Re: PuBe Sources - Increase in neutron flux

["Erik F. Shores" <eshores@LANL.GOV>]

At 06:31 PM 4/19/01 -0700, Ken Smith wrote:

>I was having difficulty understanding why this is.  Is the Pu-241 being

>generated by neutron absorption by the Pu-239 -> Pu-240 -> Pu241? Does

>this occur at an appreciable rate?  Or is the Pu-241 just a contaminate

>in the processing and isotope separation of the original PuBe source?

>Why does the presence of Pu-241 in a source increase the neutron output

>over time?  Is the increase in activity caused by the shorter half-life

>of Pu-241 (14 yr) and its daughter (Am-241, 433 yr.)? How far in the

>future will the output increase stabilize?



Hi Ken,



Mike is correct, Pu-241 is typically a contaminate in these types of 

sources. It beta decays to Am-241, which subsequently produces neutrons via 

its own alpha emission. Consider an initial Pu-241 content of 0.7%. The 

source's neutron yield would increase ~2% per year with a maximum yield in 

69.5 years (1.33 times the original yield). For additional information, see 

the following:



M.E. Anderson, "Increases in Neutron Yields of Plutonium-Beryllium (a,n) 

Sources," Nuclear Applications, 4,142-147 (1968).



Regards,

Erik



________________________________________

Erik F. Shores

Los Alamos National Laboratory

ESH-12, Radiological Engineering Team

Mailto:eshores@lanl.gov

505.665.7643 (phone)

505.667.9726 (facsimile) 



************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.

You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/