diff --git a/openmc/element.py b/openmc/element.py
index 1416ba1eb6..1f72115cc4 100644
--- a/openmc/element.py
+++ b/openmc/element.py
@@ -193,7 +193,7 @@ class Element(object):
                 # Adjust the abundances for the absent nuclides
                 for nuclide in absent_nuclides:
 
-                    if nuclide == 'O18' and 'O16' in mutual_nuclides:
+                    if nuclide in ['O17', 'O18'] and 'O16' in mutual_nuclides:
                         abundances['O16'] += NATURAL_ABUNDANCE[nuclide]
                     elif nuclide == 'Ta180' and 'Ta181' in mutual_nuclides:
                         abundances['Ta181'] += NATURAL_ABUNDANCE[nuclide]
@@ -253,7 +253,7 @@ class Element(object):
         for nuclide, abundance in abundances.items():
             nuc = openmc.Nuclide(nuclide)
             nuc.scattering = self.scattering
-            pct = float('{:.14}'.format(percent*abundance))
+            pct = round(percent*abundance, 12)
             isotopes.append((nuc, pct, percent_type))
 
         return isotopes
diff --git a/tests/test_triso/inputs_true.dat b/tests/test_triso/inputs_true.dat
index 856581fdef..0ca3943f42 100644
--- a/tests/test_triso/inputs_true.dat
+++ b/tests/test_triso/inputs_true.dat
@@ -1 +1 @@
-5859cd73807c74cce612275817d3e1c6a2b55a347b31925115dbda2d83df60345ea4617cbc3b057a2fcfef4242f0e53d66d569ecffaeed35975ca28307b354c4
\ No newline at end of file
+3a356b5b6d0aaa3db8c601521e1837a6870c5e5f6d1068f4f3e9b896c0107517d99ff9676311221633169b4d79dc1c4076bff84130e6de16df7ace4da5481a60
\ No newline at end of file
diff --git a/tests/test_triso/plots.xml b/tests/test_triso/plots.xml
new file mode 100644
index 0000000000..60ae7d9d8f
--- /dev/null
+++ b/tests/test_triso/plots.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0"?>
+<plots>
+  <plot id="1" type="slice" basis="xy" color="material"
+    origin="0.0 0.0 0.0" width="1.0 1.0" pixels="400 400">
+  </plot>
+</plots>
diff --git a/tests/test_triso/results_true.dat b/tests/test_triso/results_true.dat
index 1716b67f53..15107e8c84 100644
--- a/tests/test_triso/results_true.dat
+++ b/tests/test_triso/results_true.dat
@@ -1,2 +1,2 @@
 k-combined:
-1.643727E+00 5.233644E-02
+1.636336E+00 1.154000E-01
diff --git a/tests/test_triso/test_triso.py b/tests/test_triso/test_triso.py
index e79b9fa8c8..685034491f 100644
--- a/tests/test_triso/test_triso.py
+++ b/tests/test_triso/test_triso.py
@@ -19,33 +19,34 @@ class TRISOTestHarness(PyAPITestHarness):
         # Define TRISO matrials
         fuel = openmc.Material()
         fuel.set_density('g/cm3', 10.5)
-        fuel.add_element('U', 0.14154, 'ao', 14.0)
-        fuel.add_element('C', 0.5)
-        fuel.add_element('O', 1.5)
+        fuel.add_nuclide('U235', 0.14154)
+        fuel.add_nuclide('U238', 0.85846)
+        fuel.add_nuclide('C0', 0.5)
+        fuel.add_nuclide('O16', 1.5)
 
         porous_carbon = openmc.Material()
         porous_carbon.set_density('g/cm3', 1.0)
-        porous_carbon.add_element('C', 1.0)
+        porous_carbon.add_nuclide('C0', 1.0)
         porous_carbon.add_s_alpha_beta('c_Graphite')
 
         ipyc = openmc.Material()
         ipyc.set_density('g/cm3', 1.90)
-        ipyc.add_element('C', 1.0)
+        ipyc.add_nuclide('C0', 1.0)
         ipyc.add_s_alpha_beta('c_Graphite')
 
         sic = openmc.Material()
         sic.set_density('g/cm3', 3.20)
         sic.add_element('Si', 1.0)
-        sic.add_element('C', 1.0)
+        sic.add_nuclide('C0', 1.0)
 
         opyc = openmc.Material()
         opyc.set_density('g/cm3', 1.87)
-        opyc.add_element('C', 1.0)
+        opyc.add_nuclide('C0', 1.0)
         opyc.add_s_alpha_beta('c_Graphite')
 
         graphite = openmc.Material()
         graphite.set_density('g/cm3', 1.1995)
-        graphite.add_element('C', 1.0)
+        graphite.add_nuclide('C0', 1.0)
         graphite.add_s_alpha_beta('c_Graphite')
 
         # Create TRISO particles