Natural radioactivity in Italian ceramic tiles

Zircon is the mostly widely occurring zirconium-containing mineral mined commercially. Thorium and uranium may substitute for zirconium in the zircon crystal lattice. The radioactivity levels in zircon lies typically within the ranges 500–1000 Bq kg -1 for 232 Th and 1000–5000 Bq kg -1 for 238 U [1]. One of the most important use of zircon is as opacifier for ceramic tiles. Body of ceramic tiles is a mixture of different raw materials, including: clays, quartz materials and feldspathic materials. The body may be glazed or left unglazed. Due to the presence of zircon in the glaze or in the body, ceramic tiles can show natural activity concentration significantly higher than the average values of Earth's crust. This study contains a summary of results obtained by a survey on Italian ceramic tiles collected over three years (2005–2007). About one hundred ceramic tiles were analysed. The survey consisted of measurement of 226 Ra, 232 Th and 40 K activity concentrations and of the gamma-index [2] and radium-equivalent [3, 4] calculation. The activity concentrations of 226 Ra, 232 Th and 40 K result in the order of 100, 50 and 500 Bq kg -1 , respectively. Gamma index and radium equivalent activity have been found well below the acceptable limit in most of the samples.