Measurements of Uranium, Radium and Radon exhalation rate in water and soil
Let employ CR-39 and following chemical etching to develop the alpha tracks due to the decay of U,Ra and Rn radionuclide. Furthermore, polycarbonate as another SSNTD may be used mostly with electrochemical etching to develop the alpha tracks accordingly. However, in this method the exhalation rate measurement is sluggish, usually needs high dose (flux * exposure time).
You are probably interested in measuring radon exhalation (or emanation) rates from rocks or soil. We are using both CR-39 and LR-115 in cups with crushed rock to measure Alpha tracks from 222Rn. These are slightly different SSNTD, and the availability and etching is different for each. As is widely done in this technique, we use a plastic barrier to impede diffusion, so we effectively remove decay from 220Rn, which has a very short half life. There is considerable literature on this technique. As Parviz notes, the exposure time is important, and we are exposing SSNTD above crushed granites and black shales for at least 3 months to get enough tracks. The measurements of uranium, thorium, radium need to be approached from different methods, but is likely that radon measurements are directly related to radium (but not necessarily uranium, nor thorium). Measurements can also be made using scintillation counting.
In addition to scintillation counting to measure fast, another rapid technique is developing based on laser induced breakdown spectroscopy (LIBS) and optical emission spectroscopy (OES). Regarding several chracteristic emmissions of radionuclides in laser induced plasma , the identification and quantification of trace elements are carried out as low as ppm level.
Dears/Dr. Barviz ; Dr . Garver; and Dr.Cotellessa thank you for your additions and useful contributions.
Best Regards
Dr. Abd Elmoniem Ahmed Elzain
It is very uncertain to employ SSNTDs in a combined measurement of Uranium and radium content i respect to radon exhalation. If the SSNTDs are left on the sample for a sufficient time (depends on the activity) the significant track-overlapping will occur. Try it in the ground ~ 50cm deep for a week just to check out. Moreover, SSNTDs ehxibit calibration errors, counting uncertainty and efficiency differentiation on the initial alpha energy. The latter renders different tracks sizes and brightness. Reported since 90's.
Better is to calibrate a High Purity Gamma detector or better faster and more efficient detectors (LSO, LYSO LGSO etc.). Employ proper Marineli beakers for that. Then, receive a certain grain sample, dry it, homogenize it and then count it in the detector assembly. This is a better solution, of much higher cost.
Thank you very much Dr. Dimitrios for your useful answer.
The best way to estimate uranium and radium in soils is by using gamma ray spectrometry using Low Level Counting using HPGe. Other geochemical methods could supplement the results so obtained. The amount of uranium and thorium present would depend on the soil type and presence of vegetation in the ambient environment. One the aforesaid estimates are obtained one could intercompare these results with radon exhalation using SSNTD's. The latter should time integrated based on the seasons in the area under study..
As I explained above , there are different methds with certain uncertainty:
1- SSNTD : recording the alpha tracks
2- Semiconductor : signals from alpha particle
3- Phoswich: detection of X - ray and Gamma emmision
4- HPGe: Gamma radiation
5- LIBS: Optical emmision spectroscopy of laser induced plasma
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