|Fig. 1: Decommissioned Rancho Seco Nuclear Generating Station (Source: Wikimedia Commons)|
The US is currently in the process of shutting down several of its nuclear reactors. This process, known as decommissioning, is both complicated and expensive. The report will evaluate the current and past status of the US in retiring its reactors as well as the long-term implications and complications around the process.
Approximately 100 active nuclear reactors remain in the United States.  About 75% of reactors have been relicensed by the Nuclear Regulatory Committee for 20 additional years.  Yet these plants will have to be shut down at some point.  Already, over two dozen nuclear power plants have been decommissioned.  When a nuclear reactor is ready to be shut down, decommissioning can occur in a few different ways. 
Generally speaking, all nuclear plant decommissioning involves retiring the facility, decontaminating everything there, and removing contaminated materials such as fuels, coolants, and radioactive wastes.  Decommissioning often includes sealing the reactor vent to prevent any leakage of radioactive materials.  When decommissioning a reactor, waste must be properly dealt with and monitored: on average, there are 240 pounds of dangerous radioactive waste when a reactor is retired.  After all these processes, the land becomes available for other usage.  The end goal in decommissioning is reaching Greenfield Status: meaning the site is in the same condition as it was before the nuclear plant. 
DECON, SAFSTOR, and ENTOMB are three different methods for decommissioning plants.  DECON involves immediately removing and taking apart all equipment.  SAFSTOR involves delaying removal and breakdown, and monitoring the plant until it reaches safer radiation levels for decommissioning.  ENTOMB involves encasing radioactive materials on site with something such as concrete until safer radiation levels are reached.  ENTOMB is a less effective decommissioning process for non-research nuclear reactors, given the large amounts of resources needed and big half-lives of radioactive materials involved.  Hence, it is not normally used with most nuclear reactors.  Of the 14 reactors scheduled to be shut down in the near future, 6 will be decommissioned using DECON and 8 using SAFSTOR.  Both processes have pros and cons, and much of the decision around which process to use depends on the specific reactor. 
The Federal Government requires that nuclear plant decommissioning to take no more than 60 years.  Part of this mandate requires that all used fuel and other contaminated materials are removed from the site.  However, the government has not provided a space for this fuel to be taken: as a result, many of these plants do not get fully decommissioned, as spent fuel remains left behind.  Big Rock Point, Fort St. Vrain, Haddam Neck, Maine Yankee, Rancho Seco (see Fig. 1), Trojan, and Yankee Rowe are all reactors that have been nearly fully decommissioned, yet not quite, as used fuel remains. 
As the US retires many of its nuclear reactors, it continues to closely follow standards and safety protocols.  While the processes are expensive and long, properly carrying out the above methods is essential to ensuring the safety of residents near these plants.
© Danny Goldman. 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. Lochbaum "Life After Nuclear: Decommissioning Power Reactors," Bull. Atom. Sci. 70, 26 (2014).
 J. Keller, "Decommissioning Nuclear Reactors in the United States," Physics 241, Stanford University, Winter 2016.