Natural or depleted uranium targets were irradiated in JRR-1 with 10¹¹n/sec⋅cm² flux for 3060hr. After setting the irradiated target aside for a few months in a hot-cave, ²³⁹Pu was isolated by TBP solvent extraction method from bulk of uranium and the fission products and then purified by an anion-exchange method.
It was found that 239Pu thus obtained was not contaminated with uranium and ²¹⁰Po. However, it contained β, γ-activity of about 30 days half-life slightly.