Re: HVL-TVL OPINION

[rkathren@tricity.wsu.edu (ron kathren)]

That was precisely why the homogeneity coefficient (ratio of second to first
HVL) was developed.  

>Other than as a convenient concept for the
>classroom I THINK HVLs and TVLs are
>misleading at best for high energy gamma
>emitters.  The numerical value changes
>so drastically over the shield thicknesses
>normally encountered that use of some single
>standard value, even with the convention of
>adding an HVL for buildup, With the ready 
>availability of handheld or desktop computing
>shielding should simply be done directly.
>For example, for Co-60 and concrete ....
>  first TVL = 28+ cm2/g
>  second    = 19.7
>  third     = 17+
>  fourth    = 16+
>  seventh   = 15.6
>It takes a lot of TVLs to get to a 'constant'
>value.
>
>Admittedly, this is a somewhat extreme opinion,
>but any time I use a HVL or a TVL I find
>myself immediately doing a proper calculation.
>The only purpose the TVL serves is to reassure
>myself that I am not out in left field.
>
>P.S. That should stir up some hornets.  Send
>your stingers to me and I will compile a
>summary opinion.
>
>A little risk adds spice to life.
>slaback@MICF.NIST.gov
>
>