The national standard for 222Rn activity measurements developed at ENEA in Italy

In Italy, the Istituto Nazionale di Metrologia delle Radiazioni lonizzanti of ENEA, the Italian Primary Standard Institute for ionising radiation quantities, has developed a set of equipment to satisfy the national request of radon calibrations. These equipment are traceable to the ENEA national standard of 222Rn through an interrupted chain of transfer instruments. The 222Rn national standard is derived from the national standard of 226Ra and it is made by a 222Rn Reference Measurement System (RMS) and a 222Rn Transfer System (TS). The ENEA 222Rn standard has been compared with other 222Rn national standards in the frame of two EUROMET (European collaboration in measurement standards) intercomparisons carried out in 1992 and in 1994. The system of experimental equipment developed at ENEA and the relation to the national standard are reported. This paper briefly describes this system of experimental equipment. (author)