diff --git a/examples/jupyter/mgxs-part-ii.ipynb b/examples/jupyter/mgxs-part-ii.ipynb
index c10f55956..1058b7134 100644
--- a/examples/jupyter/mgxs-part-ii.ipynb
+++ b/examples/jupyter/mgxs-part-ii.ipynb
@@ -2048,8 +2048,8 @@
     "o16 = df[df['nuclide'] == 'O16']['mean']\n",
     "\n",
     "# Cast DataFrames as NumPy arrays\n",
-    "h1 = h1.as_matrix()\n",
-    "o16 = o16.as_matrix()\n",
+    "h1 = h1.values\n",
+    "o16 = o16.values\n",
     "\n",
     "# Reshape arrays to 2D matrix for plotting\n",
     "h1.shape = (fine_groups.num_groups, fine_groups.num_groups)\n",
diff --git a/openmc/arithmetic.py b/openmc/arithmetic.py
index 4a5e7486a..91e2f1ed4 100644
--- a/openmc/arithmetic.py
+++ b/openmc/arithmetic.py
@@ -1,6 +1,6 @@
 import sys
 import copy
-from collections import Iterable
+from collections.abc import Iterable
 
 import numpy as np
 import pandas as pd
diff --git a/openmc/data/photon.py b/openmc/data/photon.py
index 61c903158..e0f71d5ce 100644
--- a/openmc/data/photon.py
+++ b/openmc/data/photon.py
@@ -1,4 +1,5 @@
-from collections import OrderedDict, Mapping, Callable
+from collections import OrderedDict
+from collections.abc import Mapping, Callable
 from copy import deepcopy
 from io import StringIO
 from numbers import Integral, Real
@@ -740,7 +741,7 @@ class IncidentPhoton(EqualityMixin):
                         shell_values.insert(0, None)
                         df = relax.transitions[shell].replace(
                             shell_values, range(len(shell_values)))
-                        sub_group.create_dataset('transitions', data=df.as_matrix())
+                        sub_group.create_dataset('transitions', data=df.values)
 
                 # Determine threshold
                 threshold = rx.xs.x[0]
diff --git a/openmc/data/reaction.py b/openmc/data/reaction.py
index 547208dae..11807cadc 100644
--- a/openmc/data/reaction.py
+++ b/openmc/data/reaction.py
@@ -924,7 +924,7 @@ class Reaction(EqualityMixin):
         rx = cls(mt)
         rx.q_value = group.attrs['Q_value']
         rx.center_of_mass = bool(group.attrs['center_of_mass'])
-        rx.redundant = bool(group.attrs['redundant'])
+        rx.redundant = bool(group.attrs.get('redundant', False))
 
         # Read cross section at each temperature
         for T, Tgroup in group.items():
diff --git a/openmc/data/resonance_covariance.py b/openmc/data/resonance_covariance.py
index 300e6dbf6..9e80e52f2 100644
--- a/openmc/data/resonance_covariance.py
+++ b/openmc/data/resonance_covariance.py
@@ -1,4 +1,4 @@
-from collections import MutableSequence
+from collections.abc import MutableSequence
 import warnings
 import io
 import copy
diff --git a/openmc/filter.py b/openmc/filter.py
index 6c904e61d..ef68a4961 100644
--- a/openmc/filter.py
+++ b/openmc/filter.py
@@ -1,5 +1,6 @@
 from abc import ABCMeta
-from collections import Iterable, OrderedDict
+from collections import OrderedDict
+from collections.abc import Iterable
 import copy
 import hashlib
 from itertools import product
diff --git a/openmc/mesh.py b/openmc/mesh.py
index f7cba22f8..f454a6f88 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -1,4 +1,4 @@
-from collections import Iterable
+from collections.abc import Iterable
 from numbers import Real, Integral
 from xml.etree import ElementTree as ET
 import sys
diff --git a/openmc/mgxs/groups.py b/openmc/mgxs/groups.py
index 6dd56e8e7..338bc4b00 100644
--- a/openmc/mgxs/groups.py
+++ b/openmc/mgxs/groups.py
@@ -1,4 +1,4 @@
-from collections import Iterable
+from collections.abc import Iterable
 from numbers import Real
 import copy
 import sys
diff --git a/openmc/universe.py b/openmc/universe.py
index 294b114dd..044da12e3 100644
--- a/openmc/universe.py
+++ b/openmc/universe.py
@@ -1,4 +1,5 @@
-from collections import OrderedDict, Iterable
+from collections import OrderedDict
+from collections.abc import Iterable
 from copy import copy, deepcopy
 from numbers import Integral, Real
 import random
diff --git a/tests/unit_tests/test_data_decay.py b/tests/unit_tests/test_data_decay.py
index be8ad7d64..b925506df 100644
--- a/tests/unit_tests/test_data_decay.py
+++ b/tests/unit_tests/test_data_decay.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-from collections import Mapping
+from collections.abc import Mapping
 import os
 from math import log
 
diff --git a/tests/unit_tests/test_data_misc.py b/tests/unit_tests/test_data_misc.py
index 34686b567..46a9dbd02 100644
--- a/tests/unit_tests/test_data_misc.py
+++ b/tests/unit_tests/test_data_misc.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-from collections import Mapping
+from collections.abc import Mapping
 import os
 
 import numpy as np
diff --git a/tests/unit_tests/test_data_neutron.py b/tests/unit_tests/test_data_neutron.py
index bbebcb34a..3cf036aa2 100644
--- a/tests/unit_tests/test_data_neutron.py
+++ b/tests/unit_tests/test_data_neutron.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-from collections import Mapping, Callable
+from collections.abc import Mapping, Callable
 import os
 
 import numpy as np
diff --git a/tests/unit_tests/test_data_photon.py b/tests/unit_tests/test_data_photon.py
index eecef73c4..5036d08fd 100644
--- a/tests/unit_tests/test_data_photon.py
+++ b/tests/unit_tests/test_data_photon.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-from collections import Mapping, Callable
+from collections.abc import Mapping, Callable
 import os
 
 import numpy as np
diff --git a/tests/unit_tests/test_data_thermal.py b/tests/unit_tests/test_data_thermal.py
index 9def78b38..7d7d4e964 100644
--- a/tests/unit_tests/test_data_thermal.py
+++ b/tests/unit_tests/test_data_thermal.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-from collections import Callable
+from collections.abc import Callable
 import os
 
 import numpy as np