A process for purifying a stock Sr-90 solution containing stable and radioactive impurities, holding the purified Sr-90 solution for Y-90 ingrowth, and subsequently extracting the Y-90 from the Sr-90/Y-90 solution. The stock solution is sequentially passed through two thermoxide-type sorbents (T-3 and T-5), which hold the impurities while passing the Sr-90 solution. After ingrowth of Y-90, the Sr-90/Y-90 solution is passed through sorbent T-3, which preferentially sorbs the Y-90 while passing the Sr-90 solution. The Y-90 is then eluted from the T-3 sorbent. The T-3 and T-5 sorbents are specially prepared compounds of zirconium dioxide and titanium dioxide, respectively, that preferentially sorb Y-90 under predetermined conditions of solution pH and NaCl concentration.