Nuclear waste consists either of fission products formed from atom splitting of uranium, cesium, strontium, or krypton or from transuranic elements formed when uranium atoms absorb free neutrons. Wastes from transuranic elements are less radioactive than fission products; however, these elements remain radioactive far longer than fission products. Transuranic wastes include irradiated fuel (spent fuel) in the form of twelve-foot- (four-meter-) long rods, high-level radioactive waste in the form of liquid or sludge, and low-level waste (nontransuranic or legally high-level) in the form of reactor hardware, piping, toxic resins, water from fuel pools, and other items that have become contaminated with radioactivity.