diff --git a/src/main/java/gregtech/api/nuclear/fission/FissionReactor.java b/src/main/java/gregtech/api/nuclear/fission/FissionReactor.java
index 23692a50d3d..79b33079028 100644
--- a/src/main/java/gregtech/api/nuclear/fission/FissionReactor.java
+++ b/src/main/java/gregtech/api/nuclear/fission/FissionReactor.java
@@ -243,19 +243,18 @@ public void computeGeometry() {
                  * Geometric factor calculation is done by (rough) numerical integration along a straight path between
                  * the two cells
                  */
+                int prevX = fuelRods.get(i).getX();
+                int prevY = fuelRods.get(i).getY();
                 double resolution = ConfigHolder.machines.nuclear.fissionReactorResolution;
                 for (int t = 0; t < resolution; t++) {
-                    double x;
-                    double y;
-
-                    x = (rodTwo.getX() - rodOne.getX()) *
-                            ((float) t / resolution) + fuelRods.get(i).getX();
-                    y = (rodTwo.getY() - rodOne.getY()) *
-                            ((float) t / resolution) + fuelRods.get(i).getY();
+                    int x = (int) Math.round((rodTwo.getX() - rodOne.getX()) *
+                            ((float) t / resolution) + fuelRods.get(i).getX());
+                    int y = (int) Math.round((rodTwo.getY() - rodOne.getY()) *
+                            ((float) t / resolution) + fuelRods.get(i).getY());
                     if (x < 0 || x > reactorLayout.length - 1 || y < 0 || y > reactorLayout.length - 1) {
                         continue;
                     }
-                    ReactorComponent component = reactorLayout[(int) Math.round(x)][(int) Math.round(y)];
+                    ReactorComponent component = reactorLayout[x][y];
 
                     if (component == null) {
                         continue;
@@ -263,6 +262,12 @@ public void computeGeometry() {
 
                     mij += component.getModerationFactor();
 
+                    if (x == prevX && y == prevY) {
+                        continue;
+                    }
+                    prevX = x;
+                    prevY = y;
+
                     /*
                      * For simplicity, we pretend that fuel rods are completely opaque to neutrons, paths that hit fuel
                      * rods are ignored as obstructed
diff --git a/src/main/java/gregtech/common/metatileentities/multi/MetaTileEntityFissionReactor.java b/src/main/java/gregtech/common/metatileentities/multi/MetaTileEntityFissionReactor.java
index 72d6494aff3..c8509db454b 100644
--- a/src/main/java/gregtech/common/metatileentities/multi/MetaTileEntityFissionReactor.java
+++ b/src/main/java/gregtech/common/metatileentities/multi/MetaTileEntityFissionReactor.java
@@ -325,11 +325,12 @@ protected EnumFacing getRight() {
     /**
      * Uses the upper layer to determine the diameter of the structure
      */
-    protected int findDiameter() {
+    protected int findDiameter(int heightTop) {
         int i = 1;
         BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos(this.getPos());
+        pos.move(getUp(), heightTop);
         while (i <= 15) {
-            if (this.isBlockEdge(this.getWorld(), pos.move(getUp()),
+            if (this.isBlockEdge(this.getWorld(), pos,
                     this.getFrontFacing().getOpposite(),
                     i))
                 break;
@@ -482,7 +483,7 @@ protected BlockPattern createStructurePattern() {
 
         this.height = heightTop + heightBottom + 1;
 
-        this.diameter = this.getWorld() != null ? Math.max(Math.min(this.findDiameter(), 15), 5) : 5;
+        this.diameter = this.getWorld() != null ? Math.max(Math.min(this.findDiameter(heightTop), 15), 5) : 5;
 
         int radius = this.diameter % 2 == 0 ? (int) Math.floor(this.diameter / 2.f) :
                 Math.round((this.diameter - 1) / 2.f);
diff --git a/src/main/resources/assets/gregtech/lang/en_us.lang b/src/main/resources/assets/gregtech/lang/en_us.lang
index b4320c5ceea..8d5152733c7 100644
--- a/src/main/resources/assets/gregtech/lang/en_us.lang
+++ b/src/main/resources/assets/gregtech/lang/en_us.lang
@@ -1616,8 +1616,9 @@ gregtech.material.palladium=Palladium
 gregtech.material.phosphorus=Phosphorus
 gregtech.material.polonium=Polonium
 gregtech.material.platinum=Platinum
+gregtech.material.plutonium=Plutonium
 gregtech.material.plutonium_238=Plutonium 238
-gregtech.material.plutonium=Plutonium 239
+gregtech.material.plutonium_239=Plutonium 239
 gregtech.material.plutonium_240=Plutonium 240
 gregtech.material.plutonium_241=Plutonium 241
 gregtech.material.plutonium_242=Plutonium 242