Error while using 218Po isotope source

Source Definition
1

Dear Fluka experts,
I want to generate radiation from 218Po and all its daughters. From what I’ve read, I understand that by using sdum=ISOTOPE in BEAM card and semi-analogue decay mode it is possible to generate beta and gamma radiation, but not alpha radiation. That would be fine for me (as I can simulate the alpha radiation separately), however when I set

HI-PROPE 84 218

I get the following error messages in the Output
Error code: 12
and in the .log file
STOP Exceeded upper dp/dx abscissa.
Note: The following floating-point exceptions are signalling: IEEE_UNDERFLOW_FLAG IEEE_DENORMAL
STOP STOP: FLUKA ABORTED

I also tried radionuclides 226Ra, 214Pb, 214Bi and 241Am with the same result. But with radionuclides undergoing the beta decay (131I, 60Co) the simulation runs and ends well.

Where could be a problem?

I have Fluka version 4.2.0. I attach the input and the generated files.

vstup.flair (4.0 KB)
vstup.inp (2.4 KB)
vstup.out (768 Bytes)
vstup001.err (604 Bytes)
vstup001.log (158 Bytes)
vstup001.out (76.8 KB)

3

Dear Michal,

not really, with FLUKA 4.2 you now get the alpha radiation too (as indicated in the release notes) … and this is actually the reason of the crash you undergo: in the (logical) absence of the BEAM energy, the upper limit of the stopping power tabulation for the alpha transport turns out to be inadequate for the 5 MeV alpha emitted by 218Po (analogously for the other decay chains implying alpha emitters).
This is a bug, whose fix is going to further enrich the 4.2.1 minor release planned for next month.
In the meantime, you can bypass the issue by setting a high transport threshold for 4-HELIUM with PART-THR.
Thanks for reporting!

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