Sublimation and thermochromatography of lower actinide and lanthanide oxides

Sublimation in helium and hydrogen flow of 244Cm, 241Am, 240Pu, 237Np and U actinide microquantities applied in oxide form to different metal surfaces is studied. With the temperature below 1200 deg C actinides were not sublimated (<0.1%) from the surface of Ta, W, Ni steel and from Pt (in the last case inward metal diffraction is observed). From the surface of metallic Ti, Zr all mentioned actinides were sublimated at 1200 deg C with the yield of more than 95% for 30 min (macroquantities of U - 50%) and completely precipitated at the same temperature in Ta, W or quartz collectors. Am sublimation from Ti, Zr surfaces began at 800 deg C, of Cm - above 1000 deg C. Efficient activation energy of Am sublimation from Ti surface is 153+-13 kJ/mol, from Zr surface - 123+-8 kJ/mol. In experiments on thermochromatography of Am, Cm, Pu and of carrier-free 139Ge, 169Yb, 173Lu in titanium columns in helium flow with deep purification from O2 all these elements were transported upto comparatevely low temperatures - about 570 deg C. With the raise of oxygen content in the system precipitation temperature increased upto 1100 deg C. Adsorption heat values calculated from thermochromatographic data were from 188+-3 to 301+-4 kJ/mol. No suffucient difference in behaviour of studied elements is observed