Stabilization/Solidification of Radioactive LiCl-KCl Waste Salt by Using SiO₂-Al₂O₃-P₂O₅(SAP) inorganic composite: Part 1. Dechlorination Behavior of LiCl-KCl and Characteristics of Consolidation

Abstract

The metal chloride wastes from a pyrochemical process to recover uranium and transuranic elements has been considered as a problematic waste difficult to apply to a conventional solidification method due to the high volatility and low compatibility with silicate glass. In this study, a dechlorination approach to treat LiCl-KCl waste for final disposal was adapted. In this study, a SiO 2 -Al 2 O 3 -P 2 O 5 (SAP) inorganic composite as a dechlorination agent was prepared by a conventional sol-gel process. By using a series of SAPs, the dechlorination behavior and consolidation of reaction products were investigated. Different from LiCl waste, the dechlorination reaction occurred mainly at two temperature ranges. The thermogravimetric test indicated that the first reaction range was about 400°C for LiCl and the second was about 700°C for KCl. The SAP 1071 (Si/Al/P=1/0.75/1 in molar) was found to be the most favorable SAP as a dechlorination agent under given conditions. The consolidation test revealed that the bulk shape and the densification of consolidated forms depended on the SAP/Salt ratios. The leaching test by PCT-A method was performed to evaluate the durability of consolidated forms. This study provided the basic information on the dechlorination approach. Based on the experimental results, the dechlorination method using a SiO 2 -Al 2 O 3 -P 2 O 5 (SAP) could be considered as one of alternatives for the immobilization of waste salt.

Inorganic Waste Forms for Efficient Immobilization of Radionuclides

“…Sodalite is a natural aluminosilicate containing iodine/chlorine, hydroxide, and other anions in its composition and is a well-known efficient feldspathoidal mineral for the immobilization of chloride- and iodide-containing wastes (Figure B). , Various synthesis conditions were optimized for the development of sodalite-based matrices, e.g., the application of sodium aluminate and silica precursors using kaolinite, nepheline, or zeolite A (LTA). In South Korea, the Korea Atomic Energy Research Institute (KAERI) also developed SAP as an efficient immobilization matrix for chloride-containing wastes. , The authors proposed that the SAP can be synthesized by the sol–gel method, and it is highly capable of capturing and stabilizing volatile salt wastes in the form of metal aluminosilicates, aluminophosphates, and phosphates . Moreover, the design and synthesis of glassy waste form (U-SAP) was developed as an alternative matrix for other SAP waste forms …”

An experimental study on Sodalite and SAP matrices for immobilization of spent chloride salt waste

“…The Korea Atomic Energy Research Institute (KAERI) proposed an immobilization matrix for chloride salt wastes, termed SAP, consisting of SiO 2 ,Al 2 O 3 and P 2 O 5 [27,28]. This matrix, synthesized by a conventional sol-gel process, is able to stabilize volatile salt wastes due to the formation of metal aluminosilicates, aluminophosphates and phosphates, generating chlorine gas [29].…”