Recovery of protactinium from irradiated thorium nitrate by solvent extraction is studied in relation to the blanket conditions of a fusion neutron source (FNS) using -octanol and diisobutylcarbinol (DIBC) as extractants. The degree of extraction of Pa from a solution of irradiated thorium nitrate (600 g/dm) in 3 M nitric acid in one contact exceeded 80%, and the separation coefficients from uranium and thorium were obtained to be more than 600 and 130 000, respectively. To minimize the content of U in U (to less than 5 ppm), a procedure is proposed that includes short-term irradiation of thorium nitrate and continuous extraction of protactinium.