From 2c2469843768233b5715f28148c7ab73b0d76041 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Wed, 11 Mar 2026 17:46:20 -0500
Subject: [PATCH 01/11] Fix MPI behavior in _KeffSearchControl._update_vec

---
 openmc/deplete/keff_search_control.py | 115 ++++++++++++--------------
 1 file changed, 55 insertions(+), 60 deletions(-)

diff --git a/openmc/deplete/keff_search_control.py b/openmc/deplete/keff_search_control.py
index fc8652154..b39d667b5 100644
--- a/openmc/deplete/keff_search_control.py
+++ b/openmc/deplete/keff_search_control.py
@@ -1,14 +1,15 @@
-import openmc.lib
-from openmc.mpi import comm
 from typing import Callable
 from warnings import warn
 
+import openmc.lib
+
+
 class _KeffSearchControl:
     """Controller for keff search during depletion calculations.
-    
-    This class performs keff searches to maintain a target keff by adjusting
-    a model parameter through a provided function.
-    
+
+    This class performs keff searches to maintain a target keff by adjusting a
+    model parameter through a provided function.
+
     Parameters
     ----------
     operator : openmc.deplete.Operator
@@ -20,11 +21,12 @@ class _KeffSearchControl:
     x1 : float
         Initial upper bound for the keff search
     bracket : list[float]
-        Absolute bracketing interval lower and upper
-        if keff search solution lies off these limits the closest
-        limit will be set as new result.
-    search_kwargs : dict, optional
-        Additional keyword arguments to pass to `model.keff_search`
+        Absolute bracketing interval lower and upper. If the keff search
+        solution lies off these limits the closest limit will be set as new
+        result.
+    **search_kwargs : dict, optional
+        Additional keyword arguments to pass to :meth:`openmc.Model.keff_search`
+
     """
     def __init__(self, operator, function: Callable, x0: float, x1: float, bracket: list[float], **search_kwargs):
         if len(bracket) != 2:
@@ -41,14 +43,14 @@ class _KeffSearchControl:
 
     def search_for_keff(self, x, step_index):
         """Perform keff search and update the atom density vector.
-        
+
         Parameters
         ----------
         x : list of numpy.ndarray
             Current atom density vector (atoms per material)
         step_index : int
             Current depletion step index
-            
+
         Returns
         -------
         x : list of numpy.ndarray
@@ -59,26 +61,26 @@ class _KeffSearchControl:
         root = self._search_for_keff()
         x = self._update_vec(x)
         return x, root
-        
+
     def _search_for_keff(self) -> float:
         """Perform the keff search using the model's keff_search method.
-        
+
         Returns
         -------
         float
             Parameter value that achieves target keff
-            
+
         Raises
         ------
         ValueError
             If the keff search fails to converge
         """
-        with openmc.lib.TemporarySession(model=self.operator.model) as session:
+        with openmc.lib.TemporarySession(self.operator.model):
             # Only pass the first 3 required args plus explicitly provided kwargs
             result = self.operator.model.keff_search(
-                self.function, 
-                self.x0, 
-                self.x1, 
+                self.function,
+                self.x0,
+                self.x1,
                 **self.search_kwargs
             )
         if not result.converged:
@@ -86,61 +88,54 @@ class _KeffSearchControl:
                 f"Search for keff failed to converge. "
                 f"Termination reason: {result.flag}"
             )
-        
+
         root = result.root
-        
+
         # Check if root is outside the bracket bounds and give a warning
         if root < self.search_kwargs['x_min']:
-            warn(
-                f"keff search result ({root:.6f}) is below the lower bracket bound "
-                f"({self.search_kwargs['x_min']:.6f}). Clamping to bracket lower bound.",
-                UserWarning
-            )
-
+            warn(f"keff search result ({root:.6f}) is below the lower bracket "
+                 f"bound ({self.search_kwargs['x_min']:.6f}).", UserWarning)
         elif root > self.search_kwargs['x_max']:
-            warn(
-                f"keff search result ({root:.6f}) is above the upper bracket bound "
-                f"({self.search_kwargs['x_max']:.6f}). Clamping to bracket upper bound.",
-                UserWarning
-            )
-        
-        #restore the number of initial batches
+            warn(f"keff search result ({root:.6f}) is above the upper bracket "
+                 f"bound ({self.search_kwargs['x_max']:.6f}).", UserWarning)
+
+        # Restore the number of initial batches
         openmc.lib.settings.set_batches(self.operator.model.settings.batches)
 
         return root
 
     def _update_vec(self, x):
         """Update the atom density vector from openmc.lib.materials and AtomNumber object.
-        
-        This method synchronizes the atom densities across all MPI ranks by
-        broadcasting the number object from each rank and updating the x vector
-        with the current atom densities from openmc.lib.materials or AtomNumber object 
-        if the nuclide is not in openmc.lib.materials.
-        
+
+        The depletion vector ``x`` is rank-local, matching the materials owned
+        by ``self.operator.number`` on the current MPI rank. We therefore only
+        update entries for locally owned materials using the compositions
+        currently stored in ``openmc.lib.materials``.
+
         Parameters
         ----------
         x : list of numpy.ndarray
             Atom density vector to update (atoms per material)
-            
+
         Returns
         -------
         list of numpy.ndarray
-            Updated atom density vector synchronized across all ranks
+            Updated rank-local atom density vector
         """
-        for rank in range(comm.size):
-            number_i = comm.bcast(self.operator.number, root=rank)
-            
-            for mat_idx, mat in enumerate(number_i.materials):
-                for nuc in number_i.nuclides:
-                    if nuc in number_i.burnable_nuclides:
-                        nuc_idx = number_i.burnable_nuclides.index(nuc)
-                        volume = number_i.get_mat_volume(mat) # cm^3
-                        if nuc in openmc.lib.materials[int(mat)].nuclides:
-                            _nuc_idx = openmc.lib.materials[int(mat)].nuclides.index(nuc)
-                            val = 1.0e24 * openmc.lib.materials[int(mat)].densities[_nuc_idx] # atom/cm^3
-                        else:
-                            val = number_i.get_atom_density(mat, nuc) # atom/cm^3
-                        x[mat_idx][nuc_idx] = val * volume
-        
-            x = comm.bcast(x, root=rank)
-        return x
\ No newline at end of file
+        number = self.operator.number
+
+        for mat_idx, mat in enumerate(number.materials):
+            lib_material = openmc.lib.materials[int(mat)]
+            nuclides = lib_material.nuclides
+            densities = 1e24 * lib_material.densities
+            volume = number.get_mat_volume(mat)
+
+            for nuc_idx, nuc in enumerate(number.burnable_nuclides):
+                if nuc in nuclides:
+                    lib_nuc_idx = nuclides.index(nuc)
+                    atom_density = densities[lib_nuc_idx]
+                else:
+                    atom_density = number.get_atom_density(mat, nuc)
+                x[mat_idx][nuc_idx] = atom_density * volume
+
+        return x

