I also mentioned this here but the problem is the recent change in Factorio mechanics. If an item exceeds its stack limit (like 100 solar panels in a satellite, but only stack size of 50) then it can't be uncrafted/recycled in a smelting machine anymore, regardless of the number of actual slots.
I think the reactor requires like 500 concrete, but concrete only stacks to 100, so it falls to the same problem. Without increasing the stack size, or decreasing the cost of these items, there's no way to make them work. And removing them from the "recycle-able" list is... annoying at best, since both of our mods use automated processes to reverse all recipes. Personally I don't think it's an issue worth fixing, but The_Evil_Pickle might think otherwise.
