Migrated Amounts of Lead and Cadmium and Determination and Judgement on the Level of Upper Limit of Natural Radionuclides of Ceramic Bricks Produced by Somewhere in Sichuan Province

Sample of ceramic bricks were washed, dried and crashed to pass sieve with bore of 0.080 mm. A portion of 10.000 g of the minus sieve was heated in 25 mL of 50% (φ) HNO₃ solution on a hot plate at low temperature (ca. 200℃) for 2 h and the mixture was then removed from the hot plate and stayed at normal temperature for 1 h. The mixture was then filtered and the filtrate was diluted to 50.0 mL with water. This is the testing solution for determination of migrated lead and cadmium by ICP-AES with analytical spectral lines of 220.3 nm for lead, and 228.8 nm for cadmium. Another portion of the brick sample was pretreated in the same way but crashed to pass sieve with bore of 0.18 mm. And 500 g of the minus sieve were placed into a concave sample case and sealed for 7 d, after which the specific radioactivities of ²²⁶Ra, ²³²Th and ⁴⁰K were determined under the working conditions of the low-background multichannel γ-spectroscope and their indexes of internal and external exposure were calculated by the given formulas. As shown by the results of analysis of 30 samples taken from various batches, the amounts of cadmium migrated were found to be much lower than the limit value stipulated in the standard of HJ/T 297-2006 (i.e., not higher than 5 mg·kg^-1); however the amount of lead migrated in 2 of the 30 samples were found to be higher than the stipulated value (i.e., not higher than 20 mg·kg^-1), giving a qualification percentage of 93.3%. With reference to the national standard of GB 6566-2010, the results of levels of natural radionuclides found were all attained to the A class standard for decorating and fittingup materials.