From 5af848f6fd91ed02f44753176cf0f84dac7efde6 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Wed, 11 Mar 2026 17:46:39 -0500
Subject: [PATCH 02/11] Style fixes

---
 openmc/deplete/abc.py                         | 13 ++++---------
 .../deplete_with_keff_search_control/test.py  | 19 +++++++++++--------
 .../test_deplete_keff_search_control.py       | 10 +++++++---
 3 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index 2c6d177c4..3d0bc57ea 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -618,11 +618,6 @@ class Integrator(ABC):
         External source rates for the depletion system.
 
         .. versionadded:: 0.15.3
-    keff_search_control : openmc.deplete._KeffSearchControl
-        Instance of _KeffSearchControl class to perform keff search during
-        transport-depletion simulation.
-
-        .. versionadded:: 0.15.4
 
     """)
 
@@ -1115,7 +1110,7 @@ class Integrator(ABC):
             and modify ``openmc.lib`` objects accordingly (e.g., adjust control
             rod position via ``openmc.lib.cells[...].translation``, material
             density via ``openmc.lib.materials[...].set_densities(...)``, etc.).
-            
+
             **Important**: The function must modify ``openmc.lib`` objects, not
             ``openmc.model`` objects.
         x0: float
@@ -1124,7 +1119,7 @@ class Integrator(ABC):
             Initial upper bound for the keff search.
         bracket : list[float]
             Bracket interval [x_min, x_max] that constrains the allowed parameter
-            values during the keff search. This is a required parameter 
+            values during the keff search. This is a required parameter
             that defines the absolute bounds for the search. The bracket must contain
             exactly 2 elements with bracket[0] < bracket[1]. These values are passed
             directly to the ``x_min`` and ``x_max`` optional arguments in
@@ -1186,8 +1181,8 @@ class Integrator(ABC):
 
         """
         self._keff_search_control = _KeffSearchControl(
-            self.operator, 
-            function, 
+            self.operator,
+            function,
             x0,
             x1,
             bracket,
diff --git a/tests/regression_tests/deplete_with_keff_search_control/test.py b/tests/regression_tests/deplete_with_keff_search_control/test.py
index 0af6acd53..c78f21c70 100644
--- a/tests/regression_tests/deplete_with_keff_search_control/test.py
+++ b/tests/regression_tests/deplete_with_keff_search_control/test.py
@@ -79,14 +79,17 @@ def model():
 
     return openmc.Model(geometry, materials, settings)
 
+
 def translate_cell(position):
     cell_trans = [cell for cell in openmc.lib.cells.values() if cell.name == 'trans_cell'][0]
     openmc.lib.cells[cell_trans.id].translation = [0, 0, position]
 
+
 def rotate_cell(angle):
     cell_rot = [cell for cell in openmc.lib.cells.values() if cell.name == 'rot_cell'][0]
     openmc.lib.cells[cell_rot.id].rotation = [0, 0, angle]
 
+
 def adjust_material_density(density_factor):
     f = [material for material in openmc.lib.materials.values() if material.name == 'f'][0]
     nuclides = openmc.lib.materials[f.id].nuclides
@@ -96,12 +99,12 @@ def adjust_material_density(density_factor):
     densities[nuc_idx] = new_density
     openmc.lib.materials[f.id].set_densities(nuclides, densities)
 
-@pytest.mark.parametrize("function, x0, x1, bracket, ref_result", [
-    (translate_cell, -11, -5, [-15,0], 'depletion_with_translation'),
-    (rotate_cell, -80, -50, [-90,0], 'depletion_with_rotation'),
-    (adjust_material_density, 0.5, 2, [0.3, 3.0], 'depletion_with_refuel')
-    ])
 
+@pytest.mark.parametrize("function, x0, x1, bracket, ref_result", [
+    (translate_cell, -11, -5, (-15, 0), 'depletion_with_translation'),
+    (rotate_cell, -80, -50, (-90, 0), 'depletion_with_rotation'),
+    (adjust_material_density, 0.5, 2, (0.3, 3.0), 'depletion_with_refuel')
+])
 def test_keff_search_control(run_in_tmpdir, model, function, x0, x1, bracket, ref_result):
 
     chain_file = Path(__file__).parents[2] / 'chain_simple.xml'
@@ -114,10 +117,10 @@ def test_keff_search_control(run_in_tmpdir, model, function, x0, x1, bracket, re
         x0=x0,
         x1=x1,
         bracket=bracket,
-        output=True, 
-        k_tol=1e-1, 
+        output=True,
+        k_tol=1e-1,
         sigma_final=5e-2)
-    
+
     integrator.integrate()
 
     # Get path to test and reference results
diff --git a/tests/unit_tests/test_deplete_keff_search_control.py b/tests/unit_tests/test_deplete_keff_search_control.py
index 12b4020f0..57e50f0d9 100644
--- a/tests/unit_tests/test_deplete_keff_search_control.py
+++ b/tests/unit_tests/test_deplete_keff_search_control.py
@@ -69,18 +69,21 @@ def integrator(operator):
     return openmc.deplete.PredictorIntegrator(
             operator, [1,1], 0.0, timestep_units = 'd')
 
