Weird emission probabilities for discrete betas from Tc-99

Dear FLUKA experts

I’m running a relatively simple simulation consisting of a point source and a spherical surface for scoring with USRBDX. Apart from that, the geometry is completely empty (no air). The idea is to check the emission probability for different radionuclides.

By running Tc-99 (not Tc-99m) I found that there is something weird with the emission probabilities of the discrete betas. In most papers (e.g. Precision Measurements of Beta Spectra using Metallic Magnetic Calorimeters within the European Metrology Research Project MetroBeta | SpringerLink or Formfaktor des β-Spektrums von99Tc | SpringerLink) the discrete betas are practically not visible, because their probability is extremely low. But in my simulation, the peaks appear as the dominant emission for Tc-99.

In the attached figures you can compare the emission probabilites given by ENDF-B/VIII.0 and the ones I’m obtaining with FLUKA. The energies are correct, but the probabilities are a factor 1e6 times bigger in FLUKA for the discrete electrons.

What could be the reason for this discrepancy?

Please find attached the input file for your convenience.

Nuclide_Test.flair (2.7 KB)
Nuclide_Test.inp (1.7 KB)

Best regards,
Federico Geser

Dear FLUKA experts,

After searching for a while in the forum, I came across the following publication:

Probably this is exactly the problem I’m having. Could it be that Tc-99 was missed when this was corrected?

Thank you in advance for your help!

Hi Federico,

I have had a look at our decay radiation products database for 99Tc and can confirm that it contains too large branchings for Auger and XR associated with 99Tc decay.

We will correct the existing erroneous branchings for the upcoming minor release, however the 0.0016% secondary beta decay and corresponding gamma line are not present, and will not be added.

We are instead working on a major overhaul of the decay radiation database to solve all these little data issues, but that won’t be ready in the immediate future.

Best regards

Dear Philippe,

Thank you very much for your answer and for confirming the large branchings for Auger and XR from Tc-99.

I’m looking forward to the next minor release =)

Best regards,
Federico Geser