Task 2.3: Development of techniques to reduce the influence of thoron on radon measurements and calibrations

The aim of this task is to develop techniques to reduce the influence of thoron on radon measurements and calibrations. Task 2.2 will investigate and develop a better understanding of the influence of thoron on radon measurements to potentially correct for this effect, whereas this task will develop practical techniques to reduce the influence of the thoron on radon measurements.
A literature review of potential methods to reduce the influence of thoron will be performed and systematic analysis of the different methods undertaken by STUK and SUBG. The properties of different filters/foils/membranes that might serve as selective thoron barriers (whilst not reducing radon penetration significantly) will be studied by SUBG and CEA. Recommendations will be proposed by SUBG, BEV-PTP, CEA, STUK and IRSN about the construction of radon monitors that are not sensitive to thoron and solutions aimed at reducing thoron-related bias in the radon signal in existing monitors (e.g. by using packaging/envelope as a thoron-barrier). Procedures to check the radon monitors for sensitivity to thoron will also be proposed.