+
 def translate_cell(position):
     """Helper function to translate a cell"""
     cell = [c for c in openmc.lib.cells.values() if c.name == 'universe_cell'][0]
     openmc.lib.cells[cell.id].translation = [0, 0, position]
     return position
 
+
 def rotate_cell(angle):
     """Helper function to rotate a cell"""
     cell = [c for c in openmc.lib.cells.values() if c.name == 'universe_cell'][0]
     openmc.lib.cells[cell.id].rotation = [0, 0, angle]
     return angle
 
+
 def adjust_fuel_density(density_factor):
     """Helper function to adjust fuel density"""
     fuel = [m for m in openmc.lib.materials.values() if m.name == 'fuel'][0]
@@ -90,6 +93,7 @@ def adjust_fuel_density(density_factor):
     openmc.lib.materials[fuel.id].set_densities(nuclides, new_densities)
     return density_factor
 
+
 @pytest.mark.parametrize("function, x0, x1, bracket, test_value", [
     (translate_cell, -1.0, 1.0, [-5.0, 5.0], 0.5),
     (rotate_cell, -45.0, 45.0, [-90.0, 90.0], 10.0),
@@ -110,12 +114,12 @@ def test_integrator_add_keff_search_control(run_in_tmpdir, model, operator, inte
         k_tol=0.1,
         output=False,
     )
-    
+
     assert integrator.keff_search_control.x0 == x0
     assert integrator.keff_search_control.x1 == x1
     assert integrator.keff_search_control.function == test_function
     assert integrator.keff_search_control.search_kwargs['x_min'] == bracket[0]
-    assert integrator.keff_search_control.search_kwargs['x_max'] == bracket[1]  
+    assert integrator.keff_search_control.search_kwargs['x_max'] == bracket[1]
     assert integrator.keff_search_control.search_kwargs['k_tol'] == 0.1
-    assert integrator.keff_search_control.search_kwargs['output'] == False
+    assert not integrator.keff_search_control.search_kwargs['output']
     openmc.lib.finalize()

From 821bb5ab65f5fdb3f61587b28beb71285a575187 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Wed, 11 Mar 2026 23:52:52 -0500
Subject: [PATCH 03/11] Fix restart with saved keff search

---
 openmc/deplete/abc.py                         | 42 ++++++++++++-------
 openmc/deplete/keff_search_control.py         | 10 +++++
 openmc/model/model.py                         |  6 +--
 .../deplete_with_keff_search_control/test.py  | 20 ++++-----
 .../test_deplete_keff_search_control.py       | 32 +++++++-------
 5 files changed, 63 insertions(+), 47 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index 3d0bc57ea..ed0cd695e 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -903,9 +903,16 @@ class Integrator(ABC):
                     n, res = self._get_bos_data_from_operator(i, source_rate, n)
                 else:
                     n, res = self._get_bos_data_from_restart(source_rate, n)
-                    # Get keff search root from keff search control
-                    if self._keff_search_control:
-                        n, keff_search_root = self._get_bos_from_keff_search_control(i, n)
+                    if self._keff_search_control is not None and source_rate != 0.0:
+                        keff_search_root = res.keff_search_root
+                        if keff_search_root is None:
+                            raise ValueError(
+                                "Cannot restore keff search control from restart "
+                                "results because no stored keff_search_root is "
+                                "available."
+                            )
+                        self._keff_search_control.apply_stored_root(
+                            keff_search_root)
                     else:
                         keff_search_root = None
                 # Solve Bateman equations over time interval
@@ -1100,7 +1107,9 @@ class Integrator(ABC):
             ``openmc.lib.cells``, ``openmc.lib.materials``) and **NOT** through
             ``openmc.model``. The function is called within a
             :class:`openmc.lib.TemporarySession` context where only the C API
-            (``openmc.lib``) is available for modifications.
+            (``openmc.lib``) is available for modifications. The function
+            should behave like a setter for the controlled parameter so that a
+            stored keff-search root can be safely reapplied during restart.
 
         Parameters
         ----------
@@ -1112,7 +1121,9 @@ class Integrator(ABC):
             density via ``openmc.lib.materials[...].set_densities(...)``, etc.).
 
             **Important**: The function must modify ``openmc.lib`` objects, not
-            ``openmc.model`` objects.
+            ``openmc.model`` objects, and should set the controlled parameter
+            directly rather than modifying the current state relative to its
+            existing value.
         x0: float
             Initial lower bound for the keff search.
         x1: float
@@ -1157,23 +1168,22 @@ class Integrator(ABC):
         ...     k_tol=1e-4
         ... )
 
-        Add keff search that adjusts material density:
+        Add keff search that sets the U235 density directly:
 
-        >>> def adjust_material_density(density_factor):
+        >>> def set_u235_density(u235_density):
         ...     # Get the material from openmc.lib
         ...     lib_mat = openmc.lib.materials[material_id]
         ...     # Get current nuclides and densities
         ...     nuclides = lib_mat.nuclides
-        ...     current_densities = lib_mat.densities
-        ...     # Scale all densities by the factor
-        ...     new_densities = densities * density_factor
-        ...     # Update the material densities
-        ...     lib_mat.set_densities(nuclides, new_densities)
+        ...     densities = lib_mat.densities
+        ...     u235_idx = nuclides.index('U235')
+        ...     densities[u235_idx] = u235_density
+        ...     lib_mat.set_densities(nuclides, densities)
         >>> integrator.add_keff_search_control(
-        ...     adjust_material_density,
-        ...     x0=0.8,
-        ...     x1=1.2,
-        ...     bracket=[0.2, 1.5],
+        ...     set_u235_density,
+        ...     x0=5.0e-4,
+        ...     x1=1.0e-3,
+        ...     bracket=[1.0e-4, 2.0e-3],
         ...     target=1.0
         ... )
 
diff --git a/openmc/deplete/keff_search_control.py b/openmc/deplete/keff_search_control.py
index b39d667b5..08263f348 100644
--- a/openmc/deplete/keff_search_control.py
+++ b/openmc/deplete/keff_search_control.py
@@ -62,6 +62,16 @@ class _KeffSearchControl:
         x = self._update_vec(x)
         return x, root
 
