diff --git a/openmc/deplete/helpers.py b/openmc/deplete/helpers.py
index 8f35fac433..ac81d0ac7a 100644
--- a/openmc/deplete/helpers.py
+++ b/openmc/deplete/helpers.py
@@ -163,7 +163,7 @@ class FissionYieldHelper(object):
 
     Parameters
     ----------
-    chain_nuclides : iterable of openmc.deplete.nuclide
+    chain_nuclides : iterable of openmc.deplete.Nuclide
         Nuclides tracked in the depletion chain. Not necessary
         that all have yield data.
     n_bmats : int
@@ -176,15 +176,9 @@ class FissionYieldHelper(object):
     results : numpy.ndarray
         Array of tally results for this process with shape
         ``(n_local_mat, n_energy, n_nucs)``
-    libraries : list of dict
-        List of fission yield dictionaries of the form
-        ``{parent: {product: yield}}``. Populated in
-        :meth:`compute_yields` and reset during
-        :meth:`unpack`.
     """
 
     def __init__(self, chain_nuclides, n_bmats):
-        self.libraries = []
         self._chain_nuclides = {}
         self._chain_set = set()
         self._tally_map = {}
@@ -245,7 +239,7 @@ class FissionYieldHelper(object):
         Parameters
         ----------
         nuclides : iterable of str
-            nuclides with non-zero densities that are candidates
+            Nuclides with non-zero densities that are candidates
             for the fission tally. Not necessary that all are nuclides
             with fission yields, but at least one must be
 
@@ -275,9 +269,6 @@ class FissionYieldHelper(object):
 
     def unpack(self):
         """Unpack fission rate tallies to produce :attr:`results`
-
-        Resets :attr:`libraries` under the assumption this is called
-        during the :class:`openmc.deplete.Operator` unpacking process
         """
         # if this process is not responsible for depleting anything
         # [more processes than burnable materials]
@@ -285,9 +276,6 @@ class FissionYieldHelper(object):
         if self.local_indexes.size == 0:
             return
 
-        # clear old libraries
-        self.libraries = []
-
         # get view into tally results
         # new shape: [material, energy, parent nuclide]
         result_view = self._reaction_tally.results[..., 1].reshape(
@@ -312,7 +300,7 @@ class FissionYieldHelper(object):
     def compute_yields(self, local_mat_index):
         """Compute single fission yields using :attr:`results`
 
-        Produces a new library in :attr:`self.libraries`
+        Produces a new library in :attr:`libraries`
 
         Parameters
         ----------
@@ -320,6 +308,11 @@ class FissionYieldHelper(object):
             Index for material tracked on this process that
             exists in :attr:`local_mat_index` and fits within
             the first axis in :attr:`results`
+
+        Returns
+        -------
+        library : dict
+            Dictionary of ``{parent: {product: fyield}}``
         """
         tally_results = self.results[local_mat_index]
 
@@ -337,9 +330,8 @@ class FissionYieldHelper(object):
                 initial_library[parent] += yield_data * fiss_frac
 
         # convert to dictionary that can be passed to Chain.form_matrix
-        # {parent: {product: yield}}
         library = {}
         for k, yield_obj in initial_library.items():
             library[k.name] = dict(zip(yield_obj.products, yield_obj.yields))
 
-        self.libraries.append(library)
+        return library
diff --git a/openmc/deplete/operator.py b/openmc/deplete/operator.py
index 0c8c72987b..d99c96f185 100644
--- a/openmc/deplete/operator.py
+++ b/openmc/deplete/operator.py
@@ -565,6 +565,9 @@ class Operator(TransportOperator):
         self._energy_helper.reset()
         self._fsn_yield_helper.unpack()
 
+        # Store fission yield dictionaries
+        fission_yields = []
+
         # Create arrays to store fission Q values, reaction rates, and nuclide
         # numbers, zeroed out in material iteration
         number = np.empty(rates.n_nuc)
@@ -587,7 +590,7 @@ class Operator(TransportOperator):
                 mat_index, nuc_ind, react_ind)
 
             # Compute fission yields for this material
-            self._fsn_yield_helper.compute_yields(i)
+            fission_yields.append(self._fsn_yield_helper.compute_yields(i))
 
             # Accumulate energy from fission
             self._energy_helper.update(tally_rates[:, fission_ind], mat_index)
@@ -603,7 +606,7 @@ class Operator(TransportOperator):
         rates *= power / energy
 
         # Store new fission yields on the chain
-        self.chain.fission_yields = self._fsn_yield_helper.libraries
+        self.chain.fission_yields = fission_yields
 
         return OperatorResult(k_combined, rates)
 
diff --git a/tests/unit_tests/test_deplete_helpers.py b/tests/unit_tests/test_deplete_helpers.py
index 5db979098b..15ae1550ed 100644
--- a/tests/unit_tests/test_deplete_helpers.py
+++ b/tests/unit_tests/test_deplete_helpers.py
@@ -91,9 +91,6 @@ def test_fission_yield_helper():
         }
     }
 
-    assert len(helper.libraries) == 0
-    helper.compute_yields(0)
-    assert len(helper.libraries) == 1
-    act_library = helper.libraries[0]
+    act_library = helper.compute_yields(0)
     for parent, sub_yields in exp_lib.items():
         assert act_library[parent] == pytest.approx(sub_yields)