Keff indiscrepency when modelling TRISO fuel particles

Validation and Verification
1

Hello,

I’m modelling TRISO fuel particles in a box (1cmx1cmx1cm). I have taken the example from this post Simulation Triso - #2 by mkreher13. I ran the example first and got kinf ~ 1.06. I have then changed the material compositions and TRISO particle radii for the specific problem I am modelling. The kinf for this problem is ~0.69. Given that the problem is a box with reflective BC I would expect the kinf > 1. All that I have changed from the example is the material compositions and particle radii so I don’t understand this result. I have modelled the same problem in Serpent and got kinf~1.38 which is what I would expect from this problem. I have attached my file.
triso_box_v2.py (3.4 KB)

Best wishes,

Emma

1 Like
2

Hi,
If you are getting different results between OpenMC and Serpent after changing the material composition and the particle radii, I suggest you check the units. Firstly, ensure that you obtain the same result between OpenMC and Serpent for the original problem with kinf=1.06. If you don’t obtain the same result, that may be due to a unit discrepency between the two codes or a low number of neutrons simulated. Once you get those to agree, try your changes again. Ensure that the material composition units (densities versus atomic percentages) are the same in both codes and that the particle radii use the same units (centimeters versus meters for example).