Cf-252 FTC-CFZ-431
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]\displaystyle{ 10^{7}s^{-1} }[/math] and 4.2[math]\displaystyle{ \mu g }[/math], respectively.
4.2 [math]\displaystyle{ \mu g }[/math] would generate [math]\displaystyle{ 9.67 \times 10^{6} }[/math] neutrons per second. The discrepancy between these two numbers gives a 2% error.
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]\displaystyle{ \mu }[/math]g, the values in the following table can be calculated.
| nuclide | Atom % | [math]\displaystyle{ T_{1/2} }[/math] [y] | as of 1993 | ||
|---|---|---|---|---|---|
| n atoms [math]\displaystyle{ *10^{15} }[/math] | decays [math]\displaystyle{ [s^{-1}]*10^3 }[/math] | ||||
| [math]\displaystyle{ \alpha }[/math] | SF | ||||
| [math]\displaystyle{ ^{249}Cf }[/math] | 3.41 | 351 | 0.5612 | 63 | 0 |
| [math]\displaystyle{ ^{250}Cf }[/math] | 9.22 | 13.08 | 0.898 | 1,680 | 1.344 |
| [math]\displaystyle{ ^{251}Cf }[/math] | 2.85 | 898 | 0.278 | 23.7 | 0.759 |
Table of rates
Click here to open a table giving neutron rates and C-252 activity from dates 1/2017 to 12/2029. This calculation only includes neutrons from Cf-252, since all other daughter nuclei and possible impurities have a very low SF rate compared to Cf-252.
Formulas
Formula used for neutron rate [[math]\displaystyle{ s^{-1} }[/math]]:
[math]\displaystyle{ k=(0.5)^{\frac{(year-1993)+\frac{month-3}{12}}{2.645}} }[/math]
[math]\displaystyle{ n_{0}rate=9.835\times10^6\times k }[/math]
and for Cf-252 activity [[math]\displaystyle{ \mu Ci }[/math]]:
[math]\displaystyle{ activity=2283.3\times k }[/math]
References
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