+    def apply_stored_root(self, root: float):
+        """Reapply a previously stored control parameter value.
+
+        Parameters
+        ----------
+        root : float
+            Parameter value from a prior keff search result.
+        """
+        self.function(root)
+
     def _search_for_keff(self) -> float:
         """Perform the keff search using the model's keff_search method.
 
diff --git a/openmc/model/model.py b/openmc/model/model.py
index 6e4c1c585..c2d4d6915 100644
--- a/openmc/model/model.py
+++ b/openmc/model/model.py
@@ -1179,8 +1179,8 @@ class Model:
 
         # Convert ID map to RGB image
         img = id_map_to_rgb(
-            id_map=id_map, 
-            color_by=color_by, 
+            id_map=id_map,
+            color_by=color_by,
             colors=colors,
             overlap_color=overlap_color
         )
@@ -1217,7 +1217,7 @@ class Model:
                 extent=(x_min, x_max, y_min, y_max),
                 **contour_kwargs
             )
-            
+
             # If only showing outline, set the axis limits and aspect explicitly
             if outline == 'only':
                 axes.set_xlim(x_min, x_max)
diff --git a/tests/regression_tests/deplete_with_keff_search_control/test.py b/tests/regression_tests/deplete_with_keff_search_control/test.py
index c78f21c70..82e601280 100644
--- a/tests/regression_tests/deplete_with_keff_search_control/test.py
+++ b/tests/regression_tests/deplete_with_keff_search_control/test.py
@@ -90,24 +90,24 @@ def rotate_cell(angle):
     openmc.lib.cells[cell_rot.id].rotation = [0, 0, angle]
 
 
-def adjust_material_density(density_factor):
-    f = [material for material in openmc.lib.materials.values() if material.name == 'f'][0]
-    nuclides = openmc.lib.materials[f.id].nuclides
-    densities = openmc.lib.materials[f.id].densities
+def set_u235_density(u235_density):
+    fuel = [material for material in openmc.lib.materials.values()
+            if material.name == 'f'][0]
+    nuclides = openmc.lib.materials[fuel.id].nuclides
+    densities = openmc.lib.materials[fuel.id].densities
     nuc_idx = nuclides.index('U235')
-    new_density = densities[nuc_idx] * density_factor
-    densities[nuc_idx] = new_density
-    openmc.lib.materials[f.id].set_densities(nuclides, densities)
+    densities[nuc_idx] = u235_density
+    openmc.lib.materials[fuel.id].set_densities(nuclides, densities)
 
 
 @pytest.mark.parametrize("function, x0, x1, bracket, ref_result", [
     (translate_cell, -11, -5, (-15, 0), 'depletion_with_translation'),
     (rotate_cell, -80, -50, (-90, 0), 'depletion_with_rotation'),
-    (adjust_material_density, 0.5, 2, (0.3, 3.0), 'depletion_with_refuel')
+    (set_u235_density, 2e-4, 1e-3, (1e-4, 2e-3), 'depletion_with_refuel')
 ])
 def test_keff_search_control(run_in_tmpdir, model, function, x0, x1, bracket, ref_result):
-
     chain_file = Path(__file__).parents[2] / 'chain_simple.xml'
+    model.settings.verbosity = 1
     op = CoupledOperator(model, chain_file)
 
     integrator = openmc.deplete.PredictorIntegrator(
@@ -118,7 +118,7 @@ def test_keff_search_control(run_in_tmpdir, model, function, x0, x1, bracket, re
         x1=x1,
         bracket=bracket,
         output=True,
-        k_tol=1e-1,
+        k_tol=0.1,
         sigma_final=5e-2)
 
     integrator.integrate()
diff --git a/tests/unit_tests/test_deplete_keff_search_control.py b/tests/unit_tests/test_deplete_keff_search_control.py
index 57e50f0d9..8de4d542c 100644
--- a/tests/unit_tests/test_deplete_keff_search_control.py
+++ b/tests/unit_tests/test_deplete_keff_search_control.py
@@ -84,30 +84,27 @@ def rotate_cell(angle):
     return angle
 
 
-def adjust_fuel_density(density_factor):
-    """Helper function to adjust fuel density"""
+def set_u235_density(u235_density):
+    """Helper function to set the U235 density directly"""
     fuel = [m for m in openmc.lib.materials.values() if m.name == 'fuel'][0]
     nuclides = openmc.lib.materials[fuel.id].nuclides
-    current_densities = openmc.lib.materials[fuel.id].densities
-    new_densities = [d * density_factor for d in current_densities]
-    openmc.lib.materials[fuel.id].set_densities(nuclides, new_densities)
-    return density_factor
+    densities = openmc.lib.materials[fuel.id].densities
+    u235_idx = nuclides.index('U235')
+    densities[u235_idx] = u235_density
+    openmc.lib.materials[fuel.id].set_densities(nuclides, densities)
+    return u235_density
 
 
-@pytest.mark.parametrize("function, x0, x1, bracket, test_value", [
-    (translate_cell, -1.0, 1.0, [-5.0, 5.0], 0.5),
-    (rotate_cell, -45.0, 45.0, [-90.0, 90.0], 10.0),
-    (adjust_fuel_density, 0.8, 1.2, [0.5, 1.5], 1.0)
+@pytest.mark.parametrize("function, x0, x1, bracket", [
+    (translate_cell, -1.0, 1.0, [-5.0, 5.0]),
+    (rotate_cell, -45.0, 45.0, [-90.0, 90.0]),
+    (set_u235_density, 0.8, 1.2, [0.5, 1.5])
 ])
 def test_integrator_add_keff_search_control(run_in_tmpdir, model, operator, integrator,
-    function, x0, x1, bracket, test_value):
+    function, x0, x1, bracket):
     """Test adding add_keff_search_control to integrator"""
-    model.export_to_xml()
-    openmc.lib.init()
-    test_function = function(test_value)
-    # Test that add_reactivity_control method exists and works
     integrator.add_keff_search_control(
-        function=test_function,
+        function=function,
         x0=x0,
         x1=x1,
         bracket=bracket,
@@ -117,9 +114,8 @@ def test_integrator_add_keff_search_control(run_in_tmpdir, model, operator, inte
 
