[en] The chemical yield of technetium by an anion exchange (AG 1-X₄) procedure is determined under different conditions from 200 liters sea water. A new method for collection ⁹⁹Tc from 200-400 liters sea water has been developed by anion exchange. The evaporation rates of RuO₄ and TcO₄^- are determined at 100 deg. C in 0.1 N H₂SO₄. A higher decontamination factor 2.5 x 10⁵ - 2.4 x 10⁷ for ruthenium is obtained by evaporating the RuO₄ at 100 deg. C in 0.1 N H₂SO₄. The ruthenium is oxidized to RuO₄^- with NaC1O at pH = 9. Fe(OH)₃ scavenging, AgCl precipitation and 5% TIOA/xylene extraction at controlled valence are used for decontamination of ruthenium, ^110mAg and other nuclides. The chemical yield of technetium-99 in the procedure is about 70%. (author)