Nuclear power generation is well established, but efforts worldwide to develop permanent disposal sites for highly radioactive waste remain nascent at best. If this were a horse race, you’d have to say the smaller horses are winning.
The U.S. Department of Energy (DOE) published in early January its “Strategy for the Management and Disposal of Used Nuclear Fuel and High-Level Radioactive Waste,” an 18-page outline of how the Obama administration plans to implement recommendations made by its so-called Blue Ribbon Commission (BRC) on America’s Nuclear Future. The commission was set up in 2010 to review and recommend a plan of action to manage and dispose of used nuclear fuel and high-level radioactive waste.
With appropriate authorizations from Congress, the Energy Department said it hopes to implement a program over 10 years that:
- Sites, designs, licenses, constructs, and begins operations of a pilot interim storage facility by 2021 with an initial focus on accepting used nuclear fuel from shut-down reactor sites.
- Moves toward siting and licensing a larger interim storage facility to be available by 2025 that will have sufficient capacity for enough used nuclear fuel to reduce expected government liabilities.
- Makes demonstrable progress on the siting and characterization of repository sites to facilitate the availability of a geologic repository by 2048.
Other aspects of the administration’s proposal include requiring consent-based siting, reforming the funding approach, and establishing a new organization to implement the program.
This seemingly back-to-square-one action runs counter to the Nuclear Waste Policy Act of 1982 and subsequent congressional action that, in 1987, named Yucca Mountain in the Nevada desert as the sole candidate to receive U.S. domestic radioactive nuclear waste. Lawsuits are under way challenging the Obama administration’s decision to scrap development of a Yucca Mountain repository and establish a new process for designating and building a long-term waste storage facility.
Those decisions, which came early in Obama’s first term, were motivated in part by politics. As described in prior articles (see the sidebar “The Quest for Long-Term SNF Storage”), candidate sites in Texas and Washington State were dropped from consideration in favor of Yucca Mountain largely because Nevada’s congressional delegation couldn’t block action anointing Yucca Mountain. In the intervening years, Nevada Senator Harry Reid gained stature and as Senate majority leader found an ally to stop Yucca Mountain’s development once Barack Obama took office in 2009. As a result, some $15 billion in taxpayer investment at the Nevada site now seems likely to lead to nothing. What’s more, the timetable for establishing a national nuclear waste repository has been reset until at least 2048, according to the DOE’s January recommendation.
The Nuclear Energy Institute (NEI), an industry trade group, said it welcomed the Energy Department’s recommendation and said many of the concepts put forward by the BRC and recommended by the DOE have enjoyed support among its members and other experts.
“After two years of BRC deliberations and an additional year for DOE to develop its strategy, it is essential that the nuclear waste fee be used solely for its intended purpose—to cover the cost of used fuel management and disposal,” the NEI said. The fee (equal to one-tenth of a cent per kilowatt-hour of electricity) paid by consumers of electricity from nuclear power plants, totals about $750 million a year and is at present “effectively unavailable for its intended purpose,” the NEI said.
Conflict remains, however. In late January, the NEI joined state utility regulators in asking a federal court to reopen a lawsuit that challenged the DOE’s practice of continuing to collect fees from nuclear utilities to pay for long-term storage (see sidebar “Fee Dispute Re-ignites”). The federal government already faces a large and growing liability to pay claims resulting from its failure to begin accepting waste from commercial utilities under the 1987 Nuclear Waste Policies Act. According to a Congressional Research Service report, as of mid-2012 the government had paid around $1 billion to settle claims by utilities that the DOE had, at least in part, breached its contracts to accept spent nuclear fuel (SNF). These claims stem from some 76 contracts the DOE signed in the early 1980s, largely with commercial utilities, of which 74 have filed claims for damages arising from failure to accept the SNF by 1998.
