ISO 16641:2014 pdf free
ISO 16641:2014 pdf free.Measurement of radioactivity in the environment
The integrated measurement of the average radon 220 activity concentration using a solid-state nuclear track detector (SSNTD) is based on the following:[12]
一passive sampling using two chambers with different air-exchange rates during which the alpha particles, including those produced by the disintegration of radon-220, radon-222, and their decay products, transfer their energy by ionizing or exciting the atoms in the polymer or plastic. This energy transferred to the medium leaves areas of damage called “latent tracks”. Because of their different half-lives, radon-222 and radon-220 can be separated using these two chambers. In the high air-exchange rate chamber, both isotopes are detected. In the low air-exchange rate chamber, however, radon-222 is mainly detected with only a small quantity of radon-220 (see Figure 1);
The high air-exchange rate should be set as high as possible so that the calibration factor of radon-20 is ideally the same as that of radon-222. On the contrary, the low air-exchange rate should be set as low as possible with a high diffusion barrier.
一transport of the exposed detectors to the laboratory for the appropriate chemical processing which transforms the latent tracks into “visible tracks” counted via an optical system. The number of these visible tracks per unit surface area is linked to the exposure value of the radon-220 and its decay products by the calibration factor defined for detectors in the same batch processed chemically and counted under the same conditions;
一determination of the radon-220 average activity concentration from the exposure value of both chambers and the sampling period.
Each of them is associated with a solid state nuclear track detector. Each closed accumulation chamber has a filter through which the radon-220 and radon-222 diffuse. This filter is set to prevent access of the aerosols present in the air at the time of sampling, especially the solid radon-220 and radon-222 decay
products (see Figure 2).
The SSNTD shall come from the same sheet of plastic to avoid different results. Nevertheless each SSNTD batch is calibrated.ISO 16641 pdf download.
