Re: temporal? variations in background

[JGinniver@AOL.COM]

In a message dated 08/09/02 20:58:14 GMT Daylight Time, info@eic.nu writes:



> I was interested in the Chernobyl effects on Scotland and Wales. Somewhere,
>
> I saw a value of 0.1 mSv from Chernobyl. So to make my question more
>
> specific: 1    Can someone confirm the 0.1 mSv value?
>
> 2    How does 0.1 mSv compare to the variations in year over year average
>
> dose for the populations of Scotland and Wales?
>
>
> I'll also take any other tidbits of information such as doses from weapons
>
> testing fallout on the US during the testing years.



Having looked in "Ionising Radiation Exposure of the UK population: 1999 Review - NRPB-R311" published unsurprisingly by the National Radiological Protection Board in the UK, it would appear that the 0.1 mSv value would be be recived by idividuals eating 8 kg/y of sheepmeat at the EC limit for foodstuffs of 1000 Bq/kg.  I don't have specific values for the period immediately after the Chornobyl accident, but the estimates of the NRPB for the "average annual dose in high deposition areas of the UK  in the mid-1990s was estimated to be approximately 10 microSv: that is about twice the UK average."


This compares with "the average annual dose in the UK from all sources is  2,600 microSv."  About 85% (2,200 microSv) is from natural sources.  The highest average annual dose, 7,800 microSv, is found in Cornwall, but those for most counties in the UK are within about 30% of the UK average.


The last section of the above may go some way to answering the original question, but for the UK rather than the US.  The temporal variation from natural background being about 30% across most of the UK.  However an individuals exposure to natural radiation can be affected by a number of factors.  E.g. the elevated levels of indoor radon in Cornwall would result in an additional 200 microSv (almost 10% of the national average for natural exposure) being recieved during a 2 week stay in the area.

Eating a bag of Brazil nuts or a jar of mussels each week would result in a similar increase.  A frequent flier aloft in a jet aircraft for about 100 hours a year would recieve approximately 400 microSv (20% of the average annual exposure in the UK to natural radiation).  All of this information was obtained from NRPB-R311.


I hope the above helps.


Regards

       Julian