     assert integrator.keff_search_control.x0 == x0
     assert integrator.keff_search_control.x1 == x1
-    assert integrator.keff_search_control.function == test_function
+    assert integrator.keff_search_control.function == function
     assert integrator.keff_search_control.search_kwargs['x_min'] == bracket[0]
     assert integrator.keff_search_control.search_kwargs['x_max'] == bracket[1]
     assert integrator.keff_search_control.search_kwargs['k_tol'] == 0.1
     assert not integrator.keff_search_control.search_kwargs['output']
-    openmc.lib.finalize()

From f8ea4649dfa069804de11e3f6124fae9cd47de76 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 10:24:20 -0500
Subject: [PATCH 04/11] Small edits

---
 openmc/deplete/abc.py                         | 40 +++++++------------
 openmc/deplete/keff_search_control.py         | 23 +----------
 .../test_deplete_keff_search_control.py       |  6 +--
 3 files changed, 20 insertions(+), 49 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index ed0cd695e..b6cc6fe73 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -852,8 +852,7 @@ class Integrator(ABC):
         """Get BOS from keff search control."""
         x = deepcopy(bos_conc)
         # Get new vector after keff criticality control
-        x, keff_search_root = self._keff_search_control.search_for_keff(x, step_index)
-        return x, keff_search_root
+        return self._keff_search_control.search_for_keff(x, step_index)
 
     def integrate(
             self,
@@ -911,10 +910,11 @@ class Integrator(ABC):
                                 "results because no stored keff_search_root is "
                                 "available."
                             )
-                        self._keff_search_control.apply_stored_root(
-                            keff_search_root)
+                        # Apply the control function to the saved root
+                        self._keff_search_control.function(keff_search_root)
                     else:
                         keff_search_root = None
+
                 # Solve Bateman equations over time interval
                 proc_time, n_end = self(n, res.rates, dt, source_rate, i)
 
@@ -1093,42 +1093,32 @@ class Integrator(ABC):
         function: Callable,
         x0: float,
         x1: float,
-        bracket: list[float],
+        bracket: Sequence[float],
         **search_kwargs
     ):
         """Add keff search to the integrator scheme.
 
-        This method creates a :class:`openmc.deplete._KeffSearchControl` that
-        performs keff searches during depletion to maintain a target keff
-        by adjusting a model parameter through the provided function.
+        This method causes OpenMC to perform a keff search during depletion to
+        maintain a target keff by adjusting a model parameter through the
+        provided function.
 
         .. important::
             The function **must** modify the model through ``openmc.lib`` (e.g.,
             ``openmc.lib.cells``, ``openmc.lib.materials``) and **NOT** through
-            ``openmc.model``. The function is called within a
+            ``openmc.Model``. The function is called within a
             :class:`openmc.lib.TemporarySession` context where only the C API
-            (``openmc.lib``) is available for modifications. The function
-            should behave like a setter for the controlled parameter so that a
-            stored keff-search root can be safely reapplied during restart.
+            (``openmc.lib``) is available for modifications.
 
         Parameters
         ----------
         function : Callable
-            Function that modifies the model through ``openmc.lib`` based on a
-            parameter value. The function should take a single float parameter
-            and modify ``openmc.lib`` objects accordingly (e.g., adjust control
-            rod position via ``openmc.lib.cells[...].translation``, material
-            density via ``openmc.lib.materials[...].set_densities(...)``, etc.).
-
-            **Important**: The function must modify ``openmc.lib`` objects, not
-            ``openmc.model`` objects, and should set the controlled parameter
-            directly rather than modifying the current state relative to its
-            existing value.
-        x0: float
+            Function that takes a single float argument and modifies the model
+            through :mod:`openmc.lib`.
+        x0 : float
             Initial lower bound for the keff search.
-        x1: float
+        x1 : float
             Initial upper bound for the keff search.
-        bracket : list[float]
+        bracket : sequence of float
             Bracket interval [x_min, x_max] that constrains the allowed parameter
             values during the keff search. This is a required parameter
             that defines the absolute bounds for the search. The bracket must contain
diff --git a/openmc/deplete/keff_search_control.py b/openmc/deplete/keff_search_control.py
index 08263f348..ab656a4f1 100644
--- a/openmc/deplete/keff_search_control.py
+++ b/openmc/deplete/keff_search_control.py
@@ -59,19 +59,9 @@ class _KeffSearchControl:
             Parameter value that achieves target keff
         """
         root = self._search_for_keff()
-        x = self._update_vec(x)
+        self._update_vec(x)
         return x, root
 
-    def apply_stored_root(self, root: float):
-        """Reapply a previously stored control parameter value.
-
-        Parameters
-        ----------
-        root : float
-            Parameter value from a prior keff search result.
-        """
-        self.function(root)
-
     def _search_for_keff(self) -> float:
         """Perform the keff search using the model's keff_search method.
 
