
  10. Radioactive Waste ; Strontium ; Immobilization in Glass ; Bushehr Nuclear Power Plant ; Intermediate Level Nuclear Waste (ILW) ; Low Level Nuclear Waste (LLW) ; Cesium Sorption ; Leaching

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