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| Fig. 1: Typical fission product yield by element. Source: Wikimedia Commons |
Nuclear fission has long been thought of as a solution to mitigate and even prevent global warming. It is true that nuclear fission does not contribute directly to CO2 emissions and global warming, however fission is not without environmental hazards. [1] One issue with nuclear fission is managing nuclear waste (spent fuel), which is primarily comprised of unused uranium, plutonium and other radioactive byproducts of the fission process. Managing nuclear waste has been a huge challenge for both government agencies as well as public utilities. Within the United States, cost estimates for the government failing to act to develop long term storage are estimated as high as $56 billion. [2] In addition to the ballooning costs of storage, there are also health hazards from radiation and global security issues due to the dangers of nuclear proliferation (mainly with regard to plutonium). To add to the complexity, spent fuel is highly radioactive and many of the species present in spent fuel can take in excess of tens of thousands of years to naturally decay to benign products. [3] As a result, spent fuel must be processed and made benign for the environment.
Spent fuel from nuclear reactors utilizing 235U (a typical fuel in reactors in the United States and Europe) contain a spectrum of isotopes created from the fission process. Part of these isotopes can be used in medical applications and industrial facilities, however the majority is hazardous, and requires tens of thousands of years to decay. [1] The remaining components of spent fuel are typically unreacted 235U, 238U and a mixture of plutonium (239Pu / 240Pu). [1] The plutonium is the primary concern with regards to nuclear proliferation.
Most fission results in two atomic species (ternary fission can also occur however is less likely), typically with mass numbers (number of protons & neutrons) centered around 90 to 100 AMU and 130 to 140 AMU. [4] This can be seen in Fig. 1 which represents the fission product yield for a typical fission event.
The species that are produced from 235U fission tend to be radioactive with long half-life periods (e.g. 137Cs half-life 30 years or 90Sr half-life 28 years and they emit strong gamma and beta radiation respectively).
Presently, there is no aggregate storage for the spent fuel for the United States. Most spent fuel resides in temporary storage facilities located onsite of nuclear power plants. [2] This is a liability for the United States. [5]
The use of nuclear energy can play a significant role in mitigating the impact of global warming. However before it can be used on a larger scale, a better plan should be established on how to manage spent fuel / radioactive waste.
© Eli Goldstein. 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.
[1] W. Tucker, "There Is No Such Thing as Nuclear Waste," Wall Street Journal, 13 Mar 09.
[2] J. Ahearne et al., "Consolidated Interim Storage of Commercial Spent Nuclear Fuel: A Technical and Programmatic Assessment", American Physics Society Panel on Public Affairs, February 2007.
[3] G. Audi et al, "The NUBASE Evaluation of Nuclear and Decay Properties", Nucl. Phys. A 729, 3 (2003).
[4] A. Newton, "The Fission of Thorium with Alpha-Particles," Phys. Rev. 75, 17 (1949).
[5] M. Bunn, "The Risk of Nuclear Terrorism - and Next Steps to Reduce the Danger," Testimony to the Committee on Homeland Security and Governmental Affairs, United States Senate, 2 Apr 08.