@@ -88,10 +78,7 @@ class _KeffSearchControl:
         with openmc.lib.TemporarySession(self.operator.model):
             # Only pass the first 3 required args plus explicitly provided kwargs
             result = self.operator.model.keff_search(
-                self.function,
-                self.x0,
-                self.x1,
-                **self.search_kwargs
+                self.function, self.x0, self.x1, **self.search_kwargs
             )
         if not result.converged:
             raise ValueError(
@@ -127,10 +114,6 @@ class _KeffSearchControl:
         x : list of numpy.ndarray
             Atom density vector to update (atoms per material)
 
-        Returns
-        -------
-        list of numpy.ndarray
-            Updated rank-local atom density vector
         """
         number = self.operator.number
 
@@ -147,5 +130,3 @@ class _KeffSearchControl:
                 else:
                     atom_density = number.get_atom_density(mat, nuc)
                 x[mat_idx][nuc_idx] = atom_density * volume
-
-        return x
diff --git a/tests/unit_tests/test_deplete_keff_search_control.py b/tests/unit_tests/test_deplete_keff_search_control.py
index 8de4d542c..132f08d1f 100644
--- a/tests/unit_tests/test_deplete_keff_search_control.py
+++ b/tests/unit_tests/test_deplete_keff_search_control.py
@@ -96,9 +96,9 @@ def set_u235_density(u235_density):
 
 
 @pytest.mark.parametrize("function, x0, x1, bracket", [
-    (translate_cell, -1.0, 1.0, [-5.0, 5.0]),
-    (rotate_cell, -45.0, 45.0, [-90.0, 90.0]),
-    (set_u235_density, 0.8, 1.2, [0.5, 1.5])
+    (translate_cell, -1.0, 1.0, (-5.0, 5.0)),
+    (rotate_cell, -45.0, 45.0, (-90.0, 90.0)),
+    (set_u235_density, 0.8, 1.2, (0.5, 1.5))
 ])
 def test_integrator_add_keff_search_control(run_in_tmpdir, model, operator, integrator,
     function, x0, x1, bracket):

From 3b0817063993149a8720ceacf8ff5754fd8f244a Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 10:33:35 -0500
Subject: [PATCH 05/11] Simplify test

---
 .../test_deplete_keff_search_control.py       | 21 +++++++------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/tests/unit_tests/test_deplete_keff_search_control.py b/tests/unit_tests/test_deplete_keff_search_control.py
index 132f08d1f..3c5a80f9a 100644
--- a/tests/unit_tests/test_deplete_keff_search_control.py
+++ b/tests/unit_tests/test_deplete_keff_search_control.py
@@ -11,8 +11,8 @@ from openmc.deplete import CoupledOperator
 
 CHAIN_PATH = Path(__file__).parents[1] / "chain_simple.xml"
 
-@pytest.fixture
-def model():
+
+def make_model():
     f = openmc.Material(name="fuel")
     f.add_element("U", 1, percent_type="ao", enrichment=4.25)
     f.add_element("O", 2)
@@ -60,15 +60,6 @@ def model():
 
     return openmc.Model(geometry, materials, settings)
 
-@pytest.fixture
-def operator(model):
-    return CoupledOperator(model, CHAIN_PATH)
-
-@pytest.fixture
-def integrator(operator):
-    return openmc.deplete.PredictorIntegrator(
-            operator, [1,1], 0.0, timestep_units = 'd')
-
 
 def translate_cell(position):
     """Helper function to translate a cell"""
@@ -100,9 +91,13 @@ def set_u235_density(u235_density):
     (rotate_cell, -45.0, 45.0, (-90.0, 90.0)),
     (set_u235_density, 0.8, 1.2, (0.5, 1.5))
 ])
-def test_integrator_add_keff_search_control(run_in_tmpdir, model, operator, integrator,
-    function, x0, x1, bracket):
+def test_integrator_add_keff_search_control(run_in_tmpdir, function, x0, x1, bracket):
     """Test adding add_keff_search_control to integrator"""
+    model = make_model()
+    operator = CoupledOperator(model, CHAIN_PATH)
+    integrator = openmc.deplete.PredictorIntegrator(
+        operator, [1, 1], 0.0, timestep_units='d')
+
     integrator.add_keff_search_control(
         function=function,
         x0=x0,

From 2b4fa56ca39ffb169945bc817199540dd05d69f0 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 10:53:33 -0500
Subject: [PATCH 06/11] Style fixes

---
 openmc/deplete/abc.py | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index b6cc6fe73..c98b3b2c7 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -1158,7 +1158,7 @@ class Integrator(ABC):
         ...     k_tol=1e-4
         ... )
 
-        Add keff search that sets the U235 density directly:
+        Add keff search that adjusts the U235 density:
 
         >>> def set_u235_density(u235_density):
         ...     # Get the material from openmc.lib
@@ -1181,12 +1181,7 @@ class Integrator(ABC):
 
         """
         self._keff_search_control = _KeffSearchControl(
-            self.operator,
-            function,
-            x0,
-            x1,
-            bracket,
-            **search_kwargs)
+            self.operator, function, x0, x1, bracket, **search_kwargs)
 
 @add_params
 class SIIntegrator(Integrator):

From deb9f1d79a65f60deb851320f555e662f6febd2b Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 11:05:59 -0500
Subject: [PATCH 07/11] Refactor Integrator.integrate

---
 openmc/deplete/abc.py | 63 +++++++++++++++++++++++++------------------
 1 file changed, 37 insertions(+), 26 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index c98b3b2c7..8ba083b58 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -848,12 +848,43 @@ class Integrator(ABC):
         return (self.operator.prev_res[-1].time[0],
                 len(self.operator.prev_res) - 1)
 
-    def _get_bos_from_keff_search_control(self, step_index, bos_conc):
-        """Get BOS from keff search control."""
+    def _apply_keff_search_control(self, step_index, bos_conc):
+        """Apply keff search control to beginning-of-step concentrations."""
         x = deepcopy(bos_conc)
-        # Get new vector after keff criticality control
         return self._keff_search_control.search_for_keff(x, step_index)
 
