NORMCONSTRUCT : results of the collaborative assessment experiment for the validation of the precision of CEN/TS 17216

Among the non-energy extractive industries in the EU, the construction minerals sector is the largest one. These minerals may contain enhanced levels of natural radioactivity. CEN/TS 17216 aims at providing a reference method for the determination of the activity of the radionuclides Ra-226, Th-232 and K-40 in construction products using semiconductor gamma-ray spectrometry. The method is developed by CEN/TC 351/WG 3 "Construction products: Assessment of release of dangerous substances Radiation from construction products" under Commission mandate M/366 which provides for the preparation of horizontal measurement/test methods in support of performance assessment of construction products (CE marking in the frame of the Construction Products Regulation, CPR). The precision of the method was evaluated with six construction products, analysed by 15 laboratories in a collaborative assessment. The reproducibility relative standard deviation for Ra-226 is 12.6 (5.4) %, for Th-232 it is 7.7 (3.2) % and for K-40 it is 8.3 (5.0) %. The bias of the method was re-assessed. The relative bias for Ra-226 is -7.5 (5.8) %, for Th-232 it is -1.4 (3.7) %, for K-40 it is 3.2 (2.4) %. All biases are insignificant at a 95 % confidence level. The bias for Ra-226 is the highest, but still insignificant caused by the higher reproducibility for Ra-226. The values for precision and bias are shown with their standard uncertainty in parentheses and apply within a limited validity range, specified in the report.