A new passive radon-thoron discriminative measurement system

Abstract

A new passive radon-thoron discriminative measurement system has been developed for monitoring radon and thoron individually. It consists of a 'couple' of passive integrating devices with a CR39 nuclear track detector (NTD). The experimental prototype is based on the application of a new concept of NTD instrument developed at ENEA, named Alpha-PREM, acronym of piston radon exposure meter, which allows controlling the detector exposure with a patented sampling technique (Int. Eu. Pat. and US Pat.). The 'twin diffusion chambers system' was based on two A-PREM devices consisting of the standard device, named NTD-Rn, and a modified version, named NTD-Rn/Tn, which was set up to improve thoron sampling efficiency of the diffusion chamber, without changing the geometry and the start/stop function of the NTD-Rn device. Coupling devices fitted on each device allowed getting a system, which works as a double-chamber structure when deployed at the monitoring position. In this paper both technical and physical aspects are considered.

Study of variation of 222Rn/220Rn and their progeny concentration in dwellings using single entry pin hole-based diffusion chambers

“…12,13 However, the method still lacked in discriminating 222 Rn and 220 Rn and this was overcome by introducing a twin chamber devise with a diffusion barrier to cut off 220 Rn transmission either by a membrane- 14,15 or pinhole-based diffusion barriers. 16 However, this device reported physically unacceptable negative 220 Rn concentrations. The possible reason for this is different entry rates of 222 Rn through two entrances arising from turbulence or air flow and this has been ensured experimentally and eliminating all discrepancies with a requirement of cellophane membrane.…”

Characteristics of Thoron (220Rn) and Its Progeny in the Indoor Environment

“…A pin-hole based 222 Rn/ 220 Rn discriminator was installed in the monitor. For discriminative measurement of two radon isotopes, a pin-hole diffusion barrier was used [ 24 , 25 ]. This is because different entry rates of 222 Rn were pointed out through two entrances of the dosimeter which might arise from turbulence or air flow in one direction.…”

An Improved Passive CR-39-Based Direct 222Rn/220Rn Progeny Detector

“…The Model 3034 SMPS TM Scanning Mobility Particle Sizer produced by TSI ® was adopted to measure the concentration of condensation nuclei, CMD, and its GSD (σ g ). The concentration of condensation nuclei in the exposure chamber ranged from 2.05 × 10 4 to 4.32 × 10 4 particles per cm 3 . The CMD of the aerosol in the exposure chamber ranged from 0.187 to 0.218 µm.…”

“…In the conventional integrating measurements for 222 Rn and 220 Rn activity concentrations in a large-scale survey, the solid-state nuclear track detector (SSNTD) technique is usually used. Several designs of measuring devices using SSNTD have been used for indoor 222 Rn and 220 Rn surveys, such as RADUET [1], Pin-hole dosimeter [2][3][4], and so on. In the two different diffusion rate chambers of these measuring devices, because there is a diffusion barrier against 220 Rn based on its quite short half-life, the low diffusion rate chamber detects mainly 222 Rn and the high diffusion rate chamber detects both 222 Rn and 220 Rn.…”