MQCvisions

Information on the interpretation of RADMON data

The intensity of the radiation is indicated in nSv/h (nanosievert per hour).

For occupational exposure, the limit is 50 mSv in a single year with a maximum of 100 mSv in a consecutive five-year period, and for the public to an average of 1 mSv (0.001 Sv) of effective dose per year, not including medical and occupational exposures.
100 mSv mean 1.000.000.000 nSv, 100.000 hours of constant exposure to 250 nSv/h!
(a single radiography may expose to up to 700.000 nSv)

The natural average ambient dose rate is between 50 nSv/h and 250 nSv/h, depending on the local conditions.

(The radiation released by the Chernobyl nuclear accident in 1986 now contributes only a small part to the "natural" gamma ambient dose rate)

The external radiation exposure at any given place remains largely constant.

Increase due to snow and rain

Short-term increases up to a factor of 2 occur where radioactive decay products of radon, a natural radioactive noble gas, are washed out of the atmosphere by precipitation and are deposited on the ground.

These occurrences are almost always linked with precipitation.
It is typical for natural occurrences that the ambient dose rate increases for a short period of time and returns to its ordinary level within just a few hours.

The decrease of the ambient dose rate is usually asymptotic (the curve approaches the original level slowly) with a typical half-life period of 30 minutes; it occurs usually more slowly than the increase.

Snowfall may also lead to an increase of the ambient dose rate as in the case of rain, in particular if the ground was free of snow before.
After the ground is covered with snow, however, the ambient dose rate will remain on a lower level. The snow shields the terrestrial radiation effectively.
Once the snow begins to thaw, the ambient dose rate will return to its former level.

In addition to such short-term variations, the trend of the ambient dose rate is also subject to seasonal variations over longer periods of time that can amount to several 10 nSv/h.
The primary reason for this are constant changes in soil moisture, the geology of the ground, the surface properties of the ground and the microclimate on site.

CAUTION !

Please note that the hourly measured values published are unverified raw data that may not be free of technical interference.

Radiological incidents only give reason to worry if a significantly increased ambient dose rate is registered over a long period of time (e.g. one day or longer) or if the increase is more than two-fold and there is no reason to suspect a technical failure.

Temporary increases of the ambient dose rate caused by radon decay products being washed out of the atmosphere, as described above, cannot be considered as abnormalities.

Unusual values detected in the measuring system always have to be subject to an intensive plausibility check.