Potential exposures in mobile industrial radiography

The radiation protection conditions of the mobile or open industrial radiography facilities were analyzed in the period from 1992 to 1996 to estimate the value of the potential exposure risk, the mean annual dose and the dose distribution function of the workers. To estimate the potential exposure the concepts described in ICRP 64 and Safety Series 104 were used. The annual mean value of abnormal events occurred in the operations of to remove and to retract the radioactive source of exposure device recorded in data bank of National Commission of Nuclear Energy (CNEN), in a period of 5 years, were used to obtain the risk value. To evaluate the worker exposures, data obtained by accompaniment the radiographic testing in 5 installations, representative of all radiographic facilities in Brazil and the data bank of CNEN were used. To obtain the statistical dose distribution data from individual monitoring of the workers of these installations were used, data from additional individual monitoring and data bank of CNEN. The absorbed mean dose value in the period from 1992 to 1996 maintained about 0.2 mSv/year like as in the period from 1990 to 1994, with a maximum value of 0.55 mSv/year in 1988. The statistical distribution in a period from January to December 1996, behavior likes as long-normal type. The estimated risk value for potential exposure was 4x10-6 per year, in the period from 1992 to 96. Using the data bank of CNEN, in a period from 1976 to 1992, the estimate value was 6.6x10-6 per year, using the same methodology. The comparison of the failed operation probability value of operator/device/local system, in a period from 1976 to 1992 and in 1996, shows an increasing of 0.5x10-11 to 1.1x10-11 per year, due mainly to the radiographic device and accessories become oldest, in spite of maintenance care. However, due to the radiation procedure improvements, the potential risk value reduced about 40%, that is from 6.6x106 to 4x10-6 per year. (author)