Production of ⁵¹Cr by proton irradiation of ^natV and purification by precipitation and ion exchange chromatography

European demand for chromium has grown dramatically, leading to the need for a detailed understanding of recycling of steel sludges and separation methods. To simulate these processes, we will use the radiotracer technique. ⁵¹Cr (T_1/2 = 27.7 d) was choosen as a radionuclide. The isotope can be produced by the nuclear reaction ^natV(p,n)⁵¹Cr at a cyclotron. We used our recently installed cyclotron Cyclone^® 18/9 (IBA) for the irradiation of ^natV (99.75% ⁵¹V). The vanadium foil was put in an aluminium holder with a diameter of 10 mm and a depth of 100 µm. The target was covered by a 100 µm thick aluminium foil. The irradiation was done at a beam of 16 MeV protons and a current of 10 µA for 4 hours. For the separation of ⁵¹Cr we established a multistage treatment. After cooling for 20 hours, the vanadium foil was dissolved with 2 ml conc. nitric acid. After addition of 20 mg iron(III) chloride, the hydroxide was subjected to a threefold cycle of precipitation with ammonia and dissolution with nitric acid. Vanadium(V) is soluble under these conditions. The separation of the radionuclide ⁵¹Cr and iron(III) was performed by ion exchange chromatography with AG 1-X8 (BIORAD) in conc. HCl. The ⁵¹Cr solution was eluted on the resin and the resin was washed six times with 2 ml conc. hydrochloric acid to remove the iron(III). The combined ⁵¹Cr solutions were evaporated to dryness and the residue was dissolved in 0.01 M sulfuric acid. The detection of ⁵¹Cr was done by gamma-counting (320 keV; 9.91%). The radiochemical yield was 66% at a production rate of 0.575 MBq/µAh.