CHEMICAL PROCEDURES AND COUNTING TECHNIQUES i i itil Strontium-90 is separated by the fuming nitric acid precipitation and then purified through hydroxides and chromates precipitations, The activity of the final strontium carbonate and yttrium oxalate precipitates is measured in low level anticoincidence beta counters, Cesium-137 is measured by direct gamma spectrometry on the unprocessed or dried samples and, whenever it is necessary, by gamma spectrometry after chemical separation. This is performed © by filtration of the solution, obtained dissolving the sample, through a thin AMP (ammonium molybdophosphate) layer, by which cesium is retained, Details of this procedure may be found in the paper by E. Van der Stricht issued ‘on "Radiochemical Acta" 3, 193-199 (1964), Gamma emitting nuclides are measured by direct gamma spectro~ metry, using, also the spectrum stripping technique. is separated by anion exchange and electro- deposition; details of the procedure may be found in the paper by M.C. de Bortoli: "Radiochemical determination of plutonium in soil and other environmental samples", Anal, Chem, 39, 375 (March 1967). The activity is measured in a Frish grid ionisation chamber connected to a multichannel analyser, Oe AE pe UHI, TMI ie ARR RRC Plutonium-239+240 _EXTRAPOLATION OF THE DATA extrapolated to the last day of the collecting period, peg are samen yum dag ee Except when otherwise stated, the data presented in this report TII - 34