Clean up a minor bug in #1653

armi/physics/neutronics/crossSectionGroupManager.py

@@ -1235,12 +1235,12 @@ def createRepresentativeBlocksUsingExistingBlocks(
 
             # create a new block collection that inherits all of the properties
             # and settings from oldBlockCollection.
-            if len(oldBlockCollection._validRepresentativeBlockTypes) > 0:
-                validBlockTypes = []
-                for flag in oldBlockCollection._validRepresentativeBlockTypes:
-                    validBlockTypes.append(flags._toString(Flags, flag))
-            else:
-                validBlockTypes = None
+            validBlockTypes = oldBlockCollection._validRepresentativeBlockTypes
+            if validBlockTypes is not None and len(validBlockTypes) > 0:
+                validBlockTypes = [
+                    flags._toString(Flags, flag)
+                    for flag in oldBlockCollection._validRepresentativeBlockTypes
+                ]
             newBlockCollection = oldBlockCollection.__class__(
                 oldBlockCollection.allNuclidesInProblem,
                 validBlockTypes=validBlockTypes,

armi/physics/neutronics/tests/test_crossSectionManager.py

@@ -816,16 +816,8 @@ def test_getRepresentativeBlocks(self):
         self.assertIsNone(blocks[0].p.detailedNDens)
         self.assertIsNone(blocks[1].p.detailedNDens)
 
-    def test_createRepresentativeBlocksUsingExistingBlocks(self):
-        """
-        Demonstrates that a new representative block can be generated from an existing
-        representative block.
-
-        Notes
-        -----
-        This tests that the XS ID of the new representative block is correct and that the
-        compositions are identical between the original and the new representative blocks.
-        """
+    def _createRepresentativeBlocksUsingExistingBlocks(self, validBlockTypes):
+        """Reusable code used in multiple unit tests."""
         o, r = test_reactors.loadTestReactor(
             TEST_ROOT, inputFileName="smallestTestReactor/armiRunSmallest.yaml"
         )
@@ -843,7 +835,7 @@ def test_createRepresentativeBlocksUsingExistingBlocks(self):
             }
         )
         o.cs[CONF_CROSS_SECTION].setDefaults(
-            crossSectionGroupManager.AVERAGE_BLOCK_COLLECTION, ["fuel"]
+            crossSectionGroupManager.AVERAGE_BLOCK_COLLECTION, validBlockTypes
         )
         aaSettings = o.cs[CONF_CROSS_SECTION]["AA"]
         self.csm.cs = copy.deepcopy(o.cs)
@@ -877,6 +869,30 @@ def test_createRepresentativeBlocksUsingExistingBlocks(self):
                 continue
             self.assertEqual(baSettingValue, aaSettings.__dict__[setting])
 
+    def test_createRepresentativeBlocksUsingExistingBlocks(self):
+        """
+        Demonstrates that a new representative block can be generated from an existing
+        representative block.
+
+        Notes
+        -----
+        This tests that the XS ID of the new representative block is correct and that the
+        compositions are identical between the original and the new representative blocks.
+        """
+        self._createRepresentativeBlocksUsingExistingBlocks(["fuel"])
+
+    def test_createRepresentativeBlocksUsingExistingBlocksDisableValidBlockTypes(self):
+        """
+        Demonstrates that a new representative block can be generated from an existing
+        representative block with the setting `disableBlockTypeExclusionInXsGeneration: true`.
+
+        Notes
+        -----
+        This tests that the XS ID of the new representative block is correct and that the
+        compositions are identical between the original and the new representative blocks.
+        """
+        self._createRepresentativeBlocksUsingExistingBlocks(True)
+
     def test_interactBOL(self):
         """Test `BOL` lattice physics update frequency.
 

doc/release/0.3.rst

@@ -53,7 +53,7 @@ Bug Fixes
 ---------
 #. Fixed four bugs with "corners up" hex grids. (`PR#1649 <https://github.com/terrapower/armi/pull/1649>`_)
 #. Fixed ``safeCopy`` to work on both Windows and Linux with strict permissions (`PR#1691 <https://github.com/terrapower/armi/pull/1691>`_)
-#. When creating a new XS group, inherit settings from initial group. (`PR#1653 <https://github.com/terrapower/armi/pull/1653>`_)
+#. When creating a new XS group, inherit settings from initial group. (`PR#1653 <https://github.com/terrapower/armi/pull/1653>`_, `PR#1751 <https://github.com/terrapower/armi/pull/1751>`_)
 
 #. TBD