This paper presents a study on the process engineering aspects of relevance to the industrial implementation of ThO2 and (Th, U)O2 mixed oxide (MOX) pellet type fuel manufacturing. The paper in particular focuses on t...This paper presents a study on the process engineering aspects of relevance to the industrial implementation of ThO2 and (Th, U)O2 mixed oxide (MOX) pellet type fuel manufacturing. The paper in particular focuses on the recycling of thoria based fuel production scrap which is an economically important component in the fuel manufacturing process. The thoria based fuels are envisaged for Advanced Heavy Water Reactor (AHWR) and other reactors important to the Indian Nuclear Power Programme. A process was developed for recycling the chemically clean, off-specification and defective sintered ThO2 and (Th, U)O2 MOX nuclear fuel pellets. ThO2 doesn’t undergo oxidation or reduction and thus, more traditional methods of recycling are impractical. The integrated process was developed by combining three basic approaches of recycling namely mechanical micronisation, air oxidation (for MOX) and microwave dissolution-denitration. A thorough investigation of the influence of several variables as heating method, UO2 content, fluoride and polyvinyl alcohol (PVA) addition during microwave dissolution-denitration was recorded on the product characteristics. The suitability evaluation of the recycled powder for re-fabrication of the fuel was carried out by analyzing the particle size, BET specific surface area, phase using XRD, bulk density and impurities. The physical and chemical properties of recycled powder obtained from the sintered (Th1-y, Uy)O2 (y;0 - 30 wt%) pellets advocate 100% utilisation for fuel re-fabrication. Recycled ThO2 by integrated process showed distinctly high sinterability compared to standard powder evaluated in terms of surface area and particle size.展开更多
研究烧结温度和Th含量对(Th,U)O2芯块密度的影响,计算不同Th含量的(Th,U)O2芯块烧结活化能,通过扫描电镜(SEM)分析(Th,U)O2芯块中气孔的变化迁移过程。结果表明:在相同烧结温度下,(Th,U)O2芯块密度随Th含量的增大而降低;随烧结温度升高...研究烧结温度和Th含量对(Th,U)O2芯块密度的影响,计算不同Th含量的(Th,U)O2芯块烧结活化能,通过扫描电镜(SEM)分析(Th,U)O2芯块中气孔的变化迁移过程。结果表明:在相同烧结温度下,(Th,U)O2芯块密度随Th含量的增大而降低;随烧结温度升高,芯块密度增大,在此过程中存在一个使芯块快速致密化的烧结势垒温度;(Th,U)O2芯块烧结活化能随Th含量的增大而增大,Th含量(摩尔分数)为20%、50%、80%的(Th,U)O2芯块的烧结活化能分别为277.65、300.70、380.99 k J/mol;在Th含量为20%的(Th,U)O2芯块中,气孔呈球形分布于晶界交汇处。展开更多
文摘This paper presents a study on the process engineering aspects of relevance to the industrial implementation of ThO2 and (Th, U)O2 mixed oxide (MOX) pellet type fuel manufacturing. The paper in particular focuses on the recycling of thoria based fuel production scrap which is an economically important component in the fuel manufacturing process. The thoria based fuels are envisaged for Advanced Heavy Water Reactor (AHWR) and other reactors important to the Indian Nuclear Power Programme. A process was developed for recycling the chemically clean, off-specification and defective sintered ThO2 and (Th, U)O2 MOX nuclear fuel pellets. ThO2 doesn’t undergo oxidation or reduction and thus, more traditional methods of recycling are impractical. The integrated process was developed by combining three basic approaches of recycling namely mechanical micronisation, air oxidation (for MOX) and microwave dissolution-denitration. A thorough investigation of the influence of several variables as heating method, UO2 content, fluoride and polyvinyl alcohol (PVA) addition during microwave dissolution-denitration was recorded on the product characteristics. The suitability evaluation of the recycled powder for re-fabrication of the fuel was carried out by analyzing the particle size, BET specific surface area, phase using XRD, bulk density and impurities. The physical and chemical properties of recycled powder obtained from the sintered (Th1-y, Uy)O2 (y;0 - 30 wt%) pellets advocate 100% utilisation for fuel re-fabrication. Recycled ThO2 by integrated process showed distinctly high sinterability compared to standard powder evaluated in terms of surface area and particle size.
文摘研究烧结温度和Th含量对(Th,U)O2芯块密度的影响,计算不同Th含量的(Th,U)O2芯块烧结活化能,通过扫描电镜(SEM)分析(Th,U)O2芯块中气孔的变化迁移过程。结果表明:在相同烧结温度下,(Th,U)O2芯块密度随Th含量的增大而降低;随烧结温度升高,芯块密度增大,在此过程中存在一个使芯块快速致密化的烧结势垒温度;(Th,U)O2芯块烧结活化能随Th含量的增大而增大,Th含量(摩尔分数)为20%、50%、80%的(Th,U)O2芯块的烧结活化能分别为277.65、300.70、380.99 k J/mol;在Th含量为20%的(Th,U)O2芯块中,气孔呈球形分布于晶界交汇处。
