Gamma emitting radioactive materials in household dinnerware

Abstract

A variety of commonly available household and tableware items and some specialty glass materials commonly found in everyday life were examined for their radioactivity content with two different detection and measurement methods. Dinnerware is produced mainly from clay and sand at high temperatures. Therefore, it should be expected to have some degree of radioactivity. It is also stored in confined places, which permits radon accumulation. The natural radioactivity due to the presence of 238U, 232Th and 40K in dinnerware used in houses was measured. Many dinnerware items from various origins that are sold on the open market were studied. Measurements of specific activities of 238U, 232Th, 40K and 137Cs radionuclide for the samples were carried out. The measurements were made by gamma-ray spectrometry having a high-purity germanium (HpGe) detector connected to a multichannel analyzer and a computer system. The average values of specific activities were (6.03 ± 0.54 to 223.67 ± 22.37 for 238U; 2.87 ± 0.14 to 513.85 ± 15.42 for 232Th; 28.67 ± 2.01 to 2726.70 ± 54.53 for 40K; and 0.592 ± 0.037 to 3.549 ± 0.248 for 137Cs) Bq kg−1, respectively. The glazed samples seemed to contribute most of the activity, although also unglazed samples showed some activity. The absorbed dose rates, radium equivalent and external hazard index were also calculated and tabulated. CR-39 solid-state nuclear track detectors were used to measure the radon track density, exhalation rate and effective radium content for the investigated samples. The exhalation rate was found to vary from 4.376 to 8.144 Bq m−2 d−1. It appears that foreign ceramic products, especially Chinese ones with high uranium content, eventually enter the country. The results from the two methods are compared and their combined uncertainties were estimated from the relation of relative combined variance. In Egypt, no special regulations exist concerning radioactivity in glazed earthenware. On the basis of the previous considerations, it appears that more specific regulations for dinnerware imports are necessary.