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AW: temporal? variations in background

-----Ursprüngliche Nachricht-----

Von: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu]Im Auftrag von Kai Kaletsch

Gesendet: Sonntag, 08. September 2002 02:12

An: Ted de Castro

Cc: radsafe

Betreff: Re: temporal? variations in background


I was talking about radon, not gamma. Radon gets displaced from the pore

spaces in the soil by the water and gets into the air and into your house.


This is wrong. When rain pours onto the open soil, there is no possibility

for radon and its progeny to emanate to the air, since rain closes all

pores. Environmental emanation is therefore decreased, but emenation into

dry places like a house is clearly enhanced.


The displacement of radon gas is probably part of the reason gamma goes

down. Remember, 95% of the gamma radiation from the U decay series comes

from the short lived radon progeny, Bi-214 and Pb-214. Water would also add

a bit to the shielding. Radon would take a few days to grow back in after

the soil has dried. Do you notice a lag like that in your gamma readings?


Again wrong. There is clearly an enhancement of terrestrial gamma dose rate

in the course of a rain fall. The reason is simple: Radon progeny is washed

out by rain and is deposited onto the ground, causing an enhanced

gamma-radiation doserate. This is more than well known since about 50 years

from automatic and other surveillance systems. At least in Europe we have

them and the data can be even monitored by the public on the so-called

"teletext" on TV, which might not be standard in the USA. This small

enhancement poses some problems for the surveillance systems, because

sometimes the alarming levels might be exceeded by this natural phenomenon.



> Kai Kaletsch wrote:

> >

> > While the discussion on variation in BG is going on: Does anyone have an

> > idea of the variations in BG radiation over time? There are short term

> > spikes in radon after a rain and there are changes in cosmic ray fluxes


> > How do these phenomena affect the long term average exposure?


They are negligible - please calculate them yourself if you do not believe



> >

> > For example, if my radiation exposure last year was 3.0 mSv and I live


> > the same place and do the same things this year, how close to 3.0 mSv

can I

> > expect my exposure to be this year?

> >


Your exposure cannot be 3.0 mSv, it has to have an error, which means, that

it might be 3.0 +- 1.0 mSv. I expect that your next-year exposure would be

within your error. Have you undergone any x-ray diagnostic, have you climed

a mountain, have you had a nuclear medicine diagnosis? You do not state,

what you call "background". Does it include medical exposure, does it

include exposure to articial radionuclides dispersed into the environment?


> > How do these temporal variations in natural BG compare with events such


> > atmospheric weapons testing, Chernobyl etc...?

> >


Do you really expect that you will receive by RADSAFE detailed information

about both atmospheric testing and Chernobyl effects? They would fill many

volumes of scientific textbooks. But an extremely short "course":

Atmospheric testing caused additional radiation doses to a lot of people,

mostly in the Northern Hemisphere. Marshall Islands have a different

approach. Doses were mostly caused by internal uptake of contaminated food,

less by inhalation and less by gamma-radiation from the ground and extremely

different as to geographic conditions. There is a tremendous amount of

literature on this, which I recommend you to consult, if you are really

interested - but be careful, it would probably take you several years to

study all of that. The Chernobyl effect was more or less exclusively limited

to the vicinity, eastern and middle Europe, with some areas like Cumbria

outside this area. Again I recommend you to read the literature and again I

expect that you will need a few years to get through of that. There are no

"summaries", and be careful of any "mean" values distributed by some

agencies. The most difficult problem is, that the values of contamination

are different by some orders of magnitude for different areas within the

same country.

Would you please

So, if you want to have some information about the topics you asked for,

please "refine your search", because otherwise you would not receive much

responses, at least no relevant ones.

Best regards,



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