View source for Cf-252 FTC-CFZ-431

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=Overview=
An official document for the CF-252 source with serial number FTC-CFZ-431 provides a value for the neutron rate and CF-252 mass as of 03/19/1993. 

The initial neutron rate and mass of Cf-252 are stated to be <math>10^{7}s^{-1}</math> and 4.2<math>\mu g</math>, respectively. I am skeptical about the quoted neutron rate since 4.2 <math>\mu</math>g of pure Cf252 would not have a neutron rate that high. So, I did my calculations assuming that there was initially 4.2 <math>\mu</math>g of Cf with a isotopic composition that is typical for the date of production.

=Initial source composition=
Cf252 used in the US is produced in batches at Oak Ridge National Laboratory which all have similar isotopic make up. I found the isotopic composition of a batch produced in 1991, two years before the production date of our source<ref> http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-12-22883 </ref>. Assuming our source has the same isotopic composition as the 1991 batch and a total mass of 4.2 <math>\mu</math>g, the values in the following table can be calculated. Cf250 is of particular important since as the source becomes aged it will contribute significantly to neutron rate. 


{| border="2" 
!rowspan="3"| nuclide !! rowspan="3"| Atom % !! rowspan="3"|<math>T_{1/2}</math> [y] !! colspan="3" | as of 1993  
|-
!rowspan="2"| n atoms <math>*10^{15}</math>!! colspan="2" | decays <math>[s^{-1}]*10^3</math>
|-
!<math>\alpha</math>!! SF
|-
! <math>^{249}Cf</math>
| 5.76 || 351 || 0.58  ||36.0|| 0 
|-
! <math>^{250}Cf</math>
| 9.22 || 13.1 || 0.93 || 1,560 || 1.25
|-
! <math>^{251}Cf</math>
|2.85 || 898 || 0.29 || 7.02 ||0
|-
! <math>^{252}Cf</math>
|81.99 || 2.65 || 8.25 || 66,300 || 2120
|}

=Table of rates=
Click [[Cf-252 rates table|here]] to open a table giving neutron/alpha rates of the source for the next ten years.

=Formulas=

As the Cf252 source ages, neutrons from the SF of Cf250 become significant since it's has a half-life is 13 yrs, vs 2 yrs for CF252. Aside from Cf 252/250, there are no other significant neutron sources present.  

The formula used for neutron rate [<math>s^{-1}</math>]:

<math>\Delta t=\frac{(year-1993)+\frac{month-3}{12}}{2.645}</math>

<math>n_{0}rate=(r_{252})(3.7)(0.5)^{\frac{\Delta t}{t252_{1/2}}}+(r_{250})(3.5)(0.5)^{\frac{\Delta t}{t250_{1/2}}}</math>

where <math>r_{252}</math> and <math>r_{250}</math> are the initial SF rates of Cf252 and Cf250, respectively. 3.7 and 3.5 are the neutron multiplicities for Cf252 and Cf250, respectively.

=References=
<references/> 


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