diff --git a/include/openmc/nuclide.h b/include/openmc/nuclide.h
index e3d43450d..db30a1a50 100644
--- a/include/openmc/nuclide.h
+++ b/include/openmc/nuclide.h
@@ -14,11 +14,15 @@ namespace openmc {
 // Global variables
 //==============================================================================
 
+namespace data {
+
 // Minimum/maximum transport energy for each particle type. Order corresponds to
 // that of the ParticleType enum
 extern std::array<double, 2> energy_min;
 extern std::array<double, 2> energy_max;
 
+} // namespace data
+
 //===============================================================================
 //! Cached microscopic cross sections for a particular nuclide at the current
 //! energy
diff --git a/src/finalize.cpp b/src/finalize.cpp
index 7439e7bdb..5885470c1 100644
--- a/src/finalize.cpp
+++ b/src/finalize.cpp
@@ -75,8 +75,8 @@ int openmc_finalize()
   simulation::satisfy_triggers = false;
   simulation::total_gen = 0;
 
-  energy_max = {INFTY, INFTY};
-  energy_min = {0.0, 0.0};
+  data::energy_max = {INFTY, INFTY};
+  data::energy_min = {0.0, 0.0};
   n_tallies = 0;
   model::root_universe = -1;
   openmc_set_seed(DEFAULT_SEED);
diff --git a/src/nuclide.cpp b/src/nuclide.cpp
index 79e2289ae..18e7e5a7e 100644
--- a/src/nuclide.cpp
+++ b/src/nuclide.cpp
@@ -6,9 +6,13 @@ namespace openmc {
 // Global variables
 //==============================================================================
 
+namespace data {
+
 std::array<double, 2> energy_min {0.0, 0.0};
 std::array<double, 2> energy_max {INFTY, INFTY};
 
+} // namespace data
+
 //==============================================================================
 // Fortran compatibility functions
 //==============================================================================
@@ -16,8 +20,8 @@ std::array<double, 2> energy_max {INFTY, INFTY};
 extern "C" void
 set_particle_energy_bounds(int particle, double E_min, double E_max)
 {
-  energy_min[particle - 1] = E_min;
-  energy_max[particle - 1] = E_max;
+  data::energy_min[particle - 1] = E_min;
+  data::energy_max[particle - 1] = E_max;
 }
 
 } // namespace openmc
diff --git a/src/source.cpp b/src/source.cpp
index 80bafe945..1cb844ec9 100644
--- a/src/source.cpp
+++ b/src/source.cpp
@@ -207,10 +207,10 @@ Bank SourceDistribution::sample() const
   auto energy_ptr = dynamic_cast<Discrete*>(energy_.get());
   if (energy_ptr) {
     auto energies = xt::adapt(energy_ptr->x());
-    if (xt::any(energies > energy_max[p-1])) {
+    if (xt::any(energies > data::energy_max[p-1])) {
       fatal_error("Source energy above range of energies of at least "
                   "one cross section table");
-    } else if (xt::any(energies < energy_min[p-1])) {
+    } else if (xt::any(energies < data::energy_min[p-1])) {
       fatal_error("Source energy below range of energies of at least "
                   "one cross section table");
     }
@@ -221,7 +221,7 @@ Bank SourceDistribution::sample() const
     site.E = energy_->sample();
 
     // Resample if energy falls outside minimum or maximum particle energy
-    if (site.E < energy_max[p-1] && site.E > energy_min[p-1]) break;
+    if (site.E < data::energy_max[p-1] && site.E > data::energy_min[p-1]) break;
   }
 
   // Set delayed group