Determination of radon specific exhalation rate from Italian ceramic tiles.

Porcelain tiles commonly manufactured in Italy have been studied for both natural radionuclide content and radon emanation using high resolution gamma spectroscopy and the E-PERM electret ion chamber, respectively. The measured activity concentrations were 33–257 Bq/kg for U-238, 33–197 Bq/kg for Ra-226, and 39–76 Bq/kg for Th-232; the radon exhalation rates were found to be at or below the lower limit of detection (0.0004 Bq·kg–1·h–1). While previous work on the raw materials for porcelain tiles, such as quartz and zircon sand, showed measurable radon exhalation rates, our results on the end products showed extremely low rates. This observation suggests that it is highly probable for radon present in the tile to be released during the manufacturing process (vitrification); conversely, the radon produced through the decay of radium after the vitrification process remains locked up in the glass-like matrix. Additional measurements are needed to confirm that radon exhalation from porcelain tiles is negligible in terms of the inhalation dose rate.