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2 Spent Nuclear Fuel and End Points This chapter describes sources, inventories, and end points for spent nuclear fuel in Russia and the United States. 2.1 SPENT NUCLEAR FUEL IN THE RUSSIAN FEDERATION According to the Russian Federation law “On the Use of Atomic Energy,” irradiated nuclear fuel is considered a valuable raw material for recovery of nuclear fuel components and certain isotopes. At the same time, irradiated nuclear fuel is a potentially hazardous product as well as a potential source of plutonium, which is a proliferation risk. At the end of 2001 there were 13,515 metric tons of heavy metal (MTHM) of irradiated nuclear fuel at the Russian nuclear power plant and radiochemical plant storage facilities (Shatalov 2002) (see Tables 2.1 and 2.2). The annual growth of the SNF inventory in Russia is about 850 MTHM, nearly all from nuclear power operations in Russia, Ukraine, and Bulgaria. The total radioactivity of spent nuclear fuel accumulated in Russia comprises about 4.65×109 curies (Ci). 2.1.1 Power-Reactor Spent Fuel in the Russian Federation Of the four types of power reactors that operate in Russia, two types generate most of the power: boiling water graphite reactors (the RBMK reactors), and pressurized water reactors (the VVER reactors). RBMK-1000 reactors use UO2 fuel pellets containing 2.0–2.4 percent U-235 (the fissile isotope of natural uranium). The pellets are sealed in zirconium alloy rods, which are bundled into assemblies of 18 rods. Each assembly is inserted into a pressure tube or coolant channel. Water flow through a
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coolant channel can be stopped during reactor operation, allowing for online refueling. RBMK fuel enriched to 2 percent typically reaches an average burnup of about 30,000 megawatt days per metric ton of heavy metal (MWd/MTHM).1 The VVER reactors operate with UO2 fuel enriched to 3.0– 4.4 percent,2 sealed in zirconium alloy rods. The VVER rods are roughly half the length of RBMK assemblies. The rods are removed during refueling outages, one to two years apart (depending on fuel enrichment). VVER fuel typically reaches an average burnup of approximately 50,000 MWd/MTHM in a VVER-440 and 40,000–45,000 MWd/MTHM in a VVER-1000. The other two types of reactors are the liquid metal fast reactors (BN series), only one of which, the BN-600, now operates as a commercial power reactor, (the BOR-60 operates as a pilot power station), and the Bilibino boiling water graphite reactors (EGP-6 reactors), which are small versions of the RBMK reactors. The BN-600 at the Beloyarsk nuclear power station is cooled with sodium and has steelclad UO2 fuel, enriched to 17–33 percent. Six VVER-440 reactors (pressurized water reactors) operate in Russia and generate 87 MTHM of SNF annually. After discharge from the reactors, the SNF is stored in cooling pools for a period of 3–5 years, and then it is shipped in casks to the reprocessing plant, RT-1, at PA “Mayak.” The cooling pools at the reactor sites are typically filled only to 20–25 percent of their capacity. If shipments of the SNF offsite were to halt, however, the pools would be filled in four to five years. Breached SNF assemblies (now numbering 60) from VVER-440 reactors are stored in separate sections of the cooling pools. These assemblies are expected to be shipped to the RT-1 plant for reprocessing by 2007. Another 21 VVER-440 reactors operate in European countries outside of Russia. Shipments of VVER-440 SNF from these countries to Russia have diminished in recent years. As noted earlier, Russia intends to take back the SNF from those reactors, and is currently storing and reprocessing SNF from at least some of them for a fee. Seven VVER-1000 reactors operