I have already touched on radioactive waste in several earlier posts but I wanted to treat the subject in a more systematic and thorough way. I am going to start with a breakdown of radioactive wastes into six categories.
Spent nuclear waste from nuclear reactors: Most of the fuel for nuclear reactors is in the form of ceramic pellets of uranium oxide which are packed into long metal rods. A few thousand of these rods are joined together into what is called a “fuel assembly.” When the fuel in the assembly is exhausted and can no long power the reactor, the assembly is removed. Because there is no permanent storage or disposal solution for spent nuclear fuel, the spent fuel assemblies are usually stored in pools of water which dissipates heat from the assembly and blocks the radiation emitted by the rods.
High-level waste from spent fuel reprocessing: Some spent fuel is dissolved in corrosive chemicals and then unfissioned uranium and plutonium are recovered from the resulting liquid. Ninety nine percent of the waste from reprocessing is generated by defense related nuclear weapons research and development. There are plans to solidify this waste but for the time being the waste is stored in liquid form in underground steel tanks in facilities in Idaho, Washington, South Carolina and New York.
Transuranic Radioactive Waste: Transuranic elements are man-made elements that lie above uranium in the periodic table. Transuranic wastes are mainly generated by the production of nuclear weapons. Plutonium is the most prominent transuranic in such wastes. Also included in this category are contaminated clothes, tools, lab equipment, and containers.
Uranium mill tailings: When uranium is mined and milled, huge piles of waste are generated which generally remain in the area of the mill. Radium is the most important radioactive material in the mill tailings. It decays into radioactive radon gas which diffuses into the atmosphere. Mill tailings also include selenium, molybdenum, uranium and thorium.
Low-level radioactive waste: Low-level radioactive waste includes contaminated industrial or research waste. This includes clothing, packaging materials, organic fluids, and other waste products that do not fall into the other categories in this list. This waste is generated by DOE research facilities, private industry, nuclear plants, universities and other institutions.
Naturally occurring and accelerator produced radioactive waste: There are naturally occurring radioactive materials that can be concentrated by human activity and pose a hazard. More diffuse naturally occurring wastes come from multiple sources including metal mining and processing waste, coal ash, phosphate waste, oil and gas production waste and water treatment residue and soil removed from above a deposit of uranium ore. Particle accelerators use magnetic fields to accelerate nuclear particles to high velocities for research, medical and industrial purposes. Short lived radioactive waste can be produced by such accelerators.
In future posts, I will go into more detail on each of these types of waste including the problems and dangers they pose and methods of storage and disposal.
Ionizing radiation warning symbol created in 2007 by the International Atomic Energy Agency and the International Organization for Standardization:
