[OSM-talk] radioactivity

[Paul Houle]

John Smith wrote:
>
> The cost of a home made Geiger counter is about $100-200 in parts, and if you combine that with a gps logger you could log points combined with the rads, chances are you will end up with areas of the same values.
>   
      Cheap radiation measurement tools suck.  A homemade geiger counter 
is a fun experiment,  but I wouldn't count on it to be accurate at all.  
In fact,  expensive radiation counters aren't all that great either:  
the DHS has spent a lot of money on portal monitors and they really 
aren't as good as we'd like.

    Cheap counters are good at counting gamma particles,  but not so 
good at alpha particles,  betas or neutrons.  Specialized alpha counters 
exist,  but they need to be pressed right up to the thing you're 
counting.  If you don't get close enough to the radiation source,  
you'll miss it.  There's still controversy about the Harrisburg accident 
today,  since they didn't have instruments in the stack to measure beta 
radiation,  so we don't know exactly how much I131 went out the stack.

    There's a lot of practical interest in detecting Plutonium,  common 
isotopes of which emit alpha particles.  Workers exposed to Pu (such as 
Karen Silkwood) can have their exposure evaluated with whole-body gamma 
counters that detect gammas from Am241,  which is a decay product of 
Pu241.  The ratio of gamma rays to Pu all depends on the isotopic 
composition of the Pu,  how long it's been sitting around,  etc.  
Governments of the world would like to be able to detect smuggled Pu and 
assembled nuclear weapons with gamma ray counters,  but it's pretty 
tough to do.

    In the case of depleted U, which appears to have started this 
discussion,  it's not so clear what the actual hazard is.  U is 
pyrophoric and a bit toxic,  just as a chemical.  With a ~1Gy 
half-life,  most of the radiation from natural U comes from products in 
the decay chain (radium,  polonium,  etc.) and not from the actual U 
itself.  It's not exactly clear what the provenance of depleted U used 
in weapons it is:  some of it may be relatively clean,  but there could 
be dangerous contaminants in some of it.  There's also spotty evidence 
of chemical weapon involvement in some combat areas where DU has been 
used,  both in Iraq and Yugoslavia,  the governments of which had 
weaponized acetylcholine-targeting chemicals,  which can cause all sort 
of strange and lingering health problems.