Recycling Process for Sinter-Active U3O8 Powders

Abstract

The effect of the oxidation temperature of UO 2 pellets on the powder properties of oxidized U 3 O 8 powders has been investigated. The powder morphology, crystalline size, and BET surface area of recycled U 3 O 8 could be modified by controlling the oxidation temperature of the UO 2 pellets. Recycled U 3 O 8 powder with a high BET surface area and a small particle size could be obtained by lowering the oxidation temperature. It was also found that this low-temperature-oxidized sinter-active U 3 O 8 powder is effective in mitigating the density drop of the UO 2 pellets when the recycled U 3 O 8 powder is added. Moreover, the recycled powder acted as a grain-size-enlarging promoter in the UO 2 pellets.

RECYCLING PROCESS OF U3O8 POWDER IN MnO-Al2O3 DOPED LARGE GRAIN UO2 PELLETS

“…U3O8 powders were prepared by heating those pure UO 2 pellets and reference UO 2 pellets in air for 24hrs at 325°C and 450°C, respectively. The UO 2 pellets were fully oxidized to U3O8 single phase after the heat treating as shown in the previous work [13]. For convenience, we will refer to the above two U3O8 powders obtained from the reference UO 2 pellets as 'raw U3O8 powders', hereafter.…”

“…KEYWORDS : Doped Large Grain Pellet, Recycling Process, MnO-Al2O3, U3O8 Powder that dealt with the heat treatments of recycled U3O8 powder to improve its sintering properties [10][11][12][13]. It is known that a lowering oxidation temperature, mechanical ball-milling, and sequential cyclic heat treatment of oxidation and then reduction could enhance the recycled U3O8 powder properties.…”

Oxidation of UC: An in situ high temperature environmental scanning electron microscopy study

“…The next image, Figure 4f, captured 15 seconds later demonstrates the quasi-instantaneous change in sample morphology. Figure 4c shows the oxide morphology after the explosive event which has a structure that is opened in comparison to the oxide shown in Figure 2c and shows the characteristic popcorn-like morphology of U3O8 formed by UO2 oxidation 17,37 .…”

“…UC oxidised as soon as oxygen was added to the chamber, no induction period was observed and sample area expansion and crack propagation grew exponentially until reaching the point of no-return where explosion occurred. The characteristic popcorn-like morphology of U3O8 previously reported in the literature 17,37 for the conversion from UO2 to U3O8 was monitored during in situ oxidation of UC in the range of temperature from 723 to 848 K. The influence of surface morphological changes such as crack propagation was here used to describe the mechanism of oxidation and ignition of UC. The characterisation of oxidation mechanisms via crack analysis is an unusual method in comparison with the widely used method of weight gain curves.…”

Impurity analysis and dissolution behaviour of plutonium bearing impure MOX scrap: an assessment of recycling feasibility

“…In the area of recycling of the clean plutonium bearing MOX scrap, several processes have been reported in the literature [11][12][13][14][15][16][17][18][19]. These processes are categorized as wet and dry, based upon the involvement of wet chemical processing.…”