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Warning Bug in Radioactive Decay? 

Forum: Hadronic Processes
Date: 09 Feb, 2017
From: Evan Rand <Evan Rand>

Hi G4 Experts, I donít know if you would call this a bug, but itís giving incorrect results. In particular, the production and lifetime of U-235. I found this ďbugĒ simulating the full decay chain of Pu-239. The alpha decay of Pu-239 feeds excited states in U-235. A large fraction of these alpha decays (and secondary gamma decays) feed a 0.077 keV meta-stable state in U-235. This state then decays to the ground state in U-235 via IT. Unfortunately, Geant4 does not do this. Geant4 will directly alpha decay from the 0.077 keV meta-stable state, and completely bypass the ground state. By doing this, Geant4 completely ignores the 7E+8 year half-life of U-235, and goes straight to Th-231.

It took me too long to figure this out, but it makes sense now. The 0.077 keV state in U-235 is very unique, as it is very low in energy (and longer lived). There must be an internal energy threshold in the radioactive decay process which assumes the energy of this state is so small, that it must be the ground state. Thus, the de-excitation process never gets a chance to decay this state. And by not populating the ground state, the half-life of U-235 is ignored.

Is it possible to lower this threshold (if it exists), so that the U-235 decay is treated correctly?

I am running Geant4.10.02.p02, with all standard data sets.

Thanks, Evan

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1 None: Re: Bug in Radioactive Decay?   (Nicole Ackerman - 28 Feb, 2017)
1 None: Re: Bug in Radioactive Decay?   (Evan - 28 Feb, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Fada Guan - 17 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Fada Guan - 18 Nov, 2017)
(_ Idea: Re: Bug in Radioactive Decay?   (Vladimir Ivanchenko - 19 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Fada Guan - 19 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (michel maire - 20 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Fada Guan - 20 Nov, 2017)
(_ Idea: Re: Bug in Radioactive Decay?   (Vladimir Ivanchenko - 20 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Fada Guan - 20 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Fada Guan - 20 Nov, 2017)
(_ None: Re: Bug in Radioactive Decay?   (Kyle Schmitt - 29 May, 2018)
2 None: Re: Bug in Radioactive Decay?   (Dennis H. Wright - 02 Mar, 2017)
3 Warning: Re: Bug in Radioactive Decay?   (Sasa Banjac - 23 Sep, 2018)
1 None: Re: Bug in Radioactive Decay?   (Sasa Banjac - 23 Sep, 2018)
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