Custom densities

armi/reactor/blueprints/componentBlueprint.py

@@ -225,8 +225,66 @@ class can then use to modify the isotopics as necessary.
             constructedObject = components.factory(shape, [], kwargs)
             _setComponentFlags(constructedObject, self.flags, blueprint)
             insertDepletableNuclideKeys(constructedObject, blueprint)
+
+        # set the custom density for non-custom material components after construction
+        self.setCustomDensity(constructedObject, blueprint, matMods)
+
         return constructedObject
 
+    def setCustomDensity(self, constructedComponent, blueprint, matMods):
+        """Apply a custom density to a material with custom isotopics but not a 'custom material'."""
+        if self.isotopics is None:
+            # No custom isotopics specified
+            return
+
+        density = blueprint.customIsotopics[self.isotopics].density
+        if density is None:
+            # Nothing to do
+            return
+
+        if density <= 0:
+            runLog.error(
+                "A zero or negative density was specified in a custom isotopics input. "
+                "This is not permitted, if a 0 density material is needed, use 'Void'. "
+                "The component is {} and the isotopics entry is {}.".format(
+                    constructedComponent, self.isotopics
+                )
+            )
+            raise ValueError(
+                "A zero or negative density was specified in the custom isotopics for a component"
+            )
+
+        mat = materials.resolveMaterialClassByName(self.material)()
+        if not isinstance(mat, materials.Custom):
+            # check for some problem cases
+            if "TD_frac" in matMods.keys():
+                runLog.warning(
+                    "Both TD_frac and a custom density (custom isotopics) has been specified for "
+                    "material {}. The custom density will override the density calculated using "
+                    "TD_frac.".format(self.material)
+                )
+            if not mat.density(Tc=self.Tinput) > 0:
+                runLog.error(
+                    "A custom density has been assigned to material '{}', which has no baseline "
+                    "density. Only materials with a starting density may be assigned a density. "
+                    "This comes up e.g. if isotopics are assigned to 'Void'.".format(
+                        self.material
+                    )
+                )
+                raise ValueError(
+                    "Cannot apply custom densities to materials without density."
+                )
+
+            densityRatio = density / constructedComponent.density()
+            constructedComponent.changeNDensByFactor(densityRatio)
+
+            runLog.important(
+                "A custom material density was specified in the custom isotopics for non-custom "
+                "material {}. The component density has been altered to "
+                "{}.".format(mat, constructedComponent.density()),
+                single=True,
+            )
+
     def _conformKwargs(self, blueprint, matMods):
         """This method gets the relevant kwargs to construct the component."""
         kwargs = {"mergeWith": self.mergeWith or "", "isotopics": self.isotopics or ""}

armi/reactor/blueprints/isotopicOptions.py

@@ -393,15 +393,12 @@ def apply(self, material):
         material.massFrac = dict(self.massFracs)
         if self.density is not None:
             if not isinstance(material, materials.Custom):
-                runLog.warning(
-                    "You either specified a custom mass density or number densities "
-                    "(which implies a mass density) on `{}` with custom isotopics `{}`. "
-                    "This has no effect on this Material class; you can only "
-                    "override mass density on `Custom` "
-                    "materials. Consider switching to number fraction input. "
-                    "Continuing to use {} mass density.".format(
-                        material, self.name, material
-                    )
+                runLog.important(
+                    "A custom density or number densities has been specified for non-custom "
+                    "material {}. The material object's density will not be updated to prevent unintentional "
+                    "density changes across the model. Only custom materials may have a density "
+                    "specified.".format(material),
+                    single=True,
                 )
                 # specifically, non-Custom materials only use refDensity and dLL, mat.customDensity has no effect
                 return