Nuclear-waste management is a multi-billion dollar problem, and the future of nuclear power will depend on its resolution. Four scenarios depict possible outcomes and impacts on the electric power industry.
Nuclear-waste management is a multi-billion dollar problem wrapped in a complex web of politics, public opinion and technology choices. Embracing a greater future role for nuclear energy requires, in part, resolving the perennially deferred problem of managing and ultimately disposing of the high-level waste (HLW) from this nation’s current and proposed nuclear power reactors.
Yucca Mountain, the Nevada site studied for over 30 years, was identified during the Reagan administration as the intended permanent repository for the disposal of United States HLW from nuclear reactors. However, various entities, including the state of Nevada, have sued the federal government with hopes of preventing the Yucca Mountain waste repository from ever opening, and other states have shown reluctance to allow transit of the nuclear waste, especially near populated centers.
More than $9 billion later, the debate over Yucca Mountain as a waste repository is at a stalemate. Despite DOE’s recent license application to the Nuclear Regulatotry Commision, the site is at least eight years from receiving the first shipment of spent nuclear fuel. Meanwhile, many of the storage pools located at nuclear plants throughout the country are nearing capacity, increasingly requiring the spent fuel to be stored in dry casks. The Bush administration appears to want to reverse the 30-year policy of storing nuclear waste, by instead encouraging new design of power plants that can reprocess the spent fuel.
The management of nuclear waste from power plants includes consideration of both costs and risks of supplying electricity from nuclear energy. In this larger context, scenario analysis is used to identify the role that nuclear energy may play under alternative conditions. These scenarios are time-based views of plausible futures that help planners and decision makers share a common understanding of the component pieces that may impact their decisions. Like traveling down a road, the scenario may contain signs that aid in making decisions at a later time and off-ramps or opportunities prompting decisions to take another turn. When applied to nuclear-waste management, scenario analysis can provide a common framework for discussion and yield better decisions.
Nuclear fuel begins as raw mined uranium ore with a low concentration of the desired uranium 235. Mining and enrichment constitute the front-end of the fuel cycle. For the operational phase of the fuel cycle, enriched fuel typically will remain in the reactor and produce electricity for three to five years. Storage, ultimate transport and disposal constitute the back-end of the fuel cycle. Fuel cycles can be open or closed. In an open cycle, also called once-through, enriched fuel is used once within the reactor to produce power until it is spent. It is then placed into a cooling pool for storage. Regarded as short-term storage, the spent fuel will reside as little as one, but mostly likely five-to-ten years, in the cooling pool, losing a significant portion of its radioactivity and thermal energy. At this point, the fuel may be placed into dry-cask storage. Each dry cask contains approximately 10 tons 1 of HLW in a cement and steel structure on-site at the nuclear plant. Spent fuel usually is transferred to dry casks after cooling for five-to-ten years in storage pools. Considered a stable and safe option, it is believed that the HLW can remain in dry-cask storage for 50 or more years.
In a closed cycle, spent fuel similarly follows the front-end and operational steps, including pool storage. However, at this point, the spent fuel may be reprocessed to recover primarily the plutonium. This has the attraction of providing greater use of the raw uranium by cycling the fuel and yielding much lower amounts of HLW than does the once-through cycle. Disadvantages include the creation of plutonium that, if stolen, could be used to develop nuclear weapons. Another disadvantage is the additional capital and operating costs associated with reprocessing. If a nuclear fleet isn’t designed with reprocessing in mind, then significant investment is required to recapture the plutonium.
For both open and closed fuel cycles there is a need to permanently dispose of various forms of nuclear waste. There is wide agreement that permanent waste disposal facilities should be sited in highly stable, deep geologic structures. Permanent disposal of nuclear waste is set to a high bar: No nuclear waste may leach into the surrounding biosphere for 10,000 or more years. It also requires transport infrastructure, containment facilities and insulating materials to backfill after burying the waste.
Different countries have focused on alternative types of nuclear-fuel cycles. Principally, these reflect differing views on the perceived advantages of reprocessing nuclear fuel versus relying on mined and enriched nuclear fuel for power generation. The future availability of nuclear fuel doesn’t seem in doubt; however, nuclear fuel prices have risen and appear to be more volatile.
The United States has not allowed reprocessing of nuclear fuel since the mid-1970s due to concern over weapons proliferation from plutonium produced during nuclear reprocessing. This prompted the U.S. nuclear fleet to accumulate HLW by utilizing the once-through fuel cycle for the last 30 years. In the absence of a Yucca Mountain-like permanent disposal facility, most of this nation’s spent fuel is resting in cooling pools, often 40 or more feet deep, located at the nuclear plant sites. As spent fuel fills the cooling pools over time, operators have moved an increasing quantity of spent fuel to dry-storage casks. Scattered throughout the nation are about 56,000 total metric tons of HLW with about 2,000 additional metric tons created per year.
