A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was use...A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was used to calculate the size dissolution rate, dissolution time and mass of alumina dissolved employing commercial software and custom algorithm based on the shrinking sphere assumption. The effects of some convection and thermal condition parameters on the dissolution process were studied. The calculated results show that the decrease of alumina content or the increase of alumina diffusion coefficient is beneficial for the increase of size dissolution rate and the decrease of dissolution time of non-agglomerated particles. The increase of bath superheat or alumina preheating temperature results in the increase of size dissolution rate and the decrease of dissolution time of agglomerated particles. The calculated dissolution curve of alumina（mass fraction of alumina dissolved） for a 300 k A aluminum reduction cell is in well accordance with the experimental results. The analysis shows that the dissolution process of alumina can be divided into two distinct stages： the fast dissolution stage of non-agglomerated particles and the slow dissolution stage of agglomerated particles, with the dissolution time in the order of 10 and 100 s, respectively. The agglomerated particles were identified to be the most important factor limiting the dissolution process.展开更多
In this paper,the activation energy for precipi- tate dissolution in binary AI-Li alloy has been in- vestigated by considering precipitate dissolution in Al-Li alloy,continuously heated as a thermally ac- tivated proc...In this paper,the activation energy for precipi- tate dissolution in binary AI-Li alloy has been in- vestigated by considering precipitate dissolution in Al-Li alloy,continuously heated as a thermally ac- tivated process.The proposed calculation was car- ried out by changing the scanning rate in DSC measurement.The results show that the formation of GP zone is easy because the activation energy for its dissolution is smaller than that for Li atom diffu- sion in the matrix.The δ′dissolution consists of two steps:the first step needs larger thermal activation to break down the superlattice structure,and the second is much easier like GP zone dissolution.The phase is the most stable,which needs much larger thermal activation to disappear.展开更多
Radioactive iodine(such as 129I and 131I)is one of the major gaseous contaminants resulting from the utilization of nuclear energy and/or nuclear accidents.During the initial dissolution process in the spent fuel repr...Radioactive iodine(such as 129I and 131I)is one of the major gaseous contaminants resulting from the utilization of nuclear energy and/or nuclear accidents.During the initial dissolution process in the spent fuel reprocessing,for example,most of the iodine is released into the off-gas system in the form of highly volatile I2 and small amounts of organic iodine compounds(such as methyl iodide,ethyl iodide,butyl iodide).The remaining iodine in the dissolution solution exists in the forms of I2,IO3−,I−,IO−,and iodine colloids(AgI,PdI2).When the iodine in the dissolution solution enters the subsequent solvent extraction process,it can lead to solvent degradation,organic iodine formation,and reduction in the quality of uranium and plutonium products.Therefore,during the dissolution stage of spent fuel elements,it is generally preferred to convert as much iodine in the dissolution solution as possible into I2 and drive it into the off-gas.Overall,in the current nuclear fuel cycle system,radioactive iodine produced by nuclear fission mainly exists in the gaseous form.In the event of an accident,this radioactive iodine can easily leak,which presents a potential threat to the environment and public health due to its long half-life(e.g.,129I has a half-life of 1.57×10^(7)years),high mobility,ease of dispersion through air and water,and tendency to accumulate in living organisms[1].Consequently,the development of efficient and recyclable adsorbent materials for the capture and fixation of radioactive iodine has become a research priority in the fields of nuclear environmental remediation,nuclear emergency response,and nuclear fuel cycle management.Covalent organic frameworks(COFs),as a novel class of crystalline porous materials,have demonstrated promising potential for the capture of gaseous radioactive iodine due to their distinctive physicochemical properties[2,3].Specifically,COFs are composed of organic monomers connected by covalent bonds,providing high chemical and thermal stability.And the highly conjugated structure of COFs can significantly improve their resistance to irradiation[4].These enable them to maintain structural integrity and functionality under various extreme environments,making them suitable for handling complex radioactive contamination scenarios.This enables them to maintain structural integrity and functionality under various extreme environments,making them suitable for handling complex radioactive contamination scenarios.展开更多
