Correctly apply volumes to materials when using DAGMC geometries (#2787)

Co-authored-by: Nicolas Linden <n.linden@naarea.fr>

openmc/model/model.py

@@ -787,7 +787,12 @@ def calculate_volumes(self, threads=None, output=True, cwd='.',
                 for i, vol_calc in enumerate(self.settings.volume_calculations):
                     vol_calc.load_results(f"volume_{i + 1}.h5")
                     # First add them to the Python side
-                    self.geometry.add_volume_information(vol_calc)
+                    if vol_calc.domain_type == "material" and self.materials:
+                        for material in self.materials:
+                            if material.id in vol_calc.volumes:
+                                material.add_volume_information(vol_calc)
+                    else:
+                        self.geometry.add_volume_information(vol_calc)
 
                     # And now repeat for the C API
                     if self.is_initialized and vol_calc.domain_type == 'material':

openmc/summary.py

@@ -240,4 +240,9 @@ def add_volume_information(self, volume_calc):
             Results from a stochastic volume calculation
 
         """
-        self.geometry.add_volume_information(volume_calc)
+        if volume_calc.domain_type == "material" and self.materials:
+            for material in self.materials:
+                if material.id in volume_calc.volumes:
+                    material.add_volume_information(volume_calc)
+        else:
+            self.geometry.add_volume_information(volume_calc)