Development of semi-automated system for preparation of 188Re aqueous solutions of high and reproducible activity concentrations

A semi-automated system has been developed for elution and concentration of the 188Re-eluate from 111 GBq (3 Ci) 188W/188Re-generators to provide a dissolved β-source of high 188Re-activity per unit volume. The elution progress and concentration were precisely and continuously monitored by use of collimated diode detectors. By using ion exchange cartridges, small eluate volumes (2-3 ml) of maximum 40 GBq, 188Re/ml activity concentration were routinely prepared. The concentrated 188Re solutions were used to β-irradiate aqueous suspensions and solutions of iodine species to evaluate a simulation of the extent of radiolytic decomposition of chemical species (AgI and CH3I) expected to accumulate in the containment sump of a nuclear reactor in the event of a severe accident with reproducible dose rates of up to 0.4 Gy s−1. Results have shown that AgI colloidal particles decompose to varying extents, depending on conditions, and in proportion to their initial mass, which indicates surface oxidation. Experiments have also confirmed CH3I decomposition in proportion to initial aqueous concentration.