Cesium-137, in the real-world, is a radioactive form of Cesium that is formed as fission byproducts of Uranium-235 and other fissile isotopes. For more information on the real world Cesium-137, see the Wikipedia article. For info on the Minecraft version of Cesium-137, keep reading!
In Minecraft, Small Piles of Cesium-137, Cesium-137 and other Cesium fuels are radioactive. A HAZMAT Suit must be worn when handling to prevent radiation poisoning.
A Small pile of Cesium-137 is obtained by placing Depleted Coaxium Fuel Rods in a Thermal Centrifuge.
Tiny Piles of Cesium can only be crafted into Cesium-137, a more usable form of this element.
Take 9 of these piles and craft them into the most powerful weapon fuel in this mod! That's right! for only 27 small piles, you could be the owner of some Cesium-137 Enriched nuclear fuel!