Decay Engine – Daughter activities zero?

June 23rd, 2020
by Joseph Magill

Qu.) PB, CERN, Switzerland
Dear Nucleonica Team,
I wanted to make a quick test to validate a part of a code one colleague developed, by decaying 1 Bq of Fm-257 during 1 second. please find below the result:
Fm257 Decay We were surprised to see that for many daughter radionuclide, activity calculated is zero. We found on our side very low activities (1.192E-6 for Cf-253 / 8.818E-13 for Cm-249 / 6.172E-13 for Es-253 / <1E-18 for the other).

I was wondering if you applied like a cut of, meaning if the activity is below a certain value, you show 0? If yes, what is this cut off?

(Ans. Nucleonica Team)
We do indeed we apply a threshold: when the number of atoms for a nuclide is less than 0.5 and also if its activity is less than 1% from the total activity the number of atoms for this nuclide is set to 0. In the Decay Tree tab (a section is shown below) the cut off is not applied so you can see the calculated number of atoms.
DecayTree-Fm257 To avoid the problem of zero activites, you have always the possibility to use a higher starting quantity e.g. 1 GBq or 1 Tbq. We are currently considering suppressing the cut-off, in which case the results in the main tab will be similar to those in the Decay Tree tab.

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