Plutonium microspheres

Anderson E, Holland L, Prine J, et al. 1974. Lung irradiation with static plutonium microspheres. In Karbe E, Park J, eds. Experimental lung cancer. Carcinogenesis and bioassays. New York Springer-Verlag, 430-442. 

Uranium and mixed uranium—plutonium nitrides have a potential use as nuclear fuels for lead cooled fast reactors (136—139). Reactors of this type have been proposed for use ia deep-sea research vehicles (136). However, similar to the oxides, ia order for these materials to be useful as fuels, the nitrides must have an appropriate size and shape, ie, spheres. Microspheres of uranium nitrides have been fabricated by internal gelation and carbothermic reduction (140,141). Another use for uranium nitrides is as a catalyst for the cracking of NH at 550°C, which results ia high yields of H2 (142). 

Interest in the so-called sol-gel process for the remote-controlled manufacture of plutonium-containing fuel rods is increasing due to its high safety. In this process a filter cake of freshly precipitated uranium(IV) oxide is converted ultrasonically into a U02-gel, which after drying is fired at 1150°C. The resulting microspheres, 40 to 60 t,m in diameter, are then poured into casing tubes using vibratory techniques. 

Plutonium dioxide microspheres (149 to 177-ym diam) were contacted with 10"3 M biocarbonate buffer (pH 7) for various periods of time. Some of the microspheres had been pre-incubated in pH 4 acetate buffer for two years prior to the bicarbonate experiments. Other microspheres were contacted with bicarbonate solution without any prior contact with water. The microspheres were primarily 239Pu (88.9% of Pu mass). The microspheres had been calcined at 1150°C and had a specific surface area of 0.012 m2/gram. 

Table III. Plutonium Species Identified in pH 7.0 Sodium Bicarbonate Solutions Contacting High-Fired Pu02 Microspheres...

Switzerland Within the framework of the CAPRA project, the fuel option for amplified plutonium consumption is being studied. In the area of materials for actinide transmutation, the following tasks has been completed in 1994 (1) preparatory experiments and solubility tests for (Ui, PUJ O2 (0.25 < x < 0.65 and for (Uj., PU,J N (0.25 < x< 0.75), as possible materials for the efficient fission of plutonium in a fast neutron flux (2) fabrication of pure PuN-microspheres for ceramic-metal fuel (3) design calculations for sphere-pac segments, based on the idea of a ceramic-metal fiiel (4) material preparation of (U, Zr) N and pelletization tests of TiN and (U, Zr)N for the irradiation experiment in the reactor PHENIX (5) experimental preparations of (Ce,U) O2, (Ce,U,Pu)02 and (Ce, PU)02 for the CAPRA core with lower Pu content, and (6) cleaning of americium from waste streams of the plutonium separation equipment (extraction chromatography). 

To limit the plutonium enrichment in fresh fuel to the allowable level in Japan, the Clean Burn concept employs Pu02 in an inert YSZ microsphere kernel. It avoids mixing with uranium so that no additional plutonimn is generated during a fuel bumup... 

---