Interpretation on and Dose Criteria for Radiation Protection of NORM Based on Its Exposure Characteristics

A concept figure of radiation protection criteria for Naturally Occurring Radioactive Materials (NORM) is proposed based on a continuous scale without explicit boundaries. The criteria map tries to visually classify various exposures to NORM by the following two axes: category and situation of exposure. Its free division concept by several zones proposed in this study shows us where the target exposure to NORM is positioned in a map for the determination of radiation protection strategy. For example, a target dose within the range of 5 to 10 mSv/y (up to 20 mSv/y) could be considered as one of occupational exposure activities if the frequency is high, even if that might be generally categorized into the existing exposure situation for the public. From an international view, as in Canada, Australia, etc., the concept of controlled area has already been applied in their NORM industries. A NORM worker in these countries is categorized as a kind of radiation worker. Related radiation protection strategies would be determined by the regulatory policy and should be based on the culture of each country. The criteria map proposed by the authors helps to make a rational communication to discuss adequate options for radiation protection on large varieties of NORM exposures.