Dear @paulromano
I’ve tried to tally k-eff in eigenvalue mode from my problem. The source generates from the bound box and distributed uniform. But from the result, I got k-eff only 0.66, which the expected result is 0.95. I would appreciate it if you could tell me what’s wrong with my script (I have sent it to you).
Here is my geometry
expect keff
Thanks in advance.
@billytnp Looking at your model, I see that for some of the materials, you haven’t assigned a density. For example,
target = openmc.Material()
target.add_element('Pb', 1.0, 'ao')
target.add_nuclide('Bi209', 1.0, 'ao')
When you don’t specify a density (with material.set_density(...)), it assumes that the atom fractions you specified are in units of atom/b-cm and it simply sums up what was given. In this case, that means target would have a density of 2 atom/b-cm, which works out to 691 g/cm³. You can confirm this yourself with target.get_mass_density(). The bottom line is you need to set the density to a reasonable value and that should hopefully get a k-effective value closer to what you expected.