allow nonuniform assemblies

armi/reactor/assemblies.py

@@ -713,8 +713,13 @@ def setBlockMesh(self, blockMesh, conserveMassFlag=False, adjustList=None):
         belowFuelColumn = True
 
         if self[-1].p.topIndex == 0:
-            # this appears to not have been initialized, so initialize it
-            self.makeAxialSnapList(refMesh=blockMesh)
+            runLog.warning(
+                "Reference uniform mesh not being applied to {}. It was likely "
+                "excluded through the setting `nonUniformAssemFlags`.".format(
+                    self.p.type
+                )
+            )
+            return
 
         for b in self:
             if b.isFuel():

armi/reactor/blockParameters.py

@@ -366,7 +366,12 @@ def buGroupNum(self, buGroupNum):  # pylint: disable=method-hidden
         pb.defParam(
             "topIndex",
             units="",
-            description="the axial block index within its parent assembly (0 is bottom block)",
+            description=(
+                "the axial block index within its parent assembly (0 is bottom block). This index with"
+                "regard to the mesh of the reference assembly so it does not increase by 1 for each block."
+                "It is used to keep the mesh of the assemblies uniform with axial expansion."
+                "See setBlockMesh, makeAxialSnapList",
+            ),
             default=0,
             saveToDB=True,
             categories=[parameters.Category.retainOnReplacement],

armi/reactor/reactors.py

@@ -2251,6 +2251,7 @@ def processLoading(self, cs, dbLoad: bool = False):
                 "Please make sure that this is intended and not a input error."
             )
 
+        nonUniformAssems = [Flags.fromString(t) for t in cs["nonUniformAssemFlags"]]
         if dbLoad:
             # reactor.blueprints.assemblies need to be populated
             # this normally happens during armi/reactor/blueprints/__init__.py::constructAssem
@@ -2268,6 +2269,8 @@ def processLoading(self, cs, dbLoad: bool = False):
                     reverse=True,
                 )[0]
                 for a in self.parent.blueprints.assemblies.values():
+                    if a.hasFlags(nonUniformAssems, exact=True):
+                        continue
                     a.makeAxialSnapList(refAssem=finestAssemblyMesh)
 
         else:
@@ -2278,6 +2281,8 @@ def processLoading(self, cs, dbLoad: bool = False):
             if not cs["detailedAxialExpansion"]:
                 # prepare core for mesh snapping during axial expansion
                 for a in self.getAssemblies(includeAll=True):
+                    if a.hasFlags(nonUniformAssems, exact=True):
+                        continue
                     a.makeAxialSnapList(self.refAssem)
 
             if not cs["inputHeightsConsideredHot"]:

armi/settings/fwSettings/globalSettings.py

@@ -106,6 +106,7 @@
 CONF_OUTPUT_CACHE_LOCATION = "outputCacheLocation"
 CONF_MATERIAL_NAMESPACE_ORDER = "materialNamespaceOrder"
 CONF_DETAILED_AXIAL_EXPANSION = "detailedAxialExpansion"
+CONF_NON_UNIFORM_ASSEM_FLAGS = "nonUniformAssemFlags"
 CONF_BLOCK_AUTO_GRID = "autoGenerateBlockGrids"
 CONF_INPUT_HEIGHTS_HOT = "inputHeightsConsideredHot"
 CONF_CYCLES = "cycles"
@@ -164,6 +165,17 @@ def defineSettings() -> List[setting.Setting]:
                 "axial mesh. Neutronics kernel must be able to handle."
             ),
         ),
+        setting.Setting(
+            CONF_NON_UNIFORM_ASSEM_FLAGS,
+            default=[],
+            label="Non Uniform Assem Flags",
+            description=(
+                "Assemblies that match a flag group on this list will not have their "
+                "mesh changed with the reference mesh of the core for uniform mesh cases (non-"
+                "detailed axial expansion). Another plugin may need to make the mesh uniform if "
+                "necessary."
+            ),
+        ),
         setting.Setting(
             CONF_INPUT_HEIGHTS_HOT,
             default=True,