Dose distribution behaviour of the IPEN-CNEN/Brazil workers

The Instituto de Pesquisas Energeticas e Nucleares, IPEN, in Brazil has a major role in several fields of the nuclear activity, such as radiation and radioisotope applications, nuclear research reactor, testing materials and fuel cycle and radiological protection and dosimetry. The goal of this paper is to present the dose distribution behaviour of occupational radiation exposures of the monitored workers at IPEN during the years 2000 to 2007. This study is based on the dose registry data, obtained by Thermoluminescent Dosimetry to the whole body and acquired by Thermoluminescent Dosimetry Laboratory of the IPEN. The TLDs are usually positioned on the trunk between the waist and shoulder that is the part of the body with the highest exposure rate. In this study the average of 740 monitored workers over the years, meaning 100% of the participants, was considered. The results show that the values of effective dose obtained are in reasonable agreement with national regulations. The average annual effective dose in the period considered, was 3.52±0.48 mSv with a maximum value of 23.31 mSv in 2001. The average and maximum values of the effective doses represent approximately 17.6% and 116.6% of the annual effective radiation dose limit, according to the recommendation of the International Commission on Radiological Protection. The overall distribution allowed the comparison of all doses reported and did not exceed the effective dose of 20 mSv per year, average over defined 5 year period. In this time period the effective dose did not also exceed 50 mSv in any single year. (author)