A Prospective Radiological Risk Assessment for a Phosphate Industry Project

The Santa Quitéria Project is the major Brazilian uranium mine project, nowadays. A peculiarity of this project is the association of uranium with phosphate and the mining and processing of both by two different enterprises. A private company will be responsible for the production of phosphoric acid and a state owned company will be responsible for the production of yellow cake. At full capacity, the facility will generate 10% of Brazil’s total annual phosphoric acid production and 1,500 tons of yellow cake per year. The processing by which phosphoric acid is produced generates phosphogypsum (PG) as a by-product. The ratio of phosphogypsum to phosphoric acid is around 5 to 1. After all the phosphate has been extracted and processed, it is expected that some 37 million tons of phosphogypsum with 13 Bq/g of Ra will be produced. A prospective generic assessment was carried out for evaluating the potential radioactive impact of this PG stack on the workers and surrounding inhabitants. Two hypothetical farmer scenarios were designed to estimate the potential dose out of the project boundary and over the stack piles, after the shutdown of the project. The annual exposure dose of workers was also evaluated. As a result, the potential public and worker doses exceeded the adopted level of doses of 1mSv.y and 6 mSv.y, respectively. The simulation spotlighted the importance of the rainfall erosion index, and consequently the stack shape for the environmental contamination. The importance of planning the decommissioning of the facility still in the planning phase of the project to give support for the feasibility studies was also highlighter. Although quite conservative, the prospective assessing of dose herein is useful to aware and guide the decision makers on information and data survey and taking avoiding action to protect the health, by changing the project in some way.