RE: NUMEC Pu-Be sources

[Richard_M_Pierson@RL.gov]

I have an old article written in 1967 by a M. Edward Anderson, Monsanto
Research Corporation.  We had a 40+ curie PuBe source on the NTS used for
neutron Quality Control dosimeter irradiation and the increases in neutron
yield due to Am-241 buildup were beginning to affect the results.  My
research turned up this article back in 1993.

Respond to me directly with your fax number and I can FAX the 5 pages.

The article establishes that an initial 0.7% Pu-241 impurity will result in
a yield increase of ~ 2% per year.  And the maximum yield will be ~ 1.33
times the original yield.  This maximum would be reached in 69.5 years.  It
also provides a table with plutonium isotopic abundance for some specific
source numbers.


Richard_M_Pierson@rl.gov
Richard M. Pierson, HP
River Protection Project
509.373.7591 Pgr. 85-3122


-----Original Message-----
From:	denison.8@osu.edu [SMTP:denison.8@osu.edu]
Sent:	Sunday, February 20, 2000 8:51 PM
To:	Multiple recipients of list
Subject:	NUMEC Pu-Be sources

Looking for information on the plutonium isotope composition of NUMEC Pu-Be
neutron sources.  The documentation I've found (including copies of old
reports to the AEC) lists the Pu-239 fraction, but says nothing about the
rest of the Pu mass.  I need to know the Pu-241 fraction in order to
calculate the increase in neutron production due to Am-241 ingrowth (see
note below).

I know that Babcock and Wilcox bought out NUMEC back in the 1970's, but I'm
not getting anywhere trying to contact them directly.  Their 800 number
referred me to the Lynchburg? Virginia facility, whose engineering
department forwarded me to their legal office, which hasn't called back.

I would appreciate any assistance you folks can give me in locating a
source for this information.  Thanks!

Eric

Note for those who haven't played with a Pu-Be source (lately):
Pu-241 beta decays with 14.4-yr half life to Am-241, and Am-241 alpha
decays with a half-life of 432 years and energies in the same range as
Pu-239.  Be captures alphas and emits neutrons, regardless of whether the
alphas come from Pu-239 or somewhere else.  Since Am-241 is longer-lived
than Pu-241, it builds to an equilibrium level, and since Am-241's decay
constant is 55 times greater than Pu-239's, the strength of the source
grows over time in proportion to the original Pu-241 fraction.  If all of
the "non-239" Pu in our source is Pu-241, the neutron output will be 4
times greater than if we have no Pu-241 at all.  Makes one hell of a
difference in my dose rate calculations!


J. Eric Denison
Nuclear Engineering Program
The Ohio State University
2030 Robinson Laboratory
206 West 18th Avenue
Columbus OH 43210
(614) 292-3681 or -1074
denison.8@osu.edu


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