+    def _restore_keff_search_control(self, res):
+        """Restore keff search control from restart results."""
+        keff_search_root = res.keff_search_root
+        if keff_search_root is None:
+            raise ValueError(
+                "Cannot restore keff search control from restart "
+                "results because no stored keff_search_root is "
+                "available."
+            )
+        self._keff_search_control.function(keff_search_root)
+        return keff_search_root
+
+    def _get_bos_data(self, step_index, source_rate, bos_conc):
+        """Get beginning-of-step concentrations, rates, and control state."""
+        if step_index > 0 or self.operator.prev_res is None:
+            if self._keff_search_control is not None and source_rate != 0.0:
+                bos_conc, keff_search_root = self._apply_keff_search_control(
+                    step_index, bos_conc)
+            else:
+                keff_search_root = None
+            bos_conc, res = self._get_bos_data_from_operator(
+                step_index, source_rate, bos_conc)
+        else:
+            bos_conc, res = self._get_bos_data_from_restart(
+                source_rate, bos_conc)
+            if self._keff_search_control is not None and source_rate != 0.0:
+                keff_search_root = self._restore_keff_search_control(res)
+            else:
+                keff_search_root = None
+
+        return bos_conc, res, keff_search_root
+
     def integrate(
             self,
             final_step: bool = True,
@@ -892,28 +923,8 @@ class Integrator(ABC):
                 if output and comm.rank == 0:
                     print(f"[openmc.deplete] t={t} s, dt={dt} s, source={source_rate}")
 
-                # Solve transport equation (or obtain result from restart)
-                if i > 0 or self.operator.prev_res is None:
-                    # Update geometry/material according to keff search control
-                    if self._keff_search_control is not None and source_rate != 0.0:
-                        n, keff_search_root = self._get_bos_from_keff_search_control(i, n)
-                    else:
-                        keff_search_root = None
-                    n, res = self._get_bos_data_from_operator(i, source_rate, n)
-                else:
-                    n, res = self._get_bos_data_from_restart(source_rate, n)
-                    if self._keff_search_control is not None and source_rate != 0.0:
-                        keff_search_root = res.keff_search_root
-                        if keff_search_root is None:
-                            raise ValueError(
-                                "Cannot restore keff search control from restart "
-                                "results because no stored keff_search_root is "
-                                "available."
-                            )
-                        # Apply the control function to the saved root
-                        self._keff_search_control.function(keff_search_root)
-                    else:
-                        keff_search_root = None
+                # Get beginning-of-step data from operator or restart results
+                n, res, keff_search_root = self._get_bos_data(i, source_rate, n)
 
                 # Solve Bateman equations over time interval
                 proc_time, n_end = self(n, res.rates, dt, source_rate, i)
@@ -942,7 +953,7 @@ class Integrator(ABC):
             if output and final_step and comm.rank == 0:
                 print(f"[openmc.deplete] t={t} (final operator evaluation)")
             if self._keff_search_control is not None and source_rate != 0.0:
-                n, keff_search_root = self._get_bos_from_keff_search_control(i+1, n)
+                n, keff_search_root = self._apply_keff_search_control(i + 1, n)
             else:
                 keff_search_root = None
             res_final = self.operator(n, source_rate if final_step else 0.0)

From 7ac6fcdcc34d39dce7bc1b8a4008d60f1c082559 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 11:09:05 -0500
Subject: [PATCH 08/11] Remove step_index in search_for_keff calls

---
 openmc/deplete/abc.py                 | 8 ++++----
 openmc/deplete/keff_search_control.py | 4 +---
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index 8ba083b58..2b31bd3a3 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -848,10 +848,10 @@ class Integrator(ABC):
         return (self.operator.prev_res[-1].time[0],
                 len(self.operator.prev_res) - 1)
 
-    def _apply_keff_search_control(self, step_index, bos_conc):
+    def _apply_keff_search_control(self, bos_conc):
         """Apply keff search control to beginning-of-step concentrations."""
         x = deepcopy(bos_conc)
-        return self._keff_search_control.search_for_keff(x, step_index)
+        return self._keff_search_control.search_for_keff(x)
 
     def _restore_keff_search_control(self, res):
         """Restore keff search control from restart results."""
@@ -870,7 +870,7 @@ class Integrator(ABC):
         if step_index > 0 or self.operator.prev_res is None:
             if self._keff_search_control is not None and source_rate != 0.0:
                 bos_conc, keff_search_root = self._apply_keff_search_control(
-                    step_index, bos_conc)
+                    bos_conc)
             else:
                 keff_search_root = None
             bos_conc, res = self._get_bos_data_from_operator(
@@ -953,7 +953,7 @@ class Integrator(ABC):
             if output and final_step and comm.rank == 0:
                 print(f"[openmc.deplete] t={t} (final operator evaluation)")
             if self._keff_search_control is not None and source_rate != 0.0:
-                n, keff_search_root = self._apply_keff_search_control(i + 1, n)
+                n, keff_search_root = self._apply_keff_search_control(n)
             else:
                 keff_search_root = None
             res_final = self.operator(n, source_rate if final_step else 0.0)
diff --git a/openmc/deplete/keff_search_control.py b/openmc/deplete/keff_search_control.py
index ab656a4f1..8837dda3a 100644
--- a/openmc/deplete/keff_search_control.py
+++ b/openmc/deplete/keff_search_control.py
@@ -41,15 +41,13 @@ class _KeffSearchControl:
         self.search_kwargs['x_min'] = bracket[0]
         self.search_kwargs['x_max'] = bracket[1]
 
-    def search_for_keff(self, x, step_index):
+    def search_for_keff(self, x):
         """Perform keff search and update the atom density vector.
 
         Parameters
         ----------
         x : list of numpy.ndarray
             Current atom density vector (atoms per material)
-        step_index : int
-            Current depletion step index
 
         Returns
         -------

From 95dbb29c2103e46116ae523f3e564093583e6a34 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 11:15:18 -0500
Subject: [PATCH 09/11] Remove a deepcopy

---
 openmc/deplete/abc.py                 | 9 ++-------
 openmc/deplete/keff_search_control.py | 2 +-
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index 2b31bd3a3..00a84a0ec 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -848,11 +848,6 @@ class Integrator(ABC):
         return (self.operator.prev_res[-1].time[0],
                 len(self.operator.prev_res) - 1)
 
