Re: Risk with Am241/Be source? - Addendum

[LIPTONW@detroitedison.com]

You wrote: 
 
>Date: Sun, 10 May 1998 13:50:24 -0500 (CDT) 
>From: "Björn Cedervall" <bjorn_cedervall@hotmail.com> 
>To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu> 
>Subject: Risk with Am241/Be source? 
> 
>Radsafers, 
> 
>A friend of mine recently asked about the potential radiation risks  
with  
>Americium (241)-Beryllium neutron generators. The probe device is used  
>for measuring moisture and density in soil etc. The probe contains 30  
>mCi 241-Am/Beryllium (the half-life of 241-Am is about 458 y) as well  
as  
>1 mCi cesium 137. The neutron yield can probably be taken as (??)  
>2.5x10E6 neutrons/(second,Ci). 
> 
> 
> 
>The question is what the radiation exposure (neutrons and gamma, what  
>would the energies of the neutrons and gamma components be?, weighted  
>whole body mSv/h?) whould amount to if the probe is taken out of its  
>protective shield (which I understand has to be done in order to  
perform  
>certain types of calibration measurements). Reasonable assumptions are  
>that the person in question - "the point target?" will stand 1 meter  
(m)  
>from the probe which can be considered as a point source. 
> 
> 
> 
>Many thanks in advance, 
> 
> 
> 
>Bjorn Cedervall, 
> 
>PhD (Karolinska Institutet) 
 
A good source of information i Amersham/Searle Technical bulletin 76/7, 
"Neutron Sources:  Americium/Beryllium and Californium-252".  This may not
be 
available any more.  Here is some data for a Am-241/Be source: 
 
neutron emission:  2.2 E6 neutrons/sec-Ci 
 
Fraction of neutrons below 1.5 Mev:  ~ 0.23 
 
gamma emission per neutron:  0.7 at 4.43 MeV, from (alpha-n) reacton, plus 
6000 from Am-241 decay, predominantly at 60 keV 
 
neutron dose equivalent rate at 1 m for source emission of 1 E6
neutrons/sec:  
~ 1 mrem/h  (It's not clear what Q is used.) 
 
gamma exposure rate at 1 m for source emission of 1 E6 neutrons/sec:  ~ 1
mR/h 
 
The opinions expressed are strictly mine. 
It's not about dose, it's about trust. 
 
Bill Lipton 
liptonw@detroitedison.com