{"title":"Assessing ceramic powder quality by activated Sinterability Test: The case of UO2","authors":"Balakrishna Palanki","doi":"10.1016/j.jnucmat.2024.155531","DOIUrl":null,"url":null,"abstract":"<div><div>Ceramics fail by brittle fracture due to flaws and affect process yield. The starting material is usually in powder form. UO<sub>2</sub> pellets are obtained by pressing powder, sintering and finish grinding. Large powder blends are usually accepted for pressing and sintering after evaluating a small representative powder sample by conducting a sinterability test under regular process conditions. On the other hand, this paper recommends activated sintering conditions, such as those achieved with additives or sintering atmosphere control. Many defects in ceramics have origins in the powder. For example, large hard agglomerates in the powder can cause packing difficulties in pressing. Defects that are not detected in normal sintering may be noticed more readily in activated sintering due to defect amplification. In sintering, open porosity ceases after reaching a density of ∼93 % TD. The residual closed porosity tends to shrink on further sintering. The temperature at which open porosity or permeability is lost shifts to a lower temperature in activated sintering. Yet, activated sintering is to be carried out at conventional high sintering temperature, to be able to amplify and expose pellet defects due to powder. Desintering is a result of large sized packing defects in the green body and premature loss of open porosity in the course of sintering. A descriptive model of desintering is suggested that takes into account powder specific surface area, sintering additive and atmosphere. There is no desintering when green microstructure is homogeneous with no density gradients and with uniformly distributed fine voids that shrink and close during sintering. A high-quality powder sample is one that results in high pelleting yield both in conventional and activated sintering. The low temperature sintering process for UO<sub>2</sub> manufacture that did not progress due to thermal stability concerns in nuclear reactor, may be revived to lower nuclear fuel costs.</div></div>","PeriodicalId":373,"journal":{"name":"Journal of Nuclear Materials","volume":"604 ","pages":"Article 155531"},"PeriodicalIF":2.8000,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Nuclear Materials","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022311524006329","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Ceramics fail by brittle fracture due to flaws and affect process yield. The starting material is usually in powder form. UO2 pellets are obtained by pressing powder, sintering and finish grinding. Large powder blends are usually accepted for pressing and sintering after evaluating a small representative powder sample by conducting a sinterability test under regular process conditions. On the other hand, this paper recommends activated sintering conditions, such as those achieved with additives or sintering atmosphere control. Many defects in ceramics have origins in the powder. For example, large hard agglomerates in the powder can cause packing difficulties in pressing. Defects that are not detected in normal sintering may be noticed more readily in activated sintering due to defect amplification. In sintering, open porosity ceases after reaching a density of ∼93 % TD. The residual closed porosity tends to shrink on further sintering. The temperature at which open porosity or permeability is lost shifts to a lower temperature in activated sintering. Yet, activated sintering is to be carried out at conventional high sintering temperature, to be able to amplify and expose pellet defects due to powder. Desintering is a result of large sized packing defects in the green body and premature loss of open porosity in the course of sintering. A descriptive model of desintering is suggested that takes into account powder specific surface area, sintering additive and atmosphere. There is no desintering when green microstructure is homogeneous with no density gradients and with uniformly distributed fine voids that shrink and close during sintering. A high-quality powder sample is one that results in high pelleting yield both in conventional and activated sintering. The low temperature sintering process for UO2 manufacture that did not progress due to thermal stability concerns in nuclear reactor, may be revived to lower nuclear fuel costs.
期刊介绍：
The Journal of Nuclear Materials publishes high quality papers in materials research for nuclear applications, primarily fission reactors, fusion reactors, and similar environments including radiation areas of charged particle accelerators. Both original research and critical review papers covering experimental, theoretical, and computational aspects of either fundamental or applied nature are welcome.
The breadth of the field is such that a wide range of processes and properties in the field of materials science and engineering is of interest to the readership, spanning atom-scale processes, microstructures, thermodynamics, mechanical properties, physical properties, and corrosion, for example.
Topics covered by JNM
Fission reactor materials, including fuels, cladding, core structures, pressure vessels, coolant interactions with materials, moderator and control components, fission product behavior.
Materials aspects of the entire fuel cycle.
Materials aspects of the actinides and their compounds.
Performance of nuclear waste materials; materials aspects of the immobilization of wastes.
Fusion reactor materials, including first walls, blankets, insulators and magnets.
Neutron and charged particle radiation effects in materials, including defects, transmutations, microstructures, phase changes and macroscopic properties.
Interaction of plasmas, ion beams, electron beams and electromagnetic radiation with materials relevant to nuclear systems.
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