Conserve mass at component level for a.setBlockMesh()

a.setBlockMesh() had an option, `conserveMassFlag="auto"`, which would
try to automatically conserve mass of the fuel while allowing other
components to change mass with changing block heights. This conservation
was based upon getting the nuclides associated with the fuel component,
and then scaling the density of those nuclides based on the change in
block height using b.setNumberDensities().

This method does not work when the fuel has nuclides that are also in
other components of the block, like cladding or structure. In this case,
the mass of those components will also be conserved, which is not the
desired behavior.

Instead, a.setBlockMesh() needs to conserve mass by setting number
densities directly on the components where mass needs to be conserved,
instead of setting the densities on the full block.

armi/reactor/assemblies.py

@@ -673,7 +673,7 @@ def makeAxialSnapList(self, refAssem=None, refMesh=None, force=False):
 
     def _shouldMassBeConserved(self, belowFuelColumn, b):
         """
-        Determine from a rule set if the mass of a block should be conserved during axial expansion.
+        Determine from a rule set if the mass of a block component should be conserved during axial expansion.
 
         Parameters
         ----------
@@ -689,8 +689,8 @@ def _shouldMassBeConserved(self, belowFuelColumn, b):
         conserveMass : boolean
             Should the mass be conserved in this block
 
-        adjustList : list of nuclides
-            What nuclides should have their mass conserved (if any)
+        conserveComponents : list of components
+            What components should have their mass conserved (if any)
 
         belowFuelColumn : boolean
             Update whether the block is above or below a fuel column
@@ -703,30 +703,31 @@ def _shouldMassBeConserved(self, belowFuelColumn, b):
         if b.hasFlags(Flags.FUEL):
             # fuel block
             conserveMass = True
-            adjustList = b.getComponent(Flags.FUEL).getNuclides()
+            conserveComponents = b.getComponents(Flags.FUEL)
         elif self.hasFlags(Flags.FUEL):
             # non-fuel block of a fuel assembly.
             if belowFuelColumn:
                 # conserve mass of everything below the fuel so as to not invalidate
                 # grid-plate dose calcs.
                 conserveMass = True
-                adjustList = b.getNuclides()
                 # conserve mass of everything except coolant.
-                coolant = b.getComponent(Flags.COOLANT)
-                coolantList = coolant.getNuclides() if coolant else []
-                for nuc in coolantList:
-                    if nuc in adjustList:
-                        adjustList.remove(nuc)
+                conserveComponents = [
+                    comp
+                    for comp in b.getComponents()
+                    if not comp.hasFlags(
+                        [Flags.COOLANT, Flags.INTERCOOLANT, Flags.INTERDUCTCOOLANT]
+                    )
+                ]
             else:
                 # plenum or above block in fuel assembly. don't conserve mass.
                 conserveMass = False
-                adjustList = None
+                conserveComponents = []
         else:
             # non fuel block in non-fuel assem. Don't conserve mass.
             conserveMass = False
-            adjustList = None
+            conserveComponents = []
 
-        return conserveMass, adjustList
+        return conserveMass, conserveComponents
 
     def setBlockMesh(self, blockMesh, conserveMassFlag=False, adjustList=None):
         """
@@ -796,15 +797,19 @@ def setBlockMesh(self, blockMesh, conserveMassFlag=False, adjustList=None):
                 return
 
             if conserveMassFlag == "auto":
-                conserveMass, adjustList = self._shouldMassBeConserved(
+                conserveMass, conserveComponents = self._shouldMassBeConserved(
                     belowFuelColumn, b
                 )
             else:
                 conserveMass = conserveMassFlag
-
-            b.setHeight(
-                newTop - zBottom, conserveMass=conserveMass, adjustList=adjustList
-            )
+                conserveComponents = b.getComponents()
+
+            oldBlockHeight = b.getHeight()
+            b.setHeight(newTop - zBottom, conserveMass=False)
+            if conserveMass:
+                heightRatio = oldBlockHeight / b.getHeight()
+                for c in conserveComponents:
+                    c.changeNDensByFactor(heightRatio)
             zBottom = newTop
 
         self.calculateZCoords()