diff --git a/src/ace.F90 b/src/ace.F90
index c12915c4b1..b3dbd5adda 100644
--- a/src/ace.F90
+++ b/src/ace.F90
@@ -577,7 +577,7 @@ contains
     rxn % MT            = 2
     rxn % Q_value       = ZERO
     rxn % multiplicity  = 1
-    rxn % IE            = 1
+    rxn % threshold     = 1
     rxn % scatter_in_cm = .true.
     rxn % has_angle_dist = .false.
     rxn % has_energy_dist = .false.
@@ -608,7 +608,7 @@ contains
        ! read starting energy index
        LOCA = int(XSS(LXS + i - 1))
        IE   = int(XSS(JXS7 + LOCA - 1))
-       rxn % IE = IE
+       rxn % threshold = IE
 
        ! read number of energies cross section values
        NE = int(XSS(JXS7 + LOCA))
diff --git a/src/ace_header.F90 b/src/ace_header.F90
index ccc438fca0..a1769733b3 100644
--- a/src/ace_header.F90
+++ b/src/ace_header.F90
@@ -42,7 +42,7 @@ module ace_header
      integer :: MT                      ! ENDF MT value
      real(8) :: Q_value                 ! Reaction Q value
      integer :: multiplicity            ! Number of secondary particles released
-     integer :: IE                      ! Starting energy grid index
+     integer :: threshold               ! Energy grid index of threshold
      logical :: scatter_in_cm           ! scattering system in center-of-mass?
      real(8), allocatable :: sigma(:)   ! Cross section values
      logical :: has_angle_dist          ! Angle distribution present?
diff --git a/src/cross_section.F90 b/src/cross_section.F90
index ae7e4ce8a6..0fbe2c3843 100644
--- a/src/cross_section.F90
+++ b/src/cross_section.F90
@@ -379,9 +379,9 @@ contains
        f = micro_xs(index_nuclide) % interp_factor
 
        ! Determine inelastic scattering cross section
-       if (i_energy >= rxn % IE) then
-          inelastic = (ONE - f) * rxn % sigma(i_energy - rxn%IE + 1) + &
-               f * rxn % sigma(i_energy - rxn%IE + 2)
+       if (i_energy >= rxn % threshold) then
+          inelastic = (ONE - f) * rxn % sigma(i_energy - rxn%threshold + 1) + &
+               f * rxn % sigma(i_energy - rxn%threshold + 2)
        end if
     end if
 
diff --git a/src/output.F90 b/src/output.F90
index 60ef42a258..9372845243 100644
--- a/src/output.F90
+++ b/src/output.F90
@@ -288,7 +288,7 @@ contains
     write(ou,*) '    MT = ' // to_str(rxn % MT)
     write(ou,*) '    Q-value = ' // to_str(rxn % Q_value)
     write(ou,*) '    Multiplicity = ' // to_str(rxn % multiplicity)
-    write(ou,*) '    Starting index = ' // to_str(rxn % IE)
+    write(ou,*) '    Threshold = ' // to_str(rxn % threshold)
     if (rxn % has_energy_dist) then
        write(ou,*) '    Energy: Law ' // to_str(rxn % edist % law)
     end if
@@ -840,10 +840,10 @@ contains
 
        write(unit_,'(3X,A11,1X,F8.3,3X,L1,3X,A4,1X,I6,1X,I11,1X,I11)') &
             reaction_name(rxn % MT), rxn % Q_value, rxn % scatter_in_cm, &
-            law, rxn % IE, size_angle, size_energy
+            law, rxn % threshold, size_angle, size_energy
 
        ! Accumulate data size
-       size_xs = size_xs + (nuc % n_grid - rxn%IE + 1) * 8
+       size_xs = size_xs + (nuc % n_grid - rxn%threshold + 1) * 8
        size_angle_total = size_angle_total + size_angle
        size_energy_total = size_energy_total + size_energy
     end do
diff --git a/src/physics.F90 b/src/physics.F90
index 4bf582e866..501078d63b 100644
--- a/src/physics.F90
+++ b/src/physics.F90
@@ -365,12 +365,12 @@ contains
              rxn => nuc % reactions(nuc % index_fission(i))
 
              ! if energy is below threshold for this reaction, skip it
-             if (IE < rxn%IE) cycle
+             if (IE < rxn % threshold) cycle
 
              ! add to cumulative probability
              if (nuc % has_partial_fission) then
-                prob = prob + ((ONE-f)*rxn%sigma(IE-rxn%IE+1) & 
-                     + f*(rxn%sigma(IE-rxn%IE+2)))
+                prob = prob + ((ONE - f)*rxn%sigma(IE - rxn%threshold + 1) & 
+                     + f*(rxn%sigma(IE - rxn%threshold + 2)))
              else
                 prob = prob + micro_xs(index_nuclide) % fission
              end if
@@ -469,11 +469,11 @@ contains
           if (rxn%MT >= 200 .or. rxn%MT == N_LEVEL) cycle
           
           ! if energy is below threshold for this reaction, skip it
-          if (IE < rxn%IE) cycle
+          if (IE < rxn % threshold) cycle
 
           ! add to cumulative probability
-          prob = prob + ((ONE-f)*rxn%sigma(IE-rxn%IE+1) & 
-               + f*(rxn%sigma(IE-rxn%IE+2)))
+          prob = prob + ((ONE - f)*rxn%sigma(IE - rxn%threshold + 1) & 
+               + f*(rxn%sigma(IE - rxn%threshold + 2)))
        end do
 
        ! Perform collision physics for inelastics scattering