"Volume not specified for material ID=2" even after assigning volume to mix material

User Support
1

Hello, everyone.

I am also facing the same problem but my problem is that I’m using mix_materials command. Here is a glimpse of my code:

Fuel Element [UO2 - 3.6 wt% U-235]

FE_Z36 = openmc.Material(name = “FE-Z36”, temperature = 1073 )
FE_Z36.add_nuclide(‘U235’, 0.036)
FE_Z36.add_nuclide(‘U238’, 0.964)
FE_Z36.add_nuclide(‘O16’, 2.0)
FE_Z36.set_density(‘g/cc’, 10.2)

Fuel Element [UO2 - 4.4 wt% U-235]

FE_Z44 = openmc.Material(name = “FE-Z44”, temperature = 1073 )
FE_Z44.add_nuclide(‘U235’, 0.044,‘wo’)
FE_Z44.add_nuclide(‘U238’, 0.956, ‘wo’)
FE_Z44.add_nuclide(‘O16’, 2.0, ‘wo’)
FE_Z44.set_density(‘g/cc’, 10.2)

Gadolina Gd2O3

GD = openmc.Material(name = “Gadolina”, temperature = 1073 )
GD.add_element(‘Gd’, 2.0,‘wo’)
GD.add_element(‘O’, 3.0, ‘wo’)
GD.set_density(‘g/cc’, 7.407)

Mixture [3.6wt% U235 and 5wt% Gd2O3]

FUG_Z36G5 = openmc.Material.mix_materials([FE_Z36, GD], [0.95, 0.05], ‘wo’)

As I am trying to deplete these materials in a hexagonal assembly, “Volume not specified for material ID=2” (FE_Z36) keeps on coming. I understand that its a depletable material but I am using it as a part of a mixture and I am defining “FUG_Z36G5” volume. If I define FE_Z36 volume as well, won’t there be an error in the result as the same material will be depleted twice?

I have seen the problem “Volume not specified for depletable material with ID=2 - #5 by hhhnain” but my problem is very much different than this one.

2

I tend to assign volumes to all the cells.

Then i fill the cells with any material, these can be single materials used on multiple cells or mixed made from other materials, but they should be depletable=True

Then i make the model and call this method on the model to make sure each cell has a single depletable material.

model.differentiate_depletable_mats(diff_volume_method=‘match cells’)

3

Thank you for your reply. So I should just assign volume to all depletable material and it should not affect my burnup results? As I have only used the mixed material in my geometry?

4

I would have thought that if you are only making use of FUG_Z36G5 then you would just need to set the volume for FUG_Z36G5.

5

Yes, I was doing so, thinking the same, however, openMC keeps on saying that all these materials need volume. I solved this issue by removing the mix material command and defining the mixed material with their atom densities directly. Although I’m not getting my desired Keff graph till now.

6

Are you able to share the full script