Ensuring we only calculate smear density for pinned blocks (#1933)

armi/reactor/blocks.py

@@ -205,9 +205,10 @@ def getSmearDensity(self, cold=True):
         all the area is fuel, it has 100% smear density. Lower smear density allows more room for
         swelling.
 
-        .. warning:: This requires circular fuel and circular cladding. Designs that vary
-            from this will be wrong. It may make sense in the future to put this somewhere a
-            bit more design specific.
+        Warning
+        -------
+        This requires circular fuel and circular cladding. Designs that vary from this will be
+        wrong. It may make sense in the future to put this somewhere a bit more design specific.
 
         Notes
         -----
@@ -225,12 +226,16 @@ def getSmearDensity(self, cold=True):
 
         Returns
         -------
-        smearDensity : float
-            The smear density as a fraction
+        float
+            The smear density as a fraction.
         """
         fuels = self.getComponents(Flags.FUEL)
         if not fuels:
-            return 0.0  # Smear density is not computed for non-fuel blocks
+            # smear density is not computed for non-fuel blocks
+            return 0.0
+        elif not self.getNumPins():
+            # smear density is only defined for pinned blocks
+            return 0.0
 
         circles = self.getComponentsOfShape(components.Circle)
         if not circles:

armi/reactor/tests/test_blocks.py

@@ -395,6 +395,21 @@ def test_getSmearDensityMultipleLiner(self):
         ) / self.block.getDim(Flags.INNER | Flags.LINER, "id") ** 2
         self.assertAlmostEqual(cur, ref, places=10)
 
+    def test_getSmearDensityEdgeCases(self):
+        # show smear density is not computed for non-fuel blocks
+        b0 = blocks.Block("DummyReflectorBlock")
+        self.assertEqual(b0.getSmearDensity(), 0.0)
+
+        # show smear density is only defined for pinned fuel blocks
+        b1 = blocks.HexBlock("TestFuelHexBlock")
+        b1.setType("fuel")
+        b1.p.nPins = 0
+        fuel = components.Circle(
+            "fuel", "UZr", Tinput=25.0, Thot=25.0, od=0.84, id=0.6, mult=0
+        )
+        b1.add(fuel)
+        self.assertEqual(b1.getSmearDensity(), 0.0)
+
     def test_timeNodeParams(self):
         self.block.p["buRate", 3] = 0.1
         self.assertEqual(0.1, self.block.p[("buRate", 3)])