diff --git a/openmc/arithmetic.py b/openmc/arithmetic.py
index c565cda0db..c723fb3e99 100644
--- a/openmc/arithmetic.py
+++ b/openmc/arithmetic.py
@@ -543,8 +543,6 @@ class AggregateFilter:
 
     def __init__(self, aggregate_filter, bins=None, aggregate_op=None):
 
-        self._type = '{}({})'.format(aggregate_op,
-                                     aggregate_filter.short_name.lower())
         self._type = f'{aggregate_op}({aggregate_filter.short_name.lower()})'
         self._bins = None
 
diff --git a/openmc/checkvalue.py b/openmc/checkvalue.py
index 3c76890f75..09ee4e400e 100644
--- a/openmc/checkvalue.py
+++ b/openmc/checkvalue.py
@@ -28,7 +28,7 @@ def check_type(name, value, expected_type, expected_iter_type=None, *, none_ok=F
 
     if not isinstance(value, expected_type):
         if isinstance(expected_type, Iterable):
-            msg = 'Unable to set "{}" to "{}" which is not one of the ' \
+            msg = f'Unable to set "{}" to "{}" which is not one of the ' \
                   'following types: "{}"'.format(name, value, ', '.join(
                       [t.__name__ for t in expected_type]))
         else:
diff --git a/openmc/cmfd.py b/openmc/cmfd.py
index 52665035f3..f9bd83f9bc 100644
--- a/openmc/cmfd.py
+++ b/openmc/cmfd.py
@@ -251,7 +251,7 @@ class CMFDMesh:
 
     def _display_mesh_warning(self, mesh_type, variable_label):
         if self._mesh_type != mesh_type:
-            warn_msg = ('Setting {variable_label} if mesh type is not set to '
+            warn_msg = (f'Setting {variable_label} if mesh type is not set to '
                         '{mesh_type} will have no effect')
             warnings.warn(warn_msg, RuntimeWarning)
 
diff --git a/openmc/filter.py b/openmc/filter.py
index fd1be41e3b..a9e9f2433e 100644
--- a/openmc/filter.py
+++ b/openmc/filter.py
@@ -1111,7 +1111,7 @@ class RealFilter(Filter):
         for pair0, pair1 in zip(bins[:-1], bins[1:]):
             # Successive pairs should be ordered
             if pair1[1] < pair0[1]:
-                raise ValueError('Values {pair1[1]} and {pair0[1]} appear to '
+                raise ValueError(f'Values {pair1[1]} and {pair0[1]} appear to '
                                  'be out of order')
 
     def can_merge(self, other):
@@ -1414,7 +1414,7 @@ class DistribcellFilter(Filter):
 
         # Make sure there is only 1 bin.
         if not len(bins) == 1:
-            msg =(f'Unable to add bins "{bins}" to a DistribcellFilter since '
+            msg = (f'Unable to add bins "{bins}" to a DistribcellFilter since '
                   'only a single distribcell can be used per tally')
             raise ValueError(msg)
 
diff --git a/openmc/statepoint.py b/openmc/statepoint.py
index cd8651ea3b..894730cbe9 100644
--- a/openmc/statepoint.py
+++ b/openmc/statepoint.py
@@ -655,7 +655,7 @@ class StatePoint:
             return
 
         if not isinstance(summary, openmc.Summary):
-            msg = 'Unable to link statepoint with "{summary}" which is not a' \
+            msg = f'Unable to link statepoint with "{summary}" which is not a' \
                   'Summary object'
             raise ValueError(msg)
 
diff --git a/openmc/tallies.py b/openmc/tallies.py
index bdeffa8f55..33d059f17c 100644
--- a/openmc/tallies.py
+++ b/openmc/tallies.py
@@ -352,7 +352,7 @@ class Tally(IDManagerMixin):
         visited_nuclides = set()
         for nuc in nuclides:
             if nuc in visited_nuclides:
-                msg = ('Unable to add a duplicate nuclide "{nuc}" to Tally ID='
+                msg = (f'Unable to add a duplicate nuclide "{nuc}" to Tally ID='
                        '"{self.id}" since duplicate nuclides are not supported '
                        'in the OpenMC Python API')
                 raise ValueError(msg)
@@ -684,7 +684,7 @@ class Tally(IDManagerMixin):
         """
 
         if not self.can_merge(other):
-            msg = 'Unable to merge tally ID="{other.id}" with "{self.id}"'
+            msg = f'Unable to merge tally ID="{other.id}" with "{self.id}"'
             raise ValueError(msg)
 
         # Create deep copy of tally to return as merged tally
@@ -921,7 +921,7 @@ class Tally(IDManagerMixin):
                     return test_filter
 
