Re: Radon

["Franz Schoenhofer" <franz.schoenhofer@CHELLO.AT>]

-----Ursprüngliche Nachricht-----

Von: Herbert Kouts <hjckouts@rcn.com>

An: radsafe@list.vanderbilt.edu <radsafe@list.vanderbilt.edu>

Datum: Montag, 18. Juni 2001 22:37

Betreff: Radon





>Studies at Oak Ridge a number of years ago revealed that the principal

>source of atmospheric radon  is plowing of agricultural land, which

>releases radon that has percolated into the soil.  Very likely this is

>the largest cause of radon exposure of the population at large.

>

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--



Dear Herbert,



I returned from my holidays recently, so my comment comes delayed, but since

the thread is still going on, it might not be too late.



You did not give the reference...... - can you give it? I do not believe,

what you stated and I have good reasons. There is no doubt, that ploughing

will enhance the radon emanation from soil, simply because the permeability

of the soil will be enhanced. Unlike in indoor air, you have wind over the

soil and the excess radon will within a very short time be diluted and

anyway it will decay with a physical half-life of 3.8 days. The only

persons, which will experience enhanced levels will be the men (or women)

sitting in the tractor and doing the ploughing. I do not know of any

research results, but common sense suggests, that the enhancement of

open-air radon might be a few percent of the average values of 5 to 15

Bq/m3. After a day on the field the worker might return home to sit in an

atmosphere containing a few hundreds or thousands of Bq/m3, but most

certainly with a concentration of 50 Bq/m3, which is approximately the

average in most European countries. The extra dose from ploughing might be

in the range of the uncertainity created by whether the windows are opened

or not.



The impact to the global population is actually zero, because the fraction

of the surface of the earth which is used for agriculture (not necessarily

ploughed!) is really negligible compared to the whole surface. Even more

ploughing is restricted to a very short time of the year and because of

different climate zones and latitudes distributed regionally and temporally.



Since the enhancement of radon concentrations on a global scale is more than

negligible there is no additional dose to the population - or in order to be

on the safe side - by orders of magnitude less than from indoor radon

exposure.



This is the first part of your message, which I respectfully disagree.



The second part I do not believe is the story about Sweden.



>I recall that some years ago the atmospheric sensors in Sweden were set

>off by radon released from the soil as snow cover melted in the north.

>For a time it was thought that atmospheric testing of nuclear weapons

>had been resumed, or that a large accident to a nuclear power plant had

>taken place.  I believe that this phenomenon is now anticipated and

>taken into account.



I have been in charge of the environmental radioactivity survey of Austria

for many years - but I admit not since about 10 years. I have maintained

close contact with the Swedish Radiation Protection Institute (SSI) ever

since, but I have never heard or read about such an incidence. The effect of

snow cover melted is a very well known phenomenon and not restricted to the

north of Sweden. I do not know of anybody, who would have been so silly in

Sweden, to assume that from (what???) data (dose rates?) atmospheric testing

had been resumed. Sweden has an excellent system for environmental

surveillance and I assure you that they know the difference between radon

and fission products!!!



Your mentioning of "a large nuclear accident" could give an explanation of

what you might be confusing. The data collected shortly after the Chernobyl

accident of a kind of gross-beta measurement system for aerosols in Finland

showed an enhancement of radioactivity. It is very well known, that dose

rates rise, when there is an inversion layer, because radon is not diluted

by winds and especially daughter products are accumulating in the air and

deposited on the ground, enhancing the dose rates measured. When this rise

was recorded in Finland it was first assumed that it might be the effect

from such inversion layers, which are quite common during the end of April,

beginning of May in Finland. But nuclide specific gamma-spectrometry showed

within short time, that the rise was due to fission products in the air.



You can easily prove that I am wrong by giving the references. Otherwise I

would encourage RADSAFErs, not to believe any stories, which use hearsay and

do not give the reference and the source of information. This appeal for

caution is both for anti- and pro-nuclear news, articles and comments.



Franz





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