Simulation of depleted uranium shielding in gamma spectrometry

Dear Fluka experts,

I apologise if I’m writing in the wrong category or about an existing topic.

I’m using Fluka to simulate radioactive sources with different shieldings.
In this particular case (Uranium shielding) I have a 137Cs source in an uranium contenitor.
When trying to set-up a depleted uranium shield Fluka gives errors
without specifying which type of error it is.
I suppose the problem is that the shield is an emitter too.
Do you know if there is a way to bypass the problem
or is it because I made any kind of mistake when writing the input?

Sorry again, this is my first topic in the forum
Thank you in advance for your answers.
Uranium_shielding.flair (3.0 KB)
Uranium_shielding.inp (2.7 KB)


I solved with the LOW-MAT card, the problem was in the cross section of low energy neutrons.

Please note that your geometry has errors. Look in flair geometry tab