diff --git a/basis/lib.lua b/basis/lib.lua
index d47f5ac..6bf49dc 100644
--- a/basis/lib.lua
+++ b/basis/lib.lua
@@ -244,6 +244,17 @@ function techage.add_to_set(set, x)
 	end
 end
 
+-- techage.tbl_filter({"a", "b", "c", "d"}, function(v, k, t) return v >= "c" end)  --> {"c","d"}
+techage.tbl_filter = function(t, filterIter)
+	local out = {}
+
+	for k, v in pairs(t) do
+		if filterIter(v, k, t) then out[k] = v end
+	end
+
+	return out
+end
+
 function techage.get_node_lvm(pos)
 	local node = minetest.get_node_or_nil(pos)
 	if node then
diff --git a/fusion_reactor/controller.lua b/fusion_reactor/controller.lua
index 848cdaf..8af0bd8 100644
--- a/fusion_reactor/controller.lua
+++ b/fusion_reactor/controller.lua
@@ -46,6 +46,7 @@ local function count_trues(t)
 end
 
 local function nucleus(t)
+	t = techage.tbl_filter(t, function(v, k, t) return type(v) == "table" end)
 	if #t == 4 then
 		if vector.equals(t[1], t[2]) and vector.equals(t[3], t[4]) then
 			return true