An Automated Shielded Chair Whole Body Monitor

Whole body/organ counting plays an important role in assessing, limiting and controlling the intakes of radioactive materials by the workers of a nuclear research centre as well as of nuclear industry. The Internal Dosimetry Division of BARC, besides designing, developing, supplying and installing the whole body/organ counting facilities at DAE’s nuclear installations, also operates such facilities for radiation workers of BARC and BRIT (1-2). A totally shielded steel room whole body counter located at BARC Hospital is used for the measurements of body/organ burdens of low energy photon (LEP) emitters like Pu/Am and U which emit photons of energy mostly below about 200 keV. For the assessment of internal contamination due to various fission and activation products like 141Ce, 131I, 137Cs, 58Co, 60Co, 125Sb, 106Ru-106Rh, 95Zr-95Nb etc. which generally emit photons of energy greater than about 150 keV, ‘shadow shield bed’ and ‘shielded chair’ types of whole body monitors located side by side at the whole body monitoring laboratory at Modular Lababoratories, BARC are used. These systems have been operating for more than three decades. Thousands of measurements on the radiation workers of BARC have been made under different types of internal monitoring programmes. The practice followed here has been that all workers are first monitored in the shielded chair, which serves as the quick screening counter. The selected few, who may show significant internal contamination, are then monitored in the shadow shield bed for detailed information. The shadow shield bed has also been employed to conduct in-vivo biokinetic studies of radionuclides present in the human body even at much lower levels (fractions of Recording Levels).