Re: sky shine?

[Ted de Castro <tdc@xrayted.com>]

First - throw away the "contact reading" - its meaningless - they
virtually always are!

I am not familiar with your nomenclature for the other reading.

Get a good reading at a distance from the source of more than 3 times
its greatest extent.

The skyshine will then depend on the solid angle subtended through the
open roof and simple calculations will only apply at 3 or more wall
heights away from the building.

The British Standards Institution produced a document - Data On
Shielding From Ionizing Radiation - B.S. 4094: Part 1 1966 - that makes
the calculations easy.  Surely its been updated by now - and it wasn't
easy to get!

I also recall a simplified - rule-of-thumb method that kinda almost
works.

I may have some specifics off - but it went something like:

Inverse square to a point about 2 meters above the roof and then inverse
square from there out to the point of interest THEN apply an appropriate
scatter factor for the air above the building.  I'd start with a
conservative factor of something like 10,000 as I recall.

It been YEARS since I did such a calculation - so I may have some of the
specifics wrong - but the quick method was something like that.

Surely SOMEONE out there will find it in their heart to correct any
errors I have made!

Need more accuracy - use a canned program!  The more you can tell it
about source and building geometries - the more accurate it can be.

Oh yeah - air attenuation (and build-up) counts.


mark sasser wrote:
> 
> An area shielded. say a bldg.  with an open roof,
> say with a dose rate of 200 MR/HR.contact on the
> object  maybe 80 MR/HR GA.how would sky shine come
> into play on clear days? or any day? this is for
> boundry set points. Barriers. ect.
> 
> =====
> mark sasser
> at duke99301@yahoo.com
> you can also reach me at duke9930@concentric.net
> 
> __________________________________________________
> Do You Yahoo!?
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