Tiny Pile of Uranium-235 is an IC2 sub-unit item; nine piles craft into one full Uranium-235.
Guide
Install Industrial Craft 2 and build a Macerator, Ore Washing Plant, and Thermal Centrifuge powered with EU; this chain is required to extract Tiny Pile of Uranium-235 from raw uranium ore.
Macerate Uranium Ore into Crushed Uranium Ore, wash it in the Ore Washing Plant to get Purified Crushed Uranium Ore, then run it through the Thermal Centrifuge to receive Tiny Pile of Uranium-235 plus Uranium-238 byproducts.
Repeat the centrifuge step until you have nine Tiny Piles of Uranium-235; U-235 is the rarer isotope, so expect to process many ore stacks.
Place nine Tiny Piles in a 3x3 crafting grid to craft one full Uranium-235 (id 2076), which is used in advanced IC2 nuclear recipes.
If you need fractional amounts for a recipe, place one full Uranium-235 in a 1x1 crafting slot to uncraft it back into nine Tiny Piles.
Nine Tiny Piles of Uranium-235 placed in a 3x3 crafting grid produce one full Uranium-235 (id 2076) in Industrial Craft 2.
Process Purified Crushed Uranium Ore in an IC2 Thermal Centrifuge; it outputs Tiny Pile of Uranium-235 along with Uranium-238 byproducts.
Yes. Placing one full Uranium-235 in a 1x1 crafting slot uncrafts it back into nine Tiny Piles of Uranium-235.
No. Tiny Pile of Uranium-235 is added by the Industrial Craft 2 mod and is not present in vanilla Java Edition or Bedrock Edition.
The Thermal Centrifuge separates uranium isotopes and outputs U-235 much less frequently than Uranium-238, mirroring real-world isotope abundance.