Dose assessment to workers in a dicalcium phosphate production plant

• Published in: Journal of environmental radioactivity 2016-12, Vol.165, p.182-190
• Main Authors: Mulas, D., Garcia-Orellana, J., Casacuberta, N., Hierro, A., Moreno, V., Masqué, P.
• Format: Article
• Language: English
• Subjects: Aerosols; Air Pollutants, Occupational - analysis; Air Pollutants, Radioactive - analysis; Air Pollution, Radioactive - statistics & numerical data; Ambient dose equivalent H; Background Radiation; Calcium phosphate; Calcium Phosphates; Contaminació atmosfèrica; Degradació ambiental; Desenvolupament humà i sostenible; Dicalcium phosphate plant; Economia i organització d'empreses; Fosfat de calci; Humans; Industrial safety - Península Ibèrica; NORM; Occupational effective dose; Occupational Exposure - statistics & numerical data; Prevenció de riscos laborals; Radiation Dosage; Radiation Exposure - statistics & numerical data; Radiation Monitoring; Radon; Seguretat en el treball - Península Ibèrica; Seguretat industrial; Àrees temàtiques de la UPC
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2016.09.018

The production of dicalcium phosphate (DCP) uses phosphate rock (PR) as a raw material. Sedimentary phosphate rocks are enriched with relevant concentrations of natural radionuclides from the 238U decay chain (around 103 Bq·kg−1), leading to the need of controlling potential exposures to radiation of workers and members of the public in accordance with IAEA safety standards. Indeed, phosphate industries are classified as Naturally Occurring Radioactive Material (NORM) industries. Thus, the aim of this work is to assess the radiological risk of the workers in a DCP production plant located in the Iberian Peninsula (South-West Europe), which digests PR with hydrochloric acid. In the present study 238U, 230Th, 222Rn, 210Pb and 210Po concentrations in aerosols (indoor and outdoor areas) are reported. Aerosols showed concentrations between 0.42–92 mBq·m−3 for 238U, 0.24–33 mBq·m−3 for 230Th, 0.67–147 mBq·m−3 for 210Pb and 0.09–34 mBq·m−3 for 210Po. Long-term exposure (four months) of passive 222Rn detectors provided concentrations that ranged from detection limit (< DL) to 121 Bq·m-3 in outdoor areas and from < DL to 211 Bq·m−3 in indoor areas, similar to concentrations obtained from short-term measurements with active detectors from < DL to 117 Bq·m−3 in outdoor areas and from < DL to 318 Bq·m−3 in indoor places. 226Ra accumulation in ebonite and pipe scales were the most important contributions to the ambient dose equivalent H*(10), resulting in 0.07 (background)–27 μSv·h−1 with a median value of 1.1 μSv·h−1. Average 222Rn air concentrations were lower than the 300 Bq·m−3 limit and therefore, according to European Directive 2013/59/EURATOM, 222Rn concentration is excluded from the worker operational annual effective dose. Thus, considering the inhalation of aerosols and the external dose sources, the total effective dose determined for plant operators was 0.37 mSv·y−1. •External dose is the major contributor to the NORM annual effective dose.•238U, 230Th, 210Pb and 210Po were quantified in atmospheric particles.•Mean 222Rn concentrations were lower than 300 Bq·m−3.•Plant operator annual effective NORM dose was lower than 1 mSv·y−1.