At this rate, the United States easily will exceed the original legislated HLW total allowed storage capacity of 70,000 metric tons at Yucca Mountain years before the 2017 cut-off date; however, the current 70,000 metric-ton limit does not reflect a permanent physical limitation. In 2007, the DOE advocated doubling the allowed capacity of Yucca Mountain, while others have suggested the physical limit at Yucca should be set at 250,000 metric tons or more. Once opened, the planned rate of disposal into Yucca Mountain is 3,000 metric tons per year, 2 implying a drawdown of accumulated storage capacity that will take decades. The DOE, as part of the 1987 amended Nuclear Waste Policy Act, is required to identify a second permanent disposal site prior to 2010. Candidate sites in a number of states have been identified, but with a presumed 25-year development period, a second site would be available no sooner than 2035.
In the meantime, utilization of on-site dry casks as an interim solution apparently will increase, as the creation of one or more government-sponsored interim facilities appears unlikely. The national cost of storing spent fuel in dry casks is estimated at $300 million to $500 million per year. The federal government likely will continue to pay the bill for this dry-cask storage because of a pact with utilities that the government has not fulfilled: The government was to “take title” of HLW by 1998.
The Bush administration has encouraged reprocessing as part of the 2006 Global Nuclear Energy Partnership (GNEP). The stated objectives of GNEP include furthering national security, transitioning the United States from an open-cycle to closed-cycle nuclear industry in order to exploit theoretical Generation IV nuclear-systems technology, provide fuel and technology to developing countries and to aid in nuclear-waste disposal. In spite of a current membership of 19 countries, GNEP has been controversial. On economic grounds, the Congressional Budget Office determined that this reprocessing path would be much more costly than waste disposal. On a national security basis, the Union of Concerned Scientists and others have implored Congress to reject the program because it would proliferate plutonium. Finally, from a nuclear-waste management standpoint, the technologies envisioned, while producing a lower volume of HLW, still requires eventual disposal in a Yucca-like repository. Meanwhile, the movement towards reprocessing is meeting firm opposition, including a 2008 GNEP budget set at one-half requested levels and with no support for demonstration projects.
Outside of the United States, countries including the U.K., France and most recently Japan, reprocess spent nuclear fuel in a closed cycle as an integral part of their nuclear programs. As a consequence, these countries have created far less HLW per unit of electricity produced, yet they have developed a large amount of very high level waste in the form of plutonium. In this processed form, plutonium is far less toxic and is more easily used to create a fission reaction; thus it is more prone to theft and more desirable to steal than if left in the post-reactor spent state. This has contributed to general concerns over proliferation of weapons-grade nuclear materials and more specifically over rogue nations or terrorists acquiring these materials to build a nuclear bomb.
Nuclear-waste management problems are not unique to the United States. To date, no country in the world has begun to store its spent fuel in permanent repositories. The world has accumulated about 250,000 metric tons of highly radioactive waste. The Nuclear Energy Agency (NEA) and others have encouraged cooperation among nations to minimize the proliferation of weapons-grade materials and to consider regional solutions to waste repositories. Indeed, a pillar of the 1968 Non-proliferation Treaty is the tenet that all countries, following other pillars of non-proliferation and disarmament, have the right to pursue nuclear energy.
The concept of international cooperation has extended to nuclear-waste management as well. The International Atomic Energy Agency (IAEA) has discussed combining both regional and country-specific nuclear-waste repositories, utilizing the safest geologic structures available. While a number of countries ultimately will use their own repositories, the approach especially has appeal for countries with smaller nuclear programs and that lack the correct geology for repository siting. The Massachusetts Institute of Technology (MIT) and others have proposed the use of deep boreholes, thousands of meters inside the earth’s mantle, as a possible future disposal technology. 3 The geology needed to support this approach is found in many places around the world. The benefits of this method include a very stable resting place well below the water table and possibly the ability to rely on the waste’s thermal energy to create a melt zone that eventually cools and further encapsulates the nuclear waste inside solid rock.
The role of nuclear power hinges on the same fundamental elements as in the past: public opinion, relative power economics, and safety concerns stemming from both nuclear proliferation and nuclear-waste disposal. Utilizing a scenario-based approach permits testing the ranges of possible future outcomes and their impacts on the electric utility industry. Within each scenario we can create consistent assumptions for the future that integrate issues relating to the impacts of nuclear power, emissions, other technologies and larger world trends.
The assumptions for each established scenario can help to define the role of future nuclear additions and their relative economics. From this, simulation models are used to measure the amount of nuclear generation, the displacement of CO2 and other emissions and subsequent nuclear waste created in each scenario. 4 All scenarios share common once-through nuclear technology, based on the significant economic advantage from avoiding reprocessing costs and the relatively low cost of mining and enrichment of nuclear fuel. Further, all existing nuclear plants are assumed to extend their operating permits to achieve a sixty-year life. Yucca Mountain is presumed to open, but is delayed until 2023. All scenarios are evaluated from 2008 to 2050.
