抄録
Analyses of ruthenium-106 in marine environmental samples, which are useful for monitoring within a control context, have been developed. The quantity and the quality of the samples applied for the analyses are as follows : two l of sea water filtered through a millipore filter of 0.45 E.cm pore size; two g (wet weight) of bottom sediments prepared by sieving in sea water ; or the edible part of marine organisms equivalent to ca. 1 g ash. In order to equilibrate 106Ru in the samples with ruthenium carrier and to dissolve the samples completely, marine organisms and sediments are ashed at 400-500°C, and then fused with a mixture of potassium hydroxide and potassium nitrate. Sea water is heated in the presence of an oxidant in an alkaline medium. Ruthenium is extracted with carbon tetrachloride as ruthenium tetroxide, and then back-extracted with sodium hydroxide solution containing a reducing agent. Hydrous ruthenium oxides are precipitated from the extract and subjected to β-activity measurement with a low background gas-flow counter by use of a 40 mg/cm2 aluminum absorber. The loss of ruthenium throughout ashing and chemical procedures was found to be negligibly small by a tracer experiment. Chemical yields were 89±5 % and the ratio of chemical and radiochemical yields was 0.98±0.03. Sensitivity of the method (3σ) is 0.2 pCi and the whole chemical procedure takes 3 ?? 4 hours. Decontamination factors for the other activities were: > 3 × 104 for 54Mn and 59Fe, 3 × 103 for 60Co, 85Sr and 131I, 2×103 for 137Cs, 1×103 for 65Zn and 95Zr-95Nb, and approximately 102 for radionuclides of thorium and uranium series. A rapid γ-spectrometric technique for 106Rh has also been developed in which 106Ru was coprecipitated with cobalt sulfide from sea water.
