My juniors are working on Natural Background Radiation monitoring. They used GCA-07 GM Counter for the measurement of Natural Background Radiation at different places of Kathmandu city. From the data records, I found a little bit larger dose rate at heights (three sampling area was chosen and found consistent results), and areas containing dense vegetation (three different sampling area was taken and found quite similar results). What could be the possible reasons, that can be addressed, behind this bit larger dose rate than in normal areas?
Dear Sujan Prasad Gautam ,
two suggestions:
Height dependence:
What height difference you are talking about?
You are 'a bit' closer to space. So due to the lack of 'a bit' of atmoshere there is 'a bit' less attenuation of cosmic radiation...
Vegetation: Among other elements, Potassium (K) is picked up by vegetation; K40 is radioactive....
You should perform a spectral investigation on gamma photon energy distribution.
K40 emits gammas at 1,46MeV; see for example:
https://en.wikipedia.org/wiki/Potassium-40
Dear Dr. Gerhard Martens
Thank you very much for your valuable suggestions.
:)
Dear Sujan Prasad Gautam,
Recently, the health risk of aircrews has become an issue due to the fact that the higher the altitude, the greater the exposure to cosmic rays. As the altitude increases, the thickness of the atmosphere decreases and the exposure to radiation from space (cosmic rays) increases.
At the height of 10 to 12 km, where commercial aircraft fly, the dose of cosmic rays is almost a hundred times higher than on level ground. The main components of cosmic rays that we are exposed to while flying are secondary particles, such as neutrons, protons, electrons, photons, pions, muons, etc., which are avalanches of high-energy particles from our galaxy and other galaxies that collide with atmospheric atoms. Of these, neutrons contribute the most to exposure in the sky, and are estimated to account for about half of the effective dose. (Near the ground, it is mainly by muons.)
A round-trip flight between Asia and Europe will result in an exposure dose of about 0.1 mSv. This is not a big problem for an occasional passenger, but for a daily crew member, an accumulation of 3-4 mSv/year can be expected.
Please see the attached file if you are interested in this problem.
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