[ RadSafe ] Californium vs. Americium

[Robert D Gallagher]

Am241 and Pu238Be both work fine in logging applications. World events have
made Pu a nono and Am241 is no longer available domestically. At the moment
all of the Am241 is coming from foreign sources. We are continuing to
attempt to get DOE to recycle Am241 from sources collected under the OSRP
program but have not yet accomplished that. It's really sad that thousands
of curies of Am-241 will be buried that could help solve the Am-241
shortfall.

Bob Gallagher
NSSI
713 641-0391

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl]On
Behalf Of Brennan, Mike (DOH)
Sent: Thursday, June 28, 2007 1:38 PM
To: radsafe
Subject: RE: [ RadSafe ] Californium vs. Americium


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

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