SNF continues to pile up at a rate of around 2,000 metric tons a year, the congressional report said. To date, more than 67,000 metric tons of SNF in more than 174,000 assemblies currently are stored at 77 sites in 35 states. Of the nation’s 104 existing nuclear reactors, all have wet storage pools for SNF. These wet pools are required to allow a safe “cooling off” period of up to five years after fuel assemblies are removed from a reactor. The pools hold around three-quarters (49,338 out of 67,450 metric tons of uranium, or MTU) of the current commercial SNF inventory. The remaining one-quarter (equal to about 18,112 MTU) of commercial SNF is stored in dry casks on concrete pads or in vaults. As wet storage pools become filled using “dense packing” storage methods, dry storage increasingly is being used (Figure 1).
|1. Nuclear fuel cycle. The multi-step process from uranium mining to enrichment to use in a reactor is well known. Disposal, at the very end of the cycle, remains something of a black box. Source: Nuclear Regulatory Commission|
The U.S. is not alone in figuring out what to do with spent nuclear fuel. Worldwide, some 436 operational nuclear power reactors operate in 32 countries. There are another 122 permanently shut-down nuclear power reactors. To date, however, few permanent disposal solutions have been implemented. What’s more, the siting approach favored by the DOE—namely, voluntary cooperation on the part of a host community—suffered a setback in the UK earlier this year when local authorities there voted against a storage scheme, effectively killing a project that had been under development for years.
Classifying Radioactive Waste
Not all nuclear waste is the same, and disposal techniques range from tipping it at commercial landfills to long-term geologic storage with remote monitoring. As a starting point, consider that a typical 1,000-MWe light water reactor generates 200 to 350 cubic meters of low- and intermediate-level waste each year. That reactor also likely will discharge about 20 cubic meters (roughly 27 metric tons) of used fuel each year. In countries where used fuel is reprocessed, around 3 cubic meters of vitrified waste (in the form of glass) are produced. By comparison, an average 400,000 metric tons of ash are produced from a similarly sized coal-fired plant. An overview of the range of radioactive waste and disposal techniques follows, adapted from the World Nuclear Association (WNA).
Exempt waste and very low-level waste (VLLW) contain radioactive materials at a level considered not harmful to people or the environment. It consists mainly of material produced during rehabilitation or dismantling operations at nuclear industrial sites. Industries such as food processing, chemical, and steel production also produce VLLW, but waste typically is disposed of with “domestic” refuse. Countries including France are developing sites to store VLLW in specifically designed disposal facilities.
Low-level waste (LLW) is generated by hospitals and industry, as well as the nuclear fuel cycle, and contains small amounts of mostly short-lived radioactivity. It does not require shielding during handling and transport and is suitable for shallow land burial. To reduce its volume, it is often compacted or even incinerated before disposal and accounts for around 90% of the volume and 1% of the radioactivity of all radioactive waste worldwide.
Intermediate-level waste (ILW) contains higher amounts of radioactivity and some requires shielding. It typically comprises resins, chemical sludges, and metal fuel cladding, as well as contaminated materials from reactor decommissioning. Smaller items and most nonsolids may be solidified in concrete or bitumen for disposal. This type of waste makes up around 7% of the volume and has 4% of the radioactivity of all radioactive waste.
High-level waste (HLW) results from “burning” uranium fuel in a nuclear reactor. HLW contains fission products and transuranic elements (that is, elements having atomic numbers greater than uranium) generated in the reactor core. It is highly radioactive and “hot” (contaminated), and requires both cooling and shielding. Referred to as “ash” produced by “burning” uranium, this waste accounts for more than 95% of the total radioactivity produced in electricity generation. HLW has both long-lived and short-lived components, depending on how long it will take the radioactivity of particular radionuclides to fall to levels considered no longer hazardous for people and the environment.
Uranium oxide concentrate from mining, essentially the well-known “yellowcake,” is considered to be barely more radioactive than granite used in buildings. Through refinement and conversion to uranium hexafluoride gas, it undergoes enrichment to increase the U-235 content from less than 1% to about 3.5%. Following this step, it is turned into a hard ceramic oxide for assembly as reactor fuel elements.
The main byproduct of enrichment is depleted uranium, principally the U-238 isotope. About 1.2 million metric tons of depleted uranium are now stored. Some is used in applications where its high density makes it valuable, such as in the keels of sailing vessels and military projectiles. It is also used (with reprocessed plutonium) to make mixed oxide fuel (MOX) and to dilute highly enriched uranium from dismantled weapons for use as reactor fuel.
Waste from Electricity Generation
Highly radioactive fission products and transuranic elements are produced from uranium and plutonium during reactor operations and are contained within the used fuel. LLW and ILW are produced during power generation operations (such as cleaning reactor cooling systems), in fuel storage ponds, and during decontamination of equipment, filters, and metal components that have become radioactive in or near the reactor.
