Measurement of indoor 222Rn using CR-39 under a thin film geometry

• Published in: Radiation measurements 2001-06, Vol.34 (1), p.145-148
• Main Authors: Neman, R.S, Schmitman, I.D, Hadler N, J.C, Iunes, P.J, Paulo, S.R, Guedes, S
• Format: Article
• Language: English
• Subjects: CR-39; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochronology; Isotope geochemistry. Geochronology; Measurement assembly; Pollution, environment geology; Radon
• ISSN: 1350-4487; 1879-0925
• DOI: 10.1016/S1350-4487(01)00140-8

In this work an assembly for indoor 222Rn measurement is presented. This assembly is made up of two acrylic plates (14 cm×14 cm) separated by a distance of 4 mm . To prevent radon daughters from outside entering the assembly (and produce alpha particle tracks striking the CR-39 detector placed in the central region of one of these plates), the borders of these plates were progressively closed, leaving open only a rectangular aperture of 5 mm×4 mm . The size of this opening was determined experimentally, by exposing in two indoor environments assemblies with different apertures as follows: (i) all borders open; (ii) two borders closed; (iii) three borders closed; (iv) four borders closed but one containing a 6 cm×4 mm opening; (v) four borders closed but one containing a 2.5 cm×4 mm opening and (vi) four borders closed but one containing a 0.5 cm×4 mm opening. Track density shows a noticeable decrease between assembly (i) and assembly (iii), remaining constant for smaller openings. Only 222Rn, a noble gas, should enter the assembly independently of the opening size.