Unknown peaks in U-234 alpha spectrum

Dear experts

As U-234 undergoes 100% alpha decays with alpha energies upto 4.774 MeV, then what are these two peaks at energy 5.3 and 5.5 MeV in its alpha spectrum?

I have used ISOTOPE card with HI-PROP card to define U234 with semi-analogue in RADDECAY.

Test.flair (3.1 KB)
NNDC_U234.pdf (31.0 KB)

1 Like

Dear @rohityadav,

You are also seeing the alpha particles emitted by the secondaries in the decay chain. If you increase the Emax in USRBDX card you can see alpha particles emitted with energies up to 7.686 MeV (corresponding to Po-216).


Indeed, the line at 5.5 MeV (5.489 MeV) comes from the Rn-222 → Po-218.


Dear Rohit Yadav

Kindly informed that; these peaks are well know and are attributed to several daughter nuclei. The 5.32 MeV related to U-232 and the 5.5 MeV belongs to some others as shown in the The decay chain of uranium-238 sited in


also from the Alpha Particle Energies table sited in

you can easily identify the origin of these peaks and can modify the fluka input file according this appearance.
Best Regards

1 Like

A post was split to a new topic: Resolution of USRBDX particle spectra

Hi Rohit Yadav
I found in the Table of Isotopes the energy and Intensities of others related alphas. 2 strong 4.722 and 4.774 MeV and 3 weak 4.1, 4.2 amd 4.6 MeV. I suggest you can search for it in the *tab.lis output file. From this you will see the goodness and sensitivity of FLUKA to produce this low weak alphas.
For this you can adjust E min and E max at 4100-4780 keV using a good bin value to reach a good comparison.


1 Like

A post was split to a new topic: Filtering daughter nuclides in decay chain