         # If we did not find the Filter, throw an Exception
-        msg = 'Unable to find filter type "{filter_type}" in Tally ' \
+        msg = f'Unable to find filter type "{filter_type}" in Tally ' \
               'ID="{self.id}"'
         raise ValueError(msg)
 
diff --git a/openmc/universe.py b/openmc/universe.py
index 5cfb985793..a8b6d51e98 100644
--- a/openmc/universe.py
+++ b/openmc/universe.py
@@ -327,8 +327,7 @@ class Universe(UniverseBase):
             for obj, color in colors.items():
                 if isinstance(color, str):
                     if color.lower() not in _SVG_COLORS:
-                        raise ValueError("'{}' is not a valid color."
-                                         .format(color))
+                        raise ValueError(f"'{color}' is not a valid color.")
                     colors[obj] = [x/255 for x in
                                    _SVG_COLORS[color.lower()]] + [1.0]
                 elif len(color) == 3:
@@ -402,8 +401,8 @@ class Universe(UniverseBase):
         """
 
         if not isinstance(cell, openmc.Cell):
-            msg = 'Unable to add a Cell to Universe ID="{0}" since "{1}" is not ' \
-                  'a Cell'.format(self._id, cell)
+            msg = f'Unable to add a Cell to Universe ID="{self._id}" since ' \
+                  '"{cell}" is not a Cell'
             raise TypeError(msg)
 
         cell_id = cell.id
@@ -422,8 +421,8 @@ class Universe(UniverseBase):
         """
 
         if not isinstance(cells, Iterable):
-            msg = 'Unable to add Cells to Universe ID="{0}" since "{1}" is not ' \
-                  'iterable'.format(self._id, cells)
+            msg = f'Unable to add Cells to Universe ID="{self._id}" since ' \
+                  '"{cells}" is not iterable'
             raise TypeError(msg)
 
         for cell in cells:
@@ -440,8 +439,8 @@ class Universe(UniverseBase):
         """
 
         if not isinstance(cell, openmc.Cell):
-            msg = 'Unable to remove a Cell from Universe ID="{0}" since "{1}" is ' \
-                  'not a Cell'.format(self._id, cell)
+            msg = f'Unable to remove a Cell from Universe ID="{self._id}" ' \
+                  'since "{cell}" is not a Cell'
             raise TypeError(msg)
 
         # If the Cell is in the Universe's list of Cells, delete it
@@ -492,10 +491,10 @@ class Universe(UniverseBase):
                 nuclides[name] = (nuclide, density)
         else:
             raise RuntimeError(
-                'Volume information is needed to calculate microscopic cross '
-                'sections for universe {}. This can be done by running a '
-                'stochastic volume calculation via the '
-                'openmc.VolumeCalculation object'.format(self.id))
+                f'Volume information is needed to calculate microscopic cross '
+                'sections for universe {self.id}. This can be done by running '
+                'a stochastic volume calculation via the '
+                'openmc.VolumeCalculation object')
 
         return nuclides
 
@@ -586,10 +585,10 @@ class Universe(UniverseBase):
         """Count the number of instances for each cell in the universe, and
         record the count in the :attr:`Cell.num_instances` properties."""
 
-        univ_path = path + 'u{}'.format(self.id)
+        univ_path = path + f'u{self.id}'
 
         for cell in self.cells.values():
-            cell_path = '{}->c{}'.format(univ_path, cell.id)
+            cell_path = f'{univ_path}->c{cell.id}'
             fill = cell._fill
             fill_type = cell.fill_type
 
@@ -619,7 +618,7 @@ class Universe(UniverseBase):
                 if mat is not None:
                     mat._num_instances += 1
                     if not instances_only:
-                        mat._paths.append('{}->m{}'.format(cell_path, mat.id))
+                        mat._paths.append(f'{cell_path}->m{mat.id}')
 
             # Append current path
             cell._num_instances += 1
diff --git a/openmc/volume.py b/openmc/volume.py
index 7a9ef17371..7c86f1fe9e 100644
--- a/openmc/volume.py
+++ b/openmc/volume.py
@@ -102,9 +102,9 @@ class VolumeCalculation:
                     if (np.any(np.asarray(lower_left) > ll) or
                         np.any(np.asarray(upper_right) < ur)):
                         warnings.warn(
-                            "Specified bounding box is smaller than computed "
-                            "bounding box for cell {}. Volume calculation may "
-                            "be incorrect!".format(c.id))
+                            f"Specified bounding box is smaller than computed "
+                            "bounding box for cell {c.id}. Volume calculation "
+                            "may be incorrect!")
 
             self.lower_left = lower_left
             self.upper_right = upper_right