Radiological control in a mine with a naturally-occurring radioactive material -NORM: III assessment of removable surface contamination in a pilot plant

Ore Treatment Unit (OUT) possesses a process laboratory. Considering the uranium ore processing, this laboratory works in close cooperation with the Radiation Protection Service of the Unit. In the year of 2009 a pilot plant for the development of solvent uranium extraction from the phosphate ore of the mine of Santa Quiteria city, in Ceara State, Brazil was developed. In this kind of plant the surface contamination may cause contamination for Occupational Exposed Individuals (OEI). In order to control this kind of contamination and offer a safety work's condition for OEIs, a monitoring program of transferable contamination using swab samples was developed. 162 swabs were made. For the alpha emitters the monitoring results varied from 0.001 Bq cm-2 to 0.014 Bq cm-2, with average value of 0.002 Bq cm-2. For beta emitters the results varied from 0.010 Bq cm-2 to 0.031 Bq cm-2 with average equal to 0.011 Bq cm-2. For alpha emitters, 87.65 % of the results were below 0.004 Bq cm-2, values that are one order of magnitude smaller than the limit and the maximum value stayed in 35 % of the limit for an object to be considered contaminated. For beta emitters, 90 % of the results were below 0.010 Bq cm-2 that corresponds to 25 % of the limit and 100 % were below 0.031 Bq cm-2 below the limit for an object to be considered contaminated. In both cases any object monitored during the operation, was not considered contaminated, proving the good practices employed in the laboratory, resultant of the good planning of the Radiation Protection Service for the operations' process. (author)