Storage is handled mostly using ponds at reactor sites or, occasionally, at a central site. If the used fuel is reprocessed—as it is for UK, French, Japanese, and German reactors—HLW comprises highly radioactive fission products and some transuranic elements with long-lived radioactivity. These are separated from the used fuel, enabling the uranium and plutonium to be recycled.
The HLW also generates heat and requires cooling. It is vitrified into borosilicate glass, encapsulated into stainless steel cylinders around 4.5 feet high, and stored for eventual disposal underground. France operates two commercial plants to vitrify HLW left over from reprocessing oxide fuel, and there are plants in the UK and Belgium. The capacity of these plants is around 2,500 canisters (about 1,000 metric tons) a year, and some have been operating for decades.
Used reactor fuel that is not reprocessed still contains all the highly radioactive isotopes, meaning the entire fuel assembly must be treated as HLW for direct disposal. However, because it consists largely of uranium (with some plutonium), it represents a potentially valuable resource. As a result, an increasing reluctance exists to dispose of it permanently. Current thinking is that after 40 to 50 years the heat and radioactivity have fallen to around one-thousandth the level at removal, providing a technical incentive to delay permanent storage and find some other use for it.
Recycling Used Fuel
Used fuel still contains some of the original U-235 as well as plutonium isotopes that have been formed inside the reactor core and U-238. These account for roughly 96% of the original uranium and more than half of the original energy content. Reprocessing, which is done in Europe and Russia, separates this uranium and plutonium from the wastes for reuse in a reactor. Plutonium that results from reprocessing is recycled through a MOX fabrication plant, where it is mixed with depleted uranium oxide to make fresh fuel. European reactors currently use more than 5 metric tons of plutonium a year in fresh MOX fuel.
Commercial reprocessing plants operate in France, the UK, and Russia with a capacity of some 5,000 metric tons a year. A new reprocessing plant with an 800 metric ton per year capacity is being constructed at Rokkasho in Japan. France and the UK also reprocess used fuel for utilities in other countries. For example, Japan has made more than 140 shipments of used fuel to Europe since 1979. Russia also reprocesses spent fuel from some Soviet-designed reactors in other countries.
Storage ponds at reactors, and those at centralized facilities such as in Sweden, are 20 to 40 feet deep to allow several feet of water to cover the used fuel, which is in the form of racked fuel assemblies 12 feet long and standing on end. These pools are made of reinforced concrete with steel liners and often are designed to hold all the used fuel for the life of a reactor.
Some storage of fuel assemblies that have been cooling in ponds for at least five years is continued in dry casks, or vaults with air circulation inside concrete shielding. One system involves sealed steel casks or multi-purpose canisters (MPCs), each holding about 80 fuel assemblies with inert gas. Casks/MPCs also may be used to transport and eventually to dispose of the used fuel. For storage, each is enclosed in a ventilated storage module made of concrete and steel. These commonly stand on the surface, are about 18 feet high, and are cooled by air convection. A collection of casks or modules constitute what’s known as an Independent Spent Fuel Storage Installation. In the U.S. they are licensed by the Nuclear Regulatory Commission separately from power plants and are intended for interim storage only. About one-quarter of U.S. used fuel is stored this way.
|Global spent nuclear fuel disposal strategies. Reprocessing is a favored strategy in many countries, but long-term geological storage remains years from reality for most nations with nuclear power. Source: World Nuclear Association|
To ensure that no significant environmental releases occur over tens of thousands of years, “multiple barrier” geological disposal is planned to immobilize radioactive elements in HLW and some ILW and isolate them from the biosphere. The main barriers to be built using this approach include:
- Immobilizing waste in a matrix such as borosilicate glass or synthetic rock.
- Sealing waste inside a corrosion-resistant container, such as stainless steel.
- Locating the container deep underground in a stable rock structure.
- Surrounding containers with an impermeable backfill.
The process of selecting deep geological repositories is under way in several countries (see table). Finland and Sweden are well advanced with plans for direct disposal of used fuel, since their parliaments decided to proceed on the basis that it was safe, using existing technology. Both countries have selected sites, in Sweden, after competition between two municipalities.
The UK’s radioactive waste disposal process stalled in late January after conflicting votes between regional and local government. The Borough of Copeland voted to continue exploring its suitability, but it lies within Cumbria County, which voted against the idea. The site selection process is based on a principle of voluntarism under which communities explore their options and have the right to withdraw at any time. The same approach has been practiced with success in Finland and Sweden to find suitable and welcoming places for radioactive waste disposal. It’s also the approach now favored by the U.S. Energy Department, as outlined in its January announcement. The negative vote in Cumbria now means that “the current process will be brought to a close,” said the UK Department of Energy and Climate Change, which “will now embark on a renewed drive” to find other interested communities that may be able to host a disposal site.
Canadian Nuclear Waste Disposal
Canada’s Nuclear Waste Management Organization (NWMO) was set up under the 2002 Nuclear Fuel Waste Act by Ontario Power Generation (OPG), Hydro-Québec, and New Brunswick Power Corp. operating in concert with Atomic Energy of Canada Ltd. (AECL). Its mandate is to explore options for storage and disposal, make proposals to the government, and implement what is decided. Less than 3,000 metric tons of used fuel per year from Candu reactors is involved. The nuclear utilities and AECL remain responsible for low- and intermediate-level wastes, which are currently stored above ground.
OPG in 2005 moved ahead with plans to build a deep geological repository for its LLW and ILW near the Bruce Nuclear Generating Station on Lake Huron. The facility will be 2,000 feet beneath OPG’s Western Waste Management Facility, which it has operated since 1974. Operation is expected to begin around 2017/18.
In June 2007, the government selected the retrievable deep geological disposal option, referred to as adaptive phased management, recommended by the NWMO for the long-term management of HLW. The NWMO has said that a final repository would probably be in Ontario, Québec, New Brunswick, or Saskatchewan, and host localities would need to volunteer for the role. Operation is expected by around 2025.
French and German Nuclear Waste
Radioactive waste management in France is governed by a 2006 law, which requires the updating every three years of a National Plan for the Management of Radioactive Materials and Waste. It confirms that long-term management of HLW would be by deep geological disposal (with retrievability for at least 100 years). The 2006 law envisages an operational solution for deep geological disposal to be available by 2025. The site is likely to be at Bure, where an underground laboratory in a clay formation was opened in 2004.
Germany has a nuclear phaseout policy in place, which, if not reversed, would result in all nuclear power stations being closed by around 2021. German policy had been to reprocess used fuel, but it has shifted toward direct disposal. Vitrified HLW from France and the UK is temporarily stored at facilities in Gorleben and Ahaus. HLW from reprocessing is stored at the facilities where they were created. The Morsleben repository for radioactive waste was used for the disposal of LLW and ILW in the former German Democratic Republic from 1971 to 1991 and later from 1994 to 1998. That installation is now being decommissioned. A former iron ore mine, Konrad in Salzgitter, has been investigated since 1975 as a possible repository for radioactive waste with negligible heat generation.
Japanese Nuclear Waste
Japan has a policy of reprocessing, and a large reprocessing complex at Rokkasho-Mura, Aomori Prefecture is under construction. A large LLW center at the Japan Nuclear Fuel Ltd. (JNFL) site in Rokkasho-Mura has been operational since 1992. JNFL is a private venture led by 10 domestic electric power companies.
Deep geological disposal is the preferred option for HLW. A site selection process for a final repository is under way by the Nuclear Waste Management Organization of Japan. Site selection could take place between 2023 and 2027.
Hungarian Facility Crosses the Finish Line
After 15 years of work and an investment of more than $300 million, the first disposal chamber at the Bataapati storage facility in southern Hungary was completed in early December. The project was built by the country’s Public Limited Co. for Radioactive Waste Management (known as Puram). Underground disposal vaults at Bataapati will eventually hold all the low-level and short-lived intermediate-level radioactive wastes left over from the operation and decommissioning of the Paks nuclear power plant.
As part of the repository inauguration in December, the first concrete container holding nine drums of waste was moved from a temporary surface storage facility. Once the facility is fully operational, waste drums will be stacked 650 to 800 feet underground inside granite bedrock caverns. Bataapati’s modular design will allow for its expansion should the Paks plant be granted a 20-year license extension and if Hungary decides to construct new reactors.
—David Wagman is executive editor of POWER.