Urinary Excretion of 239Pu by the General Population: Measurement Technique and Results

A technique for measuring ultra-low levels of 239Pu in urine samples from persons without any occupational exposure has been developed in this laboratory. We have analysed urine samples ranging from 200 ml to 8.1. Briefly, the technique involves co-precipitation of plutonium, dissolution in 8N HCl = Cl2 and separating plutonium through anion exchange columns. Plutonium is eluted directly onto lexan slides in four drops. The slides are dried, packed in a 'rabbit' and sent to a well thermalised research reactor for irradiation to a fluence of 1017 n.cm-2. Subsequent to irradiation, tracks are elicited by etching in caustic solution and optically counted. The mean recovery of plutonium was 75% and the detection limit for a 4 litre urine sample was 0.2 µBq.l-1. The results suggest that urinary excretion of plutonium in persons born in 1958 or earlier which range from -0.08 to 3.4 µBq.l-1 with a mean of 0.6 µBq.l-1 and median of 0.4 µBq.l-1, exceeds that from persons born after 1961 which showed a mean of 0.3 µBq.l-1.