diff --git a/src/physics.cpp b/src/physics.cpp
index f640fa1e0b..aedb6c1df9 100644
--- a/src/physics.cpp
+++ b/src/physics.cpp
@@ -184,7 +184,7 @@ create_fission_sites(Particle* p, int i_nuclide, const Reaction* rx)
     Particle::Bank* site;
     if(use_fission_bank)
     {
-      int idx;
+      int64_t idx;
       #pragma omp atomic capture
       idx = simulation::fission_bank_length++;
       if( idx >= simulation::fission_bank_max )
diff --git a/src/physics_mg.cpp b/src/physics_mg.cpp
index 4abce9397a..390ee41e7d 100644
--- a/src/physics_mg.cpp
+++ b/src/physics_mg.cpp
@@ -109,7 +109,6 @@ create_fission_sites(Particle* p)
   // Begin banking the source neutrons
   // First, if our bank is full then don't continue
   if (nu == 0) return;
-  
 
   // Initialize the counter of delayed neutrons encountered for each delayed
   // group.
@@ -131,7 +130,7 @@ create_fission_sites(Particle* p)
     Particle::Bank* site;
     if(use_fission_bank)
     {
-      int idx;
+      int64_t idx;
       #pragma omp atomic capture
       idx = simulation::fission_bank_length++;
       if( idx >= simulation::fission_bank_max )
diff --git a/src/simulation.cpp b/src/simulation.cpp
index d0f7e387d1..a3b586a638 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -394,7 +394,9 @@ void finalize_generation()
   global_tally_leakage = 0.0;
 
   if (settings::run_mode == RUN_MODE_EIGENVALUE) {	
-    // If using shared memory, sort the fission bank so as to allow for reproducibility
+    // If using shared memory, stable sort the fission bank (by parent IDs) 
+    // so as to allow for reproducibility regardless of which order particles
+    // are run in.
     #ifdef _OPENMP
     std::stable_sort(simulation::fission_bank,
         simulation::fission_bank + simulation::fission_bank_length);
@@ -558,7 +560,7 @@ void free_memory_simulation()
 
 void transport_history_based_single_particle(Particle& p)
 {
-  while(true) {
+  while (true) {
     p.event_calculate_xs();
     p.event_advance();
     if( p.collision_distance_ > p.boundary_.distance ) 
diff --git a/src/tallies/derivative.cpp b/src/tallies/derivative.cpp
index 09662b6790..76ae314cc8 100644
--- a/src/tallies/derivative.cpp
+++ b/src/tallies/derivative.cpp
@@ -115,8 +115,8 @@ apply_derivative_to_score(const Particle* p, int i_tally, int i_nuclide,
   // where (1/f * d_f/d_p) is the (logarithmic) flux derivative and p is the
   // perturbated variable.
 
-  const auto& deriv = model::tally_derivs[tally.deriv_];
-  const auto& flux_deriv = p->flux_derivs_[tally.deriv_];
+  const auto& deriv {model::tally_derivs[tally.deriv_]};
+  const auto flux_deriv = p->flux_derivs_[tally.deriv_];
 
   // Handle special cases where we know that d_c/d_p must be zero.
   if (score_bin == SCORE_FLUX) {
@@ -618,8 +618,7 @@ void score_collision_derivative(Particle* p)
 
   const Material& material {*model::materials[p->material_]};
 
-  //for (auto& deriv : model::tally_derivs) {
-  for (int idx = 0; idx < model::tally_derivs.size(); idx++) {
+  for (auto idx = 0; idx < model::tally_derivs.size(); idx++) {
     const auto& deriv = model::tally_derivs[idx];
     auto& flux_deriv = p->flux_derivs_[idx];
 
diff --git a/src/track_output.cpp b/src/track_output.cpp
index 748492a96e..5e071be01b 100644
--- a/src/track_output.cpp
+++ b/src/track_output.cpp
@@ -52,7 +52,7 @@ void finalize_particle_track(Particle& p)
     write_attribute(file_id, "version", VERSION_TRACK);
     write_attribute(file_id, "n_particles", p.tracks_.size());
     write_attribute(file_id, "n_coords", n_coords);
-    for (int i = 1; i <= p.tracks_.size(); ++i) {
+    for (auto i = 1; i <= p.tracks_.size(); ++i) {
       const auto& t {p.tracks_[i-1]};
       size_t n = t.size();
       xt::xtensor<double, 2> data({n,3});