-    def _apply_keff_search_control(self, bos_conc):
-        """Apply keff search control to beginning-of-step concentrations."""
-        x = deepcopy(bos_conc)
-        return self._keff_search_control.search_for_keff(x)
-
     def _restore_keff_search_control(self, res):
         """Restore keff search control from restart results."""
         keff_search_root = res.keff_search_root
@@ -869,7 +864,7 @@ class Integrator(ABC):
         """Get beginning-of-step concentrations, rates, and control state."""
         if step_index > 0 or self.operator.prev_res is None:
             if self._keff_search_control is not None and source_rate != 0.0:
-                bos_conc, keff_search_root = self._apply_keff_search_control(
+                keff_search_root = self._keff_search_control.search_for_keff(
                     bos_conc)
             else:
                 keff_search_root = None
@@ -953,7 +948,7 @@ class Integrator(ABC):
             if output and final_step and comm.rank == 0:
                 print(f"[openmc.deplete] t={t} (final operator evaluation)")
             if self._keff_search_control is not None and source_rate != 0.0:
-                n, keff_search_root = self._apply_keff_search_control(n)
+                keff_search_root = self._keff_search_control.search_for_keff(n)
             else:
                 keff_search_root = None
             res_final = self.operator(n, source_rate if final_step else 0.0)
diff --git a/openmc/deplete/keff_search_control.py b/openmc/deplete/keff_search_control.py
index 8837dda3a..b8bc06793 100644
--- a/openmc/deplete/keff_search_control.py
+++ b/openmc/deplete/keff_search_control.py
@@ -58,7 +58,7 @@ class _KeffSearchControl:
         """
         root = self._search_for_keff()
         self._update_vec(x)
-        return x, root
+        return root
 
     def _search_for_keff(self) -> float:
         """Perform the keff search using the model's keff_search method.

From 69c3483687d6c2ceab4306592e2e23eaf86c3de2 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 11:47:32 -0500
Subject: [PATCH 10/11] Rename to run

---
 openmc/deplete/abc.py                 | 5 ++---
 openmc/deplete/keff_search_control.py | 4 +---
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index 00a84a0ec..c149919b1 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -864,8 +864,7 @@ class Integrator(ABC):
         """Get beginning-of-step concentrations, rates, and control state."""
         if step_index > 0 or self.operator.prev_res is None:
             if self._keff_search_control is not None and source_rate != 0.0:
-                keff_search_root = self._keff_search_control.search_for_keff(
-                    bos_conc)
+                keff_search_root = self._keff_search_control.run(bos_conc)
             else:
                 keff_search_root = None
             bos_conc, res = self._get_bos_data_from_operator(
@@ -948,7 +947,7 @@ class Integrator(ABC):
             if output and final_step and comm.rank == 0:
                 print(f"[openmc.deplete] t={t} (final operator evaluation)")
             if self._keff_search_control is not None and source_rate != 0.0:
-                keff_search_root = self._keff_search_control.search_for_keff(n)
+                keff_search_root = self._keff_search_control.run(n)
             else:
                 keff_search_root = None
             res_final = self.operator(n, source_rate if final_step else 0.0)
diff --git a/openmc/deplete/keff_search_control.py b/openmc/deplete/keff_search_control.py
index b8bc06793..49f7cc4df 100644
--- a/openmc/deplete/keff_search_control.py
+++ b/openmc/deplete/keff_search_control.py
@@ -41,7 +41,7 @@ class _KeffSearchControl:
         self.search_kwargs['x_min'] = bracket[0]
         self.search_kwargs['x_max'] = bracket[1]
 
-    def search_for_keff(self, x):
+    def run(self, x):
         """Perform keff search and update the atom density vector.
 
         Parameters
@@ -51,8 +51,6 @@ class _KeffSearchControl:
 
         Returns
         -------
-        x : list of numpy.ndarray
-            Updated atom density vector
         root : float
             Parameter value that achieves target keff
         """

From 84e7422aa3a1d5771056681c975b0a536f776378 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Thu, 12 Mar 2026 11:50:13 -0500
Subject: [PATCH 11/11] Don't expose keff_search_control

---
 openmc/deplete/abc.py                              |  9 ---------
 .../unit_tests/test_deplete_keff_search_control.py | 14 +++++++-------
 2 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/openmc/deplete/abc.py b/openmc/deplete/abc.py
index c149919b1..b5cea425c 100644
--- a/openmc/deplete/abc.py
+++ b/openmc/deplete/abc.py
@@ -731,15 +731,6 @@ class Integrator(ABC):
 
         self._solver = func
 
-    @property
-    def keff_search_control(self):
-        return self._keff_search_control
-
-    @keff_search_control.setter
-    def keff_search_control(self, keff_search_control):
-        check_type('keff search control', keff_search_control, _KeffSearchControl)
-        self._keff_search_control = keff_search_control
-
     def _timed_deplete(self, n, rates, dt, i=None, matrix_func=None):
         start = time.time()
         results = deplete(
diff --git a/tests/unit_tests/test_deplete_keff_search_control.py b/tests/unit_tests/test_deplete_keff_search_control.py
index 3c5a80f9a..425b8f840 100644
--- a/tests/unit_tests/test_deplete_keff_search_control.py
+++ b/tests/unit_tests/test_deplete_keff_search_control.py
@@ -107,10 +107,10 @@ def test_integrator_add_keff_search_control(run_in_tmpdir, function, x0, x1, bra
         output=False,
     )
 
-    assert integrator.keff_search_control.x0 == x0
-    assert integrator.keff_search_control.x1 == x1
-    assert integrator.keff_search_control.function == function
-    assert integrator.keff_search_control.search_kwargs['x_min'] == bracket[0]
-    assert integrator.keff_search_control.search_kwargs['x_max'] == bracket[1]
-    assert integrator.keff_search_control.search_kwargs['k_tol'] == 0.1
-    assert not integrator.keff_search_control.search_kwargs['output']
+    assert integrator._keff_search_control.x0 == x0
+    assert integrator._keff_search_control.x1 == x1
+    assert integrator._keff_search_control.function == function
+    assert integrator._keff_search_control.search_kwargs['x_min'] == bracket[0]
+    assert integrator._keff_search_control.search_kwargs['x_max'] == bracket[1]
+    assert integrator._keff_search_control.search_kwargs['k_tol'] == 0.1
+    assert not integrator._keff_search_control.search_kwargs['output']