Hi all，
I had a very strange problem with the triangular lattice calculation，the Flux_mps.png shows the flux maps of a triangular lattice contained Three identical fuel elements，One-sixth of each fuel element is located at a 60-degree Angle of an equilateral triangular lattice.
All three sides of the triangle use reflective boundary conditions
Theoretically, the flux distribution of these three fuel rods should be the same, but it is very strange that the flux of the fuel element rod at the top angle is higher than that of the other two. Can someone help me to answer it? Thank you very much.
@zhaozelong If everything is truly symmetric, as you said the flux should be the same in each of the three fuel elements. Do you have a model you can share that demonstrates what you are seeing?
Hi paul，
This is my python script for modeling and simulation. In recent days, I try to modify the input, I found that different spatial distribution of kcode source，different keff will be obtained，and the flux maps is still wrong.
Maybe this is due to that the neutron mean free path is equivalent to the geometric size, so the source distribution will affect the results？Thanks for the reply.
sca_4b_lat_b.py (13.2 KB)
This was also a bit puzzling to me until I realized that you have overlapping cells in your geometry model, which leads to the weird physical artifacts that you are seeing. Namely, this cell is defined incorrectly:
C99 = openmc.Cell(fill=M13, region=triangle_reg)
C99.region = C99.region & (+s5 | +s25 | +s35)
You should be using & in the region definition:
C99 = openmc.Cell(fill=M13, region=triangle_reg)
C99.region = C99.region & (+s5 & +s25 & +s35)
After that, running your problem gives a flat flux everywhere in the 2D mesh.
For future reference, the OpenMC user’s guide has some instructions about how to determine overlapping cells.
Thanks very much for solving and this puzzling problem，Paul. I will use the geometry check and debug function in the future modeling.
