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| Fig. 1: Process for managing commercial spent nuclear fuel. [1] (Courtesy of the GAO) |
Today, there are approximately 86,000 tons of spent nuclear fuel in the US; this volume grows by around 2,000 tons per year. [1]
While relatively small in volume, this waste needs to be stored indefinitely, as components of it namely, the 3-4% of volume that is fission products and minor actinides [2] are highly radioactive and harmful to human health on the timescale of 10,000 years. [1] If nuclear waste is released into the environment during this decay period, it can contaminate large areas of land for generations. [3] Long-term, secure storage is therefore important.
The fuel cycle is shown in Fig. 1. When used fuel is removed from a reactor, it is extremely radioactive and produces a large amount of decay heat. Before permanent storage, it must therefore be cooled, or risk damage to the storage container. To do this, spent fuel is placed into pools of water (fuel pools) at the reactor site for at least 5 years, per industry practice. [1]
After this cooling period, the waste can be stored permanently. There is consensus that, due to its longevity, nuclear waste should be stored deep underground in geologic repositories, where it can be kept undisturbed and accidental or deliberate release can be prevented. [4]
At present, the US has no permanent solution on the table for the storage of nuclear waste.
The Nuclear Waste Policy Act of 1982 (NWPA) requires the Department of Energy (DOE) to dispose of nuclear waste in a geologic repository, with the latest amendment specifying the site of Yucca Mountain, Nevada. [5] However, the DOE terminated its activities at Yucca Mountain in 2010 after significant political backlash resulted in Congress pulling funding for the site.
As such, spent fuel is stored on-site at 75 nuclear power plants (both operational and shut down), even after the cooling period. On many sites, it is transferred from the spent fuel pools to dry casks (concrete containers) to make room for newly generated spent fuel. [1] Per the latest numbers made public in 2014, 63 of these sites were storing spent fuel in dry casks. [6] The Nuclear Regulatory Commission (NRC) believes that dry casks are a reasonable interim solution but note that storage durations of 100+ years create the risk of container degradation and so would require ongoing monitoring this is an issue, since the time horizon of the waste far exceeds the agency's likely existence. [6]
Estimates of the cost of nuclear waste management vary. TRW Environmental Safety Systems Inc. estimated the construction cost of waste storage facilities at reactor sites at $14M per site, with annual monitoring costs of $1M while the reactor was operational and $5.6M - $12.7M after shutdown. These figures are not dependent on the amount of fuel stored. [7]
The U.S. Government Accountability Office projected the 100-year Net Present Value (NPV, i.e., the 100-year cost discounted by the cost of funds) for interim storage at $109,341 to $211,393 per MTHM (Metric Tons of Heavy Metal) for centralized storage and $94,762 to $318,651 per MTHM for reactor-site storage. [8]
This would imply that 100 years of interim storage for existing spent fuel in the US would cost $8-27 billion, with an additional liability of $200-600M created each year.
International cost estimates for permanent nuclear waste disposal range from $148,000 to $1,041,000 per MTHM, depending on the type of host rock for repositories. It is challenging to compare these studies, however, as assumptions and methodologies vary significantly. [6]
Even within a single project, costs can vary. The Government Accountability Office's analysis of Yucca Mountain projected a total NPV (i.e., lifetime cost discounted by the cost of funds) that Barron and Hill translated into a per unit cost of $298,866 to $488,391 per MTHM for repository disposal, assuming all current reactors operate for 60 years. [9] They added an additional $109,341 per MTHM in sunk costs. [6]
That would imply a total cost of $26-42 billion for existing waste, plus $9-10 billion in sunk costs: $35-52 billion. Again, this would grow by $0.6-1.0 billion per year as new waste was generated. This calculated figure is in line with the DOE's estimate of $50.2 billion in (unfunded) liabilities, per their 2023 Agency Financial Report. [10]
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| Fig. 2: NPV of nuclear waste management costs. (Source: C. Cranmer, after Barron and Hill. [6]) |
This sounds high and it is, in absolute terms but to understand the relative cost vs. the cost of electricity, we need to translate to a cost per kWh. Barron and Hill did this in 2019. [6] Their study considered three different cost scenarios, as well as two different methods of discounting these costs. As seen in Fig. 2, they found that the cost of long-term storage ranged from < $0.001/kWh to around $0.013/kWh, with the mid-cost scenario suggesting costs of $0.0025-0.006/kWh. The cost scenario and the way in which the cost was discounted had a significant impact. This is in line with prior IAEA estimates of $0.0008-0.01/kWh. [6]
Put into context, the cost of power from a nuclear power plant with an open fuel cycle ranges from $0.38/kWh to $0.71/kWh, depending mainly on plant age and type. [11] For old reactors, long term fuel disposal liabilities could therefore be a significant portion of levelized costs (7-20%), while for new reactors this share is lower (3-10%).
This cost was originally funded by a charge of $0.0001 per kilowatt-hour of electricity produced, collected from utilities by the DOE and placed into a Nuclear Waste Fund. However, following litigation in 2014, no new fees have been collected utilities alleged that the federal government had no viable plan for a long-term repository and therefore should not be charging fees to the utilities. [1]
In conclusion, the management and disposal of spent nuclear fuel in the US presents significant financial and logistical challenges. Reprocessing of spent fuel could significantly reduce its volume; however, it is not currently a viable pathway due to legislation from 1977 mandating a once-through fuel cycle.
As the volume of nuclear waste continues to grow, the time-sensitivity of this challenge will increase. We must find a balanced approach that considers technological feasibility, political appetite, and economic impact.
© Caitlin Cranmer. 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.
[1] "Commercial Spent Nuclear Fuel: Congressional Action Needed to Break Impasse and Develop a Permanent Disposal Solution," U.S. Government Accountability Office, GAO-21-603, September 2021.
[2] O. H.Zabunoǧlu and L. Özdemir, "Purex Co-Processing of Spent LWR Fuels: Flow Sheet," Ann. Nucl. Energy 32, 151 (2005).
[3] M. D. Bondarkov et al., "Environmental Radiation Monitoring in the Chernobyl Exclusion Zone - History and Results 25 Years After," Health Phys. 101, 442 (2011).
[4] Disposal of Radioactive Waste on Land; Report (National Academies Press, 1957).
[5] "Nuclear Waste Policy Act, as Amended, with Appropriations Acts Appended," U.S. Department of Energy, March 2024..
[6] "Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel," US Nuclear Regulatory Commission, NUREG-2157 Volume 1, September 2014.
[7] "Total System Performance Assessment 1995: An Evaluation of the Potential Yucca Mountain Repository," TRW, November 1995.
[8] R. W. Barron and M. C. Hill, "A Wedge or a Weight? Critically Examining Nuclear Power's Viability as a Low Carbon Energy Source From an Intergenerational Perspective," Energy Res. Soc. Sci. 50, 7 (2019).
[9] "Nuclear Waste Management: Key Attributes, Challenges, and Costs for the Yucca Mountain Repository and Two Potential Alternatives," U.S. Government Accountability Office, GAO-10-48, November 2009.
[10] "Agency Financial Report - Fiscal Year 2023," U.S. Department of Energy, DOE/CF-0201, 2023.
[11] R. Gao et al., "The Economic competitiveness of Promising Nuclear Energy System: A Closer Look at the Input Uncertainties in LCOE Analysis," International Journal of Energy Research 43, 3928 (2019).