(Solved): A short-lived radioisotope yttrium- 90 can be separated by solvent extraction, leaving the parent ...

A short-lived radioisotope yttrium- 90 can be separated by solvent extraction, leaving the parent radionuclide Sr-90 in the aqueous phase. Their half-lives are \( \mathrm{T}_{1 / 2}(\mathrm{Sr}-90)=28.78 \mathrm{y} \), \( \mathrm{T}_{1 / 2}(\mathrm{Y}-90)=64 \) hours \( =2.67 \) days. After splitting phases you have found that the \( 0.5 \mathrm{~mL} \) aliquot of the Sr-eluate counts \( 250 \mathrm{~d} / \mathrm{s} \). a) How long you can use this Y-free solution of Sr-90 for your research work if the activity of growing Y-90 cannot exceed \( 10 \% \) of Sr-activity? b) What will be the total activity of the Sr-eluate after one month?