India

The facility is located in the Internal Dosimetry Section of the Health Physics Division (Low-level Counting Laboratories) at Bhabha, Atomic Research Center, Deonar, Mumbai. Approximately 300 measurements are performed annually for transuranics, with another 150 measurements for uranium and 25 measurements for thorium. About 5% of the measurements are performed on females. There are two counting rooms in a common shield; the larger room is used for gamma ray measurements of the whole body, and the smaller, for lung counting. The size of the smaller room is 2.4 m long by 1.9 m wide by 1.8 m high. The outer walls are 200 mm of steel, and a wall of 152 mm of steel separates the two rooms. The smaller room is lined with 3 mm of lead, 2 mm of cadmium, and 0. 5 mm of copper. A flat bed is contained in each room. Intercomparison Measurements. At BARC, two types of measurements were made: a) with the standard point sources in a chosen standard geometry for each detector used for the phantom measurements and b) with the Reference Asian Phantom and chest overlays including measurements with blank and radioactivity loaded lung sets. A number of detection systems were employed for these measurements in a variety of counting geometries over the phantom. Three types of phoswich detectors operating with their optimized PSD electronics, were calibrated. Each phoswich detector was used in a suitable counting geometry and measurements were made for all the actinides except natural thorium. The detectors used were: i) A 20 cm diameter phoswich that had been in use for many years, ii) A new 20 cm diameter phoswich and, iii) A square phoswich with an area of 103.2 cm2. Two types of NaI(Tl) scintillation detectors were used: i) A 20 cm diameter x 10 cm thick detector in two counting geometries - static and dynamic (linear scan) for measurements of 232Th and its daughters and, ii) A 12.7 cm diameter x 1.27 cm thick detector in a twin detector geometry with the measurements being made for all actinides except 238Pu and 232Th. Finally, a single hyper pure (HP) Ge detector, 51 mm diameter and 18.5 mm sensitive depth, (LO-AX) was used in two configurations: a chest mapping configuration and an array consisting of four detectors. These measurements were made only for 238Pu and 241Am lungs. A brief description of the radiation detectors, their associated electronics, shielding, counting geometries employed, and a summary of data on reference point sources and Reference Asian Phantom are given