基金Project(2010AA065201)supported by the High-tech Research and Development Program of ChinaProject(2013zzts038)supported by the Fundamental Research Funds for the Central Universities of Central South University,ChinaProject(ZB2011CBBCe1)supported by the Major Program for Aluminum Corporation of China Limited
文摘A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was used to calculate the size dissolution rate, dissolution time and mass of alumina dissolved employing commercial software and custom algorithm based on the shrinking sphere assumption. The effects of some convection and thermal condition parameters on the dissolution process were studied. The calculated results show that the decrease of alumina content or the increase of alumina diffusion coefficient is beneficial for the increase of size dissolution rate and the decrease of dissolution time of non-agglomerated particles. The increase of bath superheat or alumina preheating temperature results in the increase of size dissolution rate and the decrease of dissolution time of agglomerated particles. The calculated dissolution curve of alumina（mass fraction of alumina dissolved） for a 300 k A aluminum reduction cell is in well accordance with the experimental results. The analysis shows that the dissolution process of alumina can be divided into two distinct stages： the fast dissolution stage of non-agglomerated particles and the slow dissolution stage of agglomerated particles, with the dissolution time in the order of 10 and 100 s, respectively. The agglomerated particles were identified to be the most important factor limiting the dissolution process.
文摘In this paper,the activation energy for precipi- tate dissolution in binary AI-Li alloy has been in- vestigated by considering precipitate dissolution in Al-Li alloy,continuously heated as a thermally ac- tivated process.The proposed calculation was car- ried out by changing the scanning rate in DSC measurement.The results show that the formation of GP zone is easy because the activation energy for its dissolution is smaller than that for Li atom diffu- sion in the matrix.The δ′dissolution consists of two steps:the first step needs larger thermal activation to break down the superlattice structure,and the second is much easier like GP zone dissolution.The phase is the most stable,which needs much larger thermal activation to disappear.
基金supported by the New Iodine Adsorbent Material Project(JCKY2022130C022)the National Science Fund for Distinguished Young Scholars(21925603).
文摘Radioactive iodine(such as 129I and 131I)is one of the major gaseous contaminants resulting from the utilization of nuclear energy and/or nuclear accidents.During the initial dissolution process in the spent fuel reprocessing,for example,most of the iodine is released into the off-gas system in the form of highly volatile I2 and small amounts of organic iodine compounds(such as methyl iodide,ethyl iodide,butyl iodide).The remaining iodine in the dissolution solution exists in the forms of I2,IO3−,I−,IO−,and iodine colloids(AgI,PdI2).When the iodine in the dissolution solution enters the subsequent solvent extraction process,it can lead to solvent degradation,organic iodine formation,and reduction in the quality of uranium and plutonium products.Therefore,during the dissolution stage of spent fuel elements,it is generally preferred to convert as much iodine in the dissolution solution as possible into I2 and drive it into the off-gas.Overall,in the current nuclear fuel cycle system,radioactive iodine produced by nuclear fission mainly exists in the gaseous form.In the event of an accident,this radioactive iodine can easily leak,which presents a potential threat to the environment and public health due to its long half-life(e.g.,129I has a half-life of 1.57×10^(7)years),high mobility,ease of dispersion through air and water,and tendency to accumulate in living organisms[1].Consequently,the development of efficient and recyclable adsorbent materials for the capture and fixation of radioactive iodine has become a research priority in the fields of nuclear environmental remediation,nuclear emergency response,and nuclear fuel cycle management.Covalent organic frameworks(COFs),as a novel class of crystalline porous materials,have demonstrated promising potential for the capture of gaseous radioactive iodine due to their distinctive physicochemical properties[2,3].Specifically,COFs are composed of organic monomers connected by covalent bonds,providing high chemical and thermal stability.And the highly conjugated structure of COFs can significantly improve their resistance to irradiation[4].These enable them to maintain structural integrity and functionality under various extreme environments,making them suitable for handling complex radioactive contamination scenarios.This enables them to maintain structural integrity and functionality under various extreme environments,making them suitable for handling complex radioactive contamination scenarios.
