The Whole Body Monitor HUGO II at Studsvik. Design and Operation

The whole body monitor laboratory at Studsvik is presented with special attention to descriptions of localities, equipment, calibration and types of measurements. The main monitor, shielded by 53 tons of iron, is equipped with a 8 in. diam. x 4 in. Nal(Tl) detector and a 512- channel Nuclear Data analyzer and located at ground level in the Health and Safety Laboratory a few hundred metres from the various laboratories and reactors at Studsvik. Since the start in June 1963 and up to January 1969 more than 4,500 measurements have been performed, most of them for radiation dose control purposes. In about 40 % of these latter measurements, internal contamination exceeding the normal detection limit of a few nCi has been observed. Only a few cases so far have exceeded the maximum permissible quarterly dose set by ICRP