Problem with the decay chain of Pu-244 and the JEFF database

July 25th, 2017
by Joseph Magill

Qu.(from M.R. KTE Karlsruhe): We encountered a problem while reproducing the decay chain of Pu-244.
The first decay is an α-decay to U-240 followed by a β-decay to Np-240. The question is if U-240 decays to the metastable or directly to the ground state of Np-240. In the universal nuclide chart application in Nucleonica it shows a difference between the JEFF (Np-240) and ENDF (Np-240m) databases.
When using the Decay Engine++ application only the Np240 ground state is shown. The (more like a juristical) problem is that our regulations only include the metastable state.
Do you have additional information about the decay of U-240? Which one is the physical correct daughter?

Ans.(Nucleonica Team): Indeed there is an error in the JEFF3.1 database. You can also see this clearly in the KNCO application where you see that U-240 decays to Np-240m only. In view of this, we have changed the data in JEFF3.1 for U-240 – allowing only the decay to Np-240m. This you can see in the Nuclide Datasheets.
If you now redo the decay calculation for Pu-244, you will see the Np240m is much more important than Np240.
Thanks again for pointing this out and hopefully it did not cause to much inconvenience. It just shows once again how important it is to have a number of databases for comparison purposes.

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