Сobalt-60 radionuclide speciation in boric acid solutions

Abstract

In this work, the speciation of 60Co radionuclide in model solution of spent fuel pool coolant is studied by ultrafiltration and centrifugation. The effect of pH and composition of the solution on the 60Co radionuclide speciation is shown; the limitss in existence of ionic and non-ionic (pseudocolloidal) forms are defined. A great part of 60Co states at ionic form represented by hydrated cation of 60Co in the solutions of boric acid 20 g/L at 4–8 pH value. The size of non-ionic forms of 60Co in this pH range is 1–50 nm. Starting with pH 8, the соntent of non-ionic forms increases dramatically and reaches 100 % at pH value 10–11, which is due to formation of CoOH+ ions and their increased sorption activity at forming pseudocolloids. Introduction of iron (III) ions to the solution, which are precursors of corrosion products, shifts the formation of nonionic forms of 60Co to lower pH area.