Simulated studies on optimization and characterization of feed and product of melter for safe disposal of high-level radioactive liquid waste

摘要

The elemental composition of actual High-level Liquid Waste (HLW) received from reprocessing plant was estimated from analysis of several samples by using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Based on the composition, the simulated waste (20-30 wt % based on oxide content) was prepared and vitrified in SiO2 center dot Na2O center dot B2O3 center dot TiO2 center dot Fe2O3 glass system. Simulated Vitrified Waste Products (SVWPs) were characterized for their structural changes and relative thermal properties by using Infra-red (IR) spectrometry, X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) techniques. The measure of BO3, BO4, and Si-O-Si functional groups were found to be decisive in thermal and chemical durability of the products. Leach rate (LRNa) was found to be 10(-5) - 10(-6) g/cm(2) day for <= 26% waste oxide (WO) loaded SVWPs. The relative increase in surface area by imparting 1 J of energy to the SVWPs was found to be < 1.4. For the optimized feed composition (24% waste oxide), the required activation energy (E-a) for feed to glass conversion (50-200 kJ/mol) was estimated by DSC based advanced isoconversional method. Excellent surface and elemental homogeneity, internationally acceptable chemical durability (IAEA 28 days test) based on Na+ leach rate (3.5 x 10(-6) g/cm(2) day), generation of < 0.5% respirable fines ( < 15 mu m) during impact studies, of the SVWP from Joule Heated Ceramic Melter (JHCM) reveals that the optimized composition and its products are well qualified for safe operation, transit, and disposal.