• Global Turmoil: Terrorist attacks constrain gas and oil imports. Gazprom disruptions in gas supply leads to global stagnation, and a U.S. recession, which is followed by sustained low economic growth. Reducing dependence on Middle East oil and LNG imports becomes critical. The U.S. develops a “protectionist” view due to import restrictions, and struggles to become self-reliant. Marked by little competition or retirement of generation capacity, extended recovery from overbuild, and utilities’ gains vis-à-vis IPPs in a business environment where competition takes a backseat to energy independence. Nuclear implication: The Global Turmoil scenario reflects a constrained nuclear world due to unavailability of supply resources. Only 7 GW of new nuclear resources are added to the generation mix by 2030 and 42 GW by 2050. In this scenario, nuclear generation begins to decline to below the historical levels of 20 percent of national energy. In addition, new resources do not enter service until 2021.
• Technology Evolution: Undeniable evidence of global warming leads to election of “green candidate,” enactment of phased-in greenhouse gas constraints, and a big push for renewable energy and energy efficiency. Less efficient and highly polluting plants are replaced by IGCC, CO2 sequestration technology, and other new low-GHG technologies. Nuclear implication: A second generation nuclear capacity fleet is built to fill the gap. Technology Evolution spurs growth of nuclear construction. Construction schedules are accelerated with building beginning in 2015. Advances in technology provide more modularization and construction costs fall to the low end of the spectrum. Sixty gigawatts of new nuclear resources are added to the generation mix by 2030 and 313 GW by 2050. The 313 GW also reflects replacement of the existing nuclear fleet with new nuclear resources.
• Global Economy: The shift of industrial U.S. load to the service industries and a policy of global consolidation drives the U.S. to forge a pact with European countries to stabilize global economic inflationary pressures. The pact also leads to pooling of energy resources to stabilize the fuel imports, as well as economies for consolidation of energy infrastructure. In addition, the United States benefits from the development of a global cap-and-trade program for CO2. Nuclear implication: In the Global Economy scenario, 60 GW of nuclear resources are added by 2030 and 234 GW by 2050. Approximately 75 percent of the existing nuclear fleet is replaced with new nuclear resources. The ability to share resources internationally stimulates the manufacture of nuclear components needed for construction. In addition, the operation of resources is globalized to facilitate more efficient operations of both existing and new resources.
• Return to Reliability: Growing concern over electricity reliability due to brownouts and increased outages drives a lack in consumer confidence. The Electric Reliability Organization (ERO) recognizes the shortfall of the aging transmission infrastructure and leads to further consolidation of planning areas. To address concerns, reliability protocols are created increasing reserve margins for regions. Federal incentives are put in place for utilities and RTOs to build additional transmission lines to meet demand. Nuclear implication: In the Return to Reliability scenario, 39 GW of nuclear resources enter service by 2030 and 116 GW by 2050, replacing 50 percent of the existing nuclear fleet with new nuclear resources. Generally, these units are built at existing sites where multiple units previously had been planned; therefore, there may already be on-site storage for HLW.
The four scenarios illustrate a range of outcomes associated with significantly different, plausible futures. These futures will create different levels of demand for power and consequently total generating capacity (see Figure 1). These resource mixes imply alternative total green-house gas emissions (see Figure 2).
Each scenario contains a level of HLW created as a result of greater or lesser reliance on nuclear technology, consistent with that scenario. Note that the Technology Evolution case reaches an upper range of around 225,000 tons of HLW by 2050; while the Global Turmoil case with much lower use of nuclear generation, creates about 125,000 tons of HLW over the same time period (see Figure 3). This translates to an upper bound of over three-Yucca Mountains equivalents and a little less than two Yucca Mountain equivalents in the Global Turmoil case at the currently legislated capacity of 70,000 metric tons.
A further evaluation of the Technology Evolution case illustrates plausible transitions of HLW from cooling pool to dry cask to permanent repository. If interim-storage facilities were developed, they presumably would displace some portion of the on-site dry cask shown in the graph. Due to the currently established disposal rate at Yucca Mountain, the 70,000 metric ton limit will be reached around 2046. In fact, because the disposal rate is the binding constraint in this analysis, the same conclusion holds in all scenarios: There is not enough current capacity at Yucca Mountain. However, if it opened for disposal, there would be sufficient capacity at Yucca Mountain to last almost to mid-century.
Thus, a de facto robust strategy emerges across the four scenarios. The United States can maximize its use of cooling pools and dry casks with minimal safety impacts, while moving forward with Yucca Mountain as a permanent repository. This decades-long timeframe permits greater opportunity for off-ramps from this strategy. Options include extending the original Yucca Mountain capacity beyond 70,000 metric tons, international consolidation of nuclear waste, establishment of an alternative disposal technology such as deep borehole and technology breakthroughs achieved by one or more renewable technologies.
1. von Hippel, Frank, “Rethinking Nuclear Fuel Recycling,” Scientific American, New York, May 2008.
2. Rogers, Kenneth A., et al, “On-site Storage,” Calculated Risks: Highly Radioactive Waste and Homeland Security, Ashgate Publishing, Burlington, 2007.
3. MIT Nuclear Study Committee, The Future of Nuclear Power, An Interdisciplinary MIT Study, Massachusetts Institute of Technology, Cambridge, 2003.
4. Strategy Advisors, “Detailed Look at the Four Global Energy Horizon Scenarios,” Scenarios of the Global Energy Future, Ventyx, Columbus, 2007.