Speaker
Description
Council Directive 2013/51/Euratom [1] requires considering any source of radon including the building materials. Measuring the radon exhalation rate from building materials samples is a useful “screening tool” to compare the likely contribution of building materials to the indoor radon. According to the current state of knowledge and technology, reliable values of radon exhalation rate from building materials sample are mainly achieved through the “dynamic method”, described by the IAEA Technical Report 474 [2]. The sample is enclosed in an accumulation chamber and radon concentration growth is monitored through a continuous radon monitor (CRM).
Most of the detectors used are not capable of distinguishing pulses produced by the interaction of alpha particles from radon and thoron progenies. The thoron interference may consequently lead to overestimate the radon exhalation rate.
Several measurements of radon exhalation rate have been carried out on samples of Italian tuffs characterized by high radium-226 and thorium-232 activity concentrations. The measurements have been performed with different experimental setups by varying the CRM, the ventilation inside the accumulation chamber, the position of the CRM and the radon-bearing air flow-rate inside the circulating loop.
The results will be presented focusing on the magnitude of the thoron interference on the estimation of the radon exhalation rate. Furthermore, the different experimental setups will be compared in terms of assessment accuracy and precision, time consumption, technical and economic feasibility.
References
1. European Commission, Council Directive 2013/59/Euratom: basic safety standards for protection against the dangers arising from exposure to ionising radiation, E. Commission, Editor. 2014, Official Journal of the European Union. p. 1-73.
2. Ishimori, Y., et al., Measurement and Calculation of Radon Releases from NORM Residues, in Technical Report 474. 2013, International Atomic Energy Agency (IAEA): Vienna.