Low-temperature sintering(LTS)experiments of UO2 pellets and their results were reported.Moreover,a routine process of LTS for UO2 pellets was primarily established.Being sintered at 1 400 ℃ for 3 h in a partially-ox...Low-temperature sintering(LTS)experiments of UO2 pellets and their results were reported.Moreover,a routine process of LTS for UO2 pellets was primarily established.Being sintered at 1 400 ℃ for 3 h in a partially-oxidative atmosphere,the relative density of the pellet can be up to around 94%.Pellets with such a high density are of benefit for following-up reduction-sintering processes.Orthogonal test indicates that the importance of factors affecting the density decreases in the sequence of partial-oxidative sintering temperature and time,reduction-sintering time and temperature,and sintering atmosphere.It is found that it is helpful to introducing a small amount of water vapor into the sintering atmosphere during the latter stage.It is believed that it is the key factor to raise the O/U ratio of original powder in order to improve the properties of the low-temperature sintered pellets.展开更多
For an analysis of the oxidation behavior of UO2 nuclear fuel pellet under a loss of water coolant accident in a spent nuclear fuel pool of an LWR, thermodynamic assessments of UO2 oxidation were carried out under var...For an analysis of the oxidation behavior of UO2 nuclear fuel pellet under a loss of water coolant accident in a spent nuclear fuel pool of an LWR, thermodynamic assessments of UO2 oxidation were carried out under various atmospheric conditions. In a steam atmosphere, it was assessed that UO2 would not be fully oxidized into U3O8 due to the relatively lower oxygen partial pressure, while UO2 will be fully oxidized into U3O8 in an air atmosphere. In an air and steam mixture atmosphere, the UO2 oxidation was dominantly affected by the air volumetric fraction, because of the relatively higher oxygen partial pressure of air. In addition, the effect of H2 volumetric fraction on the oxygen partial pressure under a mixture atmosphere was calculated, and it was revealed that UO2 pellet oxidation could be reduced above the critical value of H2 volumetric fraction.展开更多
文摘Low-temperature sintering(LTS)experiments of UO2 pellets and their results were reported.Moreover,a routine process of LTS for UO2 pellets was primarily established.Being sintered at 1 400 ℃ for 3 h in a partially-oxidative atmosphere,the relative density of the pellet can be up to around 94%.Pellets with such a high density are of benefit for following-up reduction-sintering processes.Orthogonal test indicates that the importance of factors affecting the density decreases in the sequence of partial-oxidative sintering temperature and time,reduction-sintering time and temperature,and sintering atmosphere.It is found that it is helpful to introducing a small amount of water vapor into the sintering atmosphere during the latter stage.It is believed that it is the key factor to raise the O/U ratio of original powder in order to improve the properties of the low-temperature sintered pellets.
文摘For an analysis of the oxidation behavior of UO2 nuclear fuel pellet under a loss of water coolant accident in a spent nuclear fuel pool of an LWR, thermodynamic assessments of UO2 oxidation were carried out under various atmospheric conditions. In a steam atmosphere, it was assessed that UO2 would not be fully oxidized into U3O8 due to the relatively lower oxygen partial pressure, while UO2 will be fully oxidized into U3O8 in an air atmosphere. In an air and steam mixture atmosphere, the UO2 oxidation was dominantly affected by the air volumetric fraction, because of the relatively higher oxygen partial pressure of air. In addition, the effect of H2 volumetric fraction on the oxygen partial pressure under a mixture atmosphere was calculated, and it was revealed that UO2 pellet oxidation could be reduced above the critical value of H2 volumetric fraction.
