Nested RectLattice

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1

I am trying to use nested Rectangular Lattices to create the geometry.

Testing works for individual pins and assemblies for each assembly type in a single (un-nested) lattice with no particles getting lost and expected values for k_eff.

When testing as a nested lattice - notebook here - particles are immediately lost as they cross the fuel pellet surface.

I sense there is an issue with how I am using the “outer” universe for the nested lattice but maybe there is something else more subtle (or more obvious!) that I am missing.

Any help or suggestions are very much appreciated.

Best Regards,
Stu

2

@stu646 I believe the problem in your model is that you are trying to add the same cell(s) to multiple universes:

fpc.add_cells([fuel_cell,gap_cell,clad_cell,coolant_cell])
...
bpc.add_cells([blanket_cell,gap_cell,clad_cell,
              coolant_cell]);

Cells can only belong to a single universe, so when you add gap_cell and others to a second universe (bpc), they no longer exist in the first (fpc). This is why you are seeing lost particles.

EDIT: I should have also mentioned that in our documentation, there is some guidance on how to diagnose issues with lost particles.

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3

head slap

Thank you very much for the quick reply and thank you for noting the guidance from your documentation.

I do not want to admit the rationalizations I was making when typing the Python code celebrating the possibility of not having to re-define “redundant” cells; in retrospect the problem should have been obvious from reading the geometry.xml file.

Thank you, again, and have a great day.

Best Regards,
Stu

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