[ RadSafe ] Californium vs. Americium

[Doug Aitken]

There have been a number of geophysical logging tools that used straight Cf 
(SF) neutron sources, which were found to be more applicable to stimulating 
specific reactions due to their lower energy spectrum compared with 
alpha-Be sources, but the current interest is in using the Cf alphas due to 
the drying up of Americium supplies.

Unfortunately, even the best manufactured alpha-Be sources have relatively 
low efficiency/yield. So a material such as DU would not be practical....
Besides this, such a source would be a PR disaster, as WE KNOW that DU is 
the most dangerous substance on earth..........
;~)
Doug

At 01:37 PM 6/28/2007, Brennan, Mike  (DOH) wrote:
>I admit to not knowing much about these kinds of neutron sources (in my
>program, if you wanted to expose something to neutrons you ran it into
>the reactor), but I was under the impression that the reason for using
>CF was the SF neutrons.  My source says that CF-252 decays via SF about
>11% of the time.  I have no idea of what percentage of the alpha decays
>cause an "alpha + Be => n" reaction, but I suspect it is a function of
>the energy of the alpha and the abundance of Be atoms to encounter.
>
>I realize there are non-trivial drawbacks, but it is a shame that they
>can't use some of the DU to make DUBE sources.  In addition to a cool
>name, you could calibrate your logging equipment once, and you'd be good
>to go for your lifetime.
>
>-----Original Message-----
>From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
>Behalf Of Doug Aitken
>Sent: Thursday, June 28, 2007 10:08 AM
>To: Syd H. Levine; radsafe
>Subject: Re: [ RadSafe ] Californium vs. Americium
>
>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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Doug Aitken                     Office Phone Use Cell phone!
QHSE Advisor                    Home Phone 713 797-0919
D&M Operations Support  Cell Phone    713 562-8585
Schlumberger Technology Corporation