Myung-Jae Song

Vitrification of liquid waste from nuclear power plants

Abstract Glass is an acceptable waste form to solidify the low-level waste from nuclear power plants (NPPs) because of the simplicity of processing and its unique ability to accept a wide variety of waste streams. Vitrification is being considered to solidify the high-boron-containing liquid waste generated from Korean NPPs. This study dealt with the development of a glass formulation to solidify the liquid waste. Studies were conducted in a borosilicate glass system. Crucible studies have been performed with surrogate waste. Several developed glass frits were evaluated to determine their suitability for vitrifying the liquid waste. The results indicated that the 20 wt% waste oxides loading required could not be obtained using these glass frits. Flyash produced from coal-burning electric power stations, whose major components are SiO 2 and Al 2 O 3 , is a desirable glass network former. Detailed product evaluations including waste loading, homogeneity, chemical durability and viscosity, etc., were carried out on selected formulations using flyash. Up to 30 wt% of the waste oxides was successfully solidified into the flyash after the addition of 5–10 wt% Na 2 O at 1200°C.

Utilizing the KEP-A glass frit to vitrify low-level radioactive waste from Korean NPPs

Abstract Vitrification has been considered as an integrated, cost effective, and environmentally sound solution for low-level radioactive waste (LLW) generated from nuclear power plants (NPPs) in Korea. Korea is in the process of preparing for its first ever vitrification plant to handle LLW from her NPPs. As a part of this project, Nuclear Environment Technology Institute (NETEC) is developing glass formulae for the different waste streams. KEP-A is the glass frit which has been developed to vitrify polyvinyl chloride (PVC) from Korean NPPs. Since 1996, glass formulae have been studied in lab-scale using simulated wastes by considering leacheability of the waste glass and viscosity of the glass melt. Based on the database of 55 glasses, on the ternary diagram of Si/Al-B/alkali–other components, the acceptance regions of the waste glasses have been presented considering its durability and viscosity. Utilizing one glass frit to vitrify different waste types with variable compositions is a sub-topic of this project. This paper presents the test results of glass formulation to vitrify other low-level radioactive waste from Korean NPPs. The waste streams include three categories, combustible Dry Active Wastes (DAW), borate waste, and spent resin. The combustible DAW in this research contain PVC, paper, and cotton. Considering chemical durability and viscosity, it is found that the KEP-A glass frit can be used to vitrify mixtures of combustible DAW up to 50 wt% of ash loading. The KEP-A allows wide composition range of combustible DAW while maintaining good durability. However, with more than 15 wt% of ash loading of borate waste or spent resin, the KEP-A could not produce a durable glass.

Vitrification of Polyvinyl Chloride Waste from Korean Nuclear Power Plants

Abstract Vitrification is considered as an economical and safe treatment technology for low-level radioactive waste (LLW) generated from nuclear power plants (NPPs). Korea is in the process of preparing for its first ever vitrification plant to handle LLW from its NPPs. Polyvinyl chloride (PVC) has the largest volume of dry active wastes and is the main waste stream to treat. Glass formulation development for PVC waste is the focus of study. The minimum additive waste stabilization approach has been utilized in vitrification. It was found that glasses can incorporate a high content of PVC ash (up to 50 wt%), which results in a large volume reduction. A glass frit, KEP-A, was developed to vitrify PVC waste after the optimization of waste loading, melt viscosity, melting temperature, and chemical durability. The KEP-A could satisfactorily vitrify PVC with a waste loading of 30 to 50 wt%. The PVC-frit was tolerant of variations in waste composition.

Glass Formulations for Vitrification of Low-and Intermediate-level Waste

In order to develop glass formulations for vitrifying Low-and Intermediate-Level radioactive Wastes (LILW) from nuclear power plants of Korea Hydro & Nuclear Power (KHNP) Co., Ltd., promising glass formulations were selected based on glass property model predictions for viscosity, electrical conductivity and leach resistance. Laboratory measurements were conducted to verify the model predictions. Based on the results, the models for electrical conductivity, US DOE 7-day Product Consistency Test (PCT) elemental release, and pH of PCT leachate are accurate for the LILW glass formulations. However, the model for viscosity was able to provide only qualitative results. A leachate conductivity test was conducted on several samples to estimate glass leach resistance. Test results from the leachate conductivity test were useful for comparison before PCT elemental release results were available. A glass formulation K11A meets all the KHNP glass property constraints, and use of this glass formulation on the pilot scale is recommended. Glass formulations K12A, K12B, and K12E meet nearly all of the processing constraints and may be suitable for additional testing. Based on the comparison between the measured and predicted glass properties, existing glass property models may be used to assist with the LILW glass formulation development.