Separation of plutonium from uranium and fission products by adsorption

摘要

Plutonium is recovered from an aqueous solution in which it is present together with uranium or fission products or both, by preferential adsorption of plutonium on diatomaceous earth, fuller's earth, silica gel, or magnesium silicate. Neutron-irradiated uranium may be dissolved in nitric acid and the solution contacted with the adsorbent, preferably at a pH of 2.3-3.7. The concentration of uranyl nitrate in the solution is preferably below 30 per cent. Plutonium may be eluted from the adsorbent with 6N nitric acid of the fission products, a high proportion of columbium is adsorbed, lesser amounts of zirconium, and very small amounts of other fission products, e.g. barium and lanthanum. To separate columbium and zirconium from plutonium, the plutonium may be precipitated in its lower oxidation state with fluoride ion; alternatively the plutonium may be eluted from the adsorbent with ammonium carbonate solution, leaving some fission products behind. Experiments are described showing (a) the suitability of diatomaceous earth for re-use as an adsorbent after elution with nitric acid; (b) the effect on the amount of plutonium adsorbed of the pH of the aqueous solution and the concentration of uranyl nitrate; (c) the maximum pH to which uranyl nitrate solutions of different concentration may be raised without causing precipitation; (d) the raising of the pH of the first portion of a solution passed through a column of diatomaceous earth; (e) the strength of acid necessary for elution of the plutonium; (f) the effect of bombardment by deuterous of the diatomaceous earth adsorbent; (g) the amounts of plutonium and fission products adsorbed on a column of silica gel.