Abstract
This study investigated a two-step thermochemical treatment process consisting of carbonization and halogenation for the removal of radionuclides from spent cation-exchange resin (CER). Based on a thermal analysis of cation-exchange resins, we propose a two-step thermochemical treatment process involving the conversion of spent CER into pyrocarbon and then the removal of radioactive elements from the carbonized CER by converting them volatile halides at very high temperatures. The proposed process mainly consists of a carbonization and halogenation reactor, a UHC (unburned hydrocarbon) combustor, and wet scrubber. A step-by-step experimental and numerical optimization study was conducted with the carbonization and halogenation reactor and the UHC combustor. The optimum operating conditions could be established based on the results of a thermal analysis of the CER, a nonisothermal kinetic analysis, a numerical modeling study of a plug flow reactor (PFR)-type combustor, and a thermodynamic equilibrium analysis of a system consisting of a mix of carbonized CER and halogenation gas. The results of this study present detailed design of a novel multifunctional reactor and operating conditions of a bench-scale carbonization and halogenation process. Basic performance tests using CER doped with nonradioactive Co and Cs, indicated as Cs-137/134 and Co-60/58, were conducted under the optimized conditions. The results of these tests showed that the novel thermochemical process proposed in this study is a viable process that effectively removes radioactive elements from spent CER.
Highlights
Introduction nal affiliationsIon-exchange (IE) polymer is an insoluble solid resin that acts as a medium for the ion exchange process
An optimized carbonization condition is the slow heating of the spent cation-exchange resin (CER) to 800 ◦ C from 300 ◦ C at a heating rate of 10 K/min to avoid the sudden generation of a large amount of unburned hydrocarbon (UHC), and holding the temperature at 800 ◦ C
Basic performance tests using CER doped with nonradioactive Co and Cs with an initial mass content of 0.1% of each metal were conducted under the determined appropriate carbonization and halogenation treatment conditions
Summary
CERCER (cation-exchange resin) of the target waste stream in this study is spent of type the type generated in the industry. The principal applications of ion of exchange processes in generated innuclear the nuclear industry. IE resin a 1.2:1 cation-to-anion ratioratio is generally usedused in nuclear power plants. AERAER cation-to-anion is generally in nuclear power plants. Spent mixed resinresin bed bed is conventionally separated by passing spent mixed is conventionally separated by passing water up through the resin for fluidization, allowing denser. CER settle water up through the resin bedbed for fluidization, allowing thethe denser to to setfirst[11]. Co-60 is the target waste type in this study. The chemical structure of the strong and Co-60 is the target waste type in this study.
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