[ RadSafe ] Californium vs. Americium

[Doug Aitken]

Ahhhh. The Americium crunch....

AFAIK (and Bob of NSSI can confirm) the neutron yield of any "Xx"-Be source 
depends as much on the way you mix the two elements as it does the activity 
of your alpha source. But the mean neutron energy of a Cf-Be and Am-Be 
should be similar, given that this is the result of ejection of the neutron 
from the C13. Don't forget the small (lower energy) neutron yield from 
spontaneous fission of the Cf itself (~3% of the alpha production of the 
Cf) which, given the low efficiency of the Cf-Be neutron production, may 
change the overall energy spectrum vs an Am-Be source. and this may make 
any characterization of tool response based on Am-Be sources invalid....

But, as Bob of NSSI says,  the short half life, that forces a very frequent 
re-calibration of the logging equipment, and a short effective life of the 
source are probably the overriding reason that these sources are not often 
used.

(personal observations only: not in any way the opinion or recommendation 
of the company I consult for!)
Regards
Doug
At 10:47 AM 6/28/2007, Syd H. Levine wrote:
>Aside from half-life considerations, what are the technical issues with 
>using Californium in place of Americium in Be based neutron sources (for 
>well logging)?  Are the neutrons of the same energy?
>
>My understaning is the half-life is 2.64 years and that the well logging 
>sources are made up with about 30 Ci initially so that you wind up with 
>around 15 Ci at the end of that time period.  I am guessing one might be 
>able to log with them for five years maybe, then they could still be used 
>for tools that only need 3 Ci or so for awhile?
>
>TIA
>
>Syd H. Levine
>AnaLog Services, Inc.
>Phone:  (270) 276-5671
>Telefax:  (270) 276-5588
>E-mail:  analog at logwell.com
>Web URL:  www.logwell.com
>
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