NaI detector. The contaminated radioactivity of the radiation workers by 131 I was immediately conducted using a WBC (CANBERRA, FASTSCAN model 2250) and counting was repeated again a few days later. The performance of whole body counter was checked by CANBERRA transfer phantom (model 2257) with a mixed source (20 ml vial). The intake was calculated by Apex-Invivo counting software and then corresponding dose in thyroid were estimated by using Integrated Modules for Bioassay Analysis (IMBA) Professional Plus code modules. The body activity due to intake of 131 I and the total effective and equivalent dose in thyroid were also estimated and discussed.