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A procedure based on chemicsl separation techniques and activation anslysis was developed for the sequential analysis of low levels of /sup 131/I, / Sup 129/I, and natural iodine in environmental samples. The iodine is first separated from the samples by oxidation. The separated iodine is then counted by low-level, beta-gated gamma spectrometry for the measurement of /sup 131/I. The chemical yield for the separation is measured by means of /sup 125/I tracer. Activation analysis is used for measurement of the separated natural iodine (/sup 127/I) and /sup 129/I. The natural iodine is estimated from either the /sup 126/ I or /sup 128/I activity produced in the sample; the induced /sup 130/I is used to estimate the /sup 129/I concentration. The measurement of /sup 130/I at low levels requires specialized counting methods. Interfering activities that may be present in the irradiated sample include /sup 125/I, /sup 126/I, short-lived fission-product iodine activities produced by activation of uranium impurities, and /sup 82/Br from bromine impurities. Since /sup 130/I decays with several coincident gamma rays, multiple gamma coincidence counting techniques can be used to reduce background and discriminate against interfering activities. Severail three- and four-segmented NaI(Tl) detectors were used for these measurements and compared …

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