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The paper presents the following problems which were solved during the deployment of the project: ·Elaboration of the radon standard concept: (i) design of the radon system: the radon generator source, the circuit for circulation, transfer, recovery ; (ii) choice of the standardization method; (iii) conception of an original traceability chain; (iv) definition of the basic requirements according to the international and national Norms regarding the monitoring and reporting of the radon concentration. ·Realization of the radon circuits, in two variants: (i) the preliminary one, from glass, used to demonstrate the feasibility of the system; (ii) the final, metallic variant, provided with the necessary gauges for the control of pressure level and of radon circulation and recovery. ·Elaboration of the method for the absolute standardization of the equilibrium radon decay chain, by liquid scintillation counting (LSC). ·Realization of various types of recipients, with radon as gas and dissolved/adsorbed in liquid scintillator, and their measurement by HPGe gamma-ray spectrometry, ionisation chamber and LSC. Elaboration of a computing model for radon circulation in various matrices: soil, water and active charcoal. ·Establishment of the traceability chain, from the primary standard to the calibrated secondary equipments and preparation of radon recipients with the radon activity certified. ·Study of the LS efficiency influence on the radon measurement. [ABSTRACT FROM AUTHOR]