1st International comparison measurement on assessing the diffusion coefficient of radon

Abstract

Radon diffusion coefficient is a material parameter which is usually used in the radon mitigation measures design. There are different approaches used for radon diffusion coefficient measurement and assessment. The International comparison measurement which was jointly organised by National Radiation Protection Institute and Faculty of Civil Engineering CTU Prague in 2009 and 2010 has registered 11 laboratories from all over the world. Three sets of samples of polyethylene damp-proof membranes were sent to these laboratories for measurement. Till today, the organisers received only five sets of results. The results showed a great variability among laboratories involved.

Measurement of radon diffusion length in thin membranes

“…An improved experimental setup is expected to reduce them. A large spread of the measurement results from different groups was also reported in the international comparison exercise (11) .…”

“…The radon diffusion in thin membranes as part of an international comparison exercise organised by the National Radiation Protection Institute of Prague, who provided sample membranes to all the participants, was measured. The conference report (11) describes in detail, for each participant, the experimental procedure, the used equations for diffusion length (L) or diffusion coefficient (D) determination and the measurement results.…”

“…Our results were previously reported (12) . Table 1 shows the results for the three membrane densities and compares them with the results of the Czech group (11) . The first row shows our measured diffusion length L as a mean over six measurements together with the standard deviation.…”

“…The Czech measurements were also carried out by using radon diffusion from a source chamber, via the membrane, into a receiver chamber. The diffusion coefficient was determined by an iterative numerical solution of the diffusion equation (11) . Our results are in good agreement with those of the Czech group and with most of the reported results in the international exercise (11) .…”

“…With the typical effective volume of the charcoal of about 0.002 m 3 per gram (9) the effective volume of canister is about V AC ¼ 0.140 m 3 . From Eqs (10) and (11) it is estimated that 1 % of the radon emitted by the source will be in the air and 99 % will be in the canister. Formally, the charcoal 'enlarges' the geometrical volume of the chamber by its own effective volume.…”