Conceptual model for decision support in mining industry NORM - aspects of environmental radiation protection

Mining like many other industries can cause environmental impact. One of aspects that is in focus in many countries concerns to quantify the impact and establish requirements or improve the existing regulation about naturally occurring radioactive material - NORM. By a suitable management of the activities in these industries, there is an effort to minimize the waste production, minimize the environmental impacts and, consequently, the exposure of members of the public and workers. This study developed a conceptual model, a tool to assist in the decision making process for managers of mining and industrial facilities that deal with NORM. To develop this model, the Brazilian regulations were confronted with the regulations of countries where the NORM subject is important and with those that are being established by the principal institutions of radioprotection. The need of updating the Brazilian regulations was observed. Some recurring themes that are relevant to the management of NORM industries were surveyed, which resulted in the insertion of non-human biota risk assessment and the participation of stakeholders in the proposed model. The model was applied to a real case, the phosphoric acid and uranium plant of Santa Quiteria, in the Ceara state, with the aim of identifying the main critical points of the facility from the perspective of the environmental radiological impact and evaluating the adequacy of model, in addition to providing subsidies for its improvement. By the assessment of the process, it was found that the main source would be the phosphogypsum stack, which ²²⁶Ra activity concentration might exceed the level established for its use in agriculture and cement industry. The impact assessment was carried out in three different scenarios: 1) the critical group located in the facility borders, 2) the critical group located on the stack, after the closure of the area and 3) workers. In all cases, the exercise pointed out the exceeding of the adopted dose levels, 1 mSv /y for public and 6 mSv /y for workers. The assessment carried out in a holistic manner, showed that non-human biota might also be affected by the contamination of surface waters. The simulation spotlighted the importance of the stack geometry and the rainfall erosion index for the environmental contamination, as well as the importance of planning the decommissioning of the facility, still in the planning phase, in order to give support for the feasibility studies of the project. Although quite conservative, the adopted methodology for assessing the dose was useful to guide the second step of the process which is a survey of data and local information, aiming a more realistic approach. (author)