Leakage as I know is the ratio of activity lost through glue or rubber and so on>>
= radon activity pass through material with out Bg/total Activity with out Bg?
is this true?
The problem is that you cannot calculate the activity transferred through the sample with high enough accuracy. The first question is what type of leakage are you interested in - leakage of the measurement apparatus or the joint apparatus-sample. For each of these you have to apply different procedures.
Kateřina Rovenská, many thanks, The problem is that i need high accuracy in measurements of radon diffusion coefficient, therefor i must calculate the leakage of the measurement apparatus and the joint apparatus-sample . I have complete system for radon diffusion i have rubber ring (need leakage calculation) and im using special glue for isolation (need leakage calculation) and finally sample.
Hello Mostafa
See this paper which came last July
Radon exhalation rates corrected for leakage and back diffusion – Evaluation of radon chambers and radon sources with application to ceramic tile
by M. Abo-Elmagd in Journal of Radiation Research and Applied Sciences
Good luck
small box (0.5 l) with Raduim source covered and isolated by sample in to radon cember 50 l. activity in chember measured with out sample (only source emanation) intial activity, and with sample to measure diffusion coeffeicent
Leakage is through loss of air from the sealed test system. Evacuate the system and observe the in-leakage rate. If you have no substantial change over the time of the planned experiment you will have negligible radon leakage. Pressurize the system and observe pressure changes. If there are no vacuum or pressure losses, there will be no leakage losses at normal temperature and pressure.
Diffusion through the seals can be tested by placing the radon source in the chamber and observing the final air concentration of the system. A measurable difference from the expected value indicates the loss. With this method you calibrate the chamber. The chamber calibration is the basis for comparing all measurements. There is no need to account for loss from the chamber if it is calibrated and sealing is reproducible.
A note on calculation of the diffusion constant. Several authors have introduced the term back diffusion. The diffusion equation describes a stochastic process. Atoms go in all directions in and out of the material. The diffusion constant accounts for 'back diffusion.' Inclusion of the term back diffusion is incorrect.
i think we need high accuracy for measurements the radon diffusion coefficient
- The leakage rate can be determined from the initial slope of the radon decay curve or from the exponential fitting of the whole decay curve. This can be achieved if a continuous monitoring of radon concentration inside the chamber is available. Also, the back diffusion rate is measured by sealing the radon source in the chamber and used the initial slope of the buildup curve to determine back diffusion and therefore the exhalation rate of the source. In such studies experiments should be carried out for long time so that we can easily evaluate the leakage rate as mentioned above.
You might find the answer for your question in the chapter 4.2.1. and/or the cited publications.
Or in this publication: Kis, Z., Völgyesi, P. & Szabó, Zs. (2013) DÖME - revitalizing a low-background counting chamber and developing a radon-tight sample holder for gamma-ray spectroscopy measurements. Journal of Radioanalytical and Nuclear Chemistry 298, 2029-2035.
You can find the formula you are looking for in the attached paper
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