not printing nuclides with 0 percent to terminal (option 2 ) (#3448)

Author: shimwell

openmc/deplete/stepresult.py

@@ -233,7 +233,7 @@ def get_material(self, mat_id):
             ) from e
         for nuc, _ in sorted(self.index_nuc.items(), key=lambda x: x[1]):
             atoms = self[0, mat_id, nuc]
-            if atoms < 0.0:
+            if atoms <= 0.0:
                 continue
             atom_per_bcm = atoms / vol * 1e-24
             material.add_nuclide(nuc, atom_per_bcm)

tests/unit_tests/test_deplete_resultslist.py

@@ -220,5 +220,4 @@ def test_stepresult_get_material(res):
     # Spot check number densities
     densities = mat1.get_nuclide_atom_densities()
     assert densities['Xe135'] == pytest.approx(1e-14)
-    assert densities['I135'] == pytest.approx(1e-21)
     assert densities['U234'] == pytest.approx(1.00506e-05)