Simulated studies on optimization and characterization of feed and product of melter for safe disposal of high-level radioactive liquid waste. (January 2020)

• Record Type: Journal Article
• Authors: Selvakumar, J.; Rajasekaran, S.; Chitra, S.; Paul, Biplob
• Is Part Of: Progress in nuclear energy. Volume 118(2020)
• Publication Date: 2020-01
• Subjects: Vitrification -- High-level liquid waste -- Borosilicate glass -- Leaching -- Thermal study; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 333.7924
• DOI: 10.1016/j.pnucene.2019.103135
• Languages: English
• ISSNs: 0149-1970

Abstract

Abstract: 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 ·Na2 O·B2 O3 ·TiO2 ·Fe2 O3 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 × 10 −6 g/cm 2 day), generation of <0.5% respirable fines (<15 μm) 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. Highlights: First & detailed investigation of HLW vitrification at WIP, Kalpakkam, India. The reaction mechanism for the formation of the VWP visualized. The activation energy for feed to product established. Product suitability for safe interim storage and final disposal established.