|Fig. 1: The following chart shows the Nuclear wastes classifications.  (Source: Wikimedia Commons)|
Nuclear reactors produce roughly about 20% of the electricity in the United States. There are over 400 power reactors in the world (about 100 of these are in the USA). They produce base-load electricity 24/7 without emitting pollutants (including CO2) into the atmosphere.  They do, however, create radioactive nuclear waste which must be stored carefully. Nuclear waste can often be divided amongst the following categories: Low Level Waste (LLW), Intermediate Level Waste (ILW) and High Level Waste (HLW).  There are other forms of waste, that are typically referred to as Exempt Waste, but we often dont worry about them due to their minor impact on the environment. Therefore, our main focuses are Low Level Waste (LLW), Intermediate Level Waste (ILW), and High Level Waste (HLW), which must be all carefully managed.
Nuclear waste is considered to be the material that's formed after the nuclear fuel exists the reactor. The nuclear waste looks similar to the initial fuel that was placed inside the reactor, but due to the nuclear reactions that have occurred, the contents aren't quite the same. The key component of nuclear waste is the leftover smaller atoms, known as fission products.
LILW is considered to be the least radioactive waste of all. LILW is produced by "contamination of various materials with the radionuclides generated by fission and activation in the reactor core or released from the fuel or cladding surfaces."  LILW could refer to anything that comes in contact with radioactivity and becomes contaminated, these Volume reduction is particularly attractive for low-level waste which is generally of high volume but low radiation activity.  Significant improvements can be made through administrative measures, e.g. replacement of paper towels by hot air driers, introduction of reusable long-lasting protective clothing, etc., and through general improvements of operational implementation or "housekeeping".  Fig. 1 above is a graph that helps decipher between the different categories.
High level waste are the most radioactive waste of them all. High Level waste typically refers to (i) spent nuclear fuel from commercial and research nuclear reactors; (ii) liquid waste produced during the reprocessing of commercial spent nuclear fuel; (iii) waste generated by the nuclear weapons and naval propulsion programs.  High Level Waste show to increase significantly in temperature.  Due to their highly radioactive fission products, high-level waste and spent fuel must be handled and stored with care.  Since the only way radioactive waste can become harmless is through decay, its important to dispose them in way that ensures protection to the public for a long duration of time.
© Trevor Speights. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 D. Bodansky, Nuclear Energy: Principles, Practices and Prospects, 2nd Ed. (Springer, 2008).
 P. D. Riley, Nuclear Waste: Law, Policy and Pragmatism, 1st Ed. (Ashgate Publications Ltd, 2004).
 C. Dsouza, "Nuclear Waste Management," Physics 241, Stanford University, Winter 2012.
 V. M. Efremenkov, "Radioactive Waste Management at Nuclear Power Plants," IAEA Bull 31, No. 4, 37 April (1989).
 R. C. Ewing, W. J. Weber, and F. W. Clinard, "Radiation Effects in Nuclear Waste Forms for High-Level Radioactive Waste," Prog. Nucl. Energy 29, 63 (1995).
 "Classification of Radioactive Waste," International Atomic Energy Agency, General Safety Guide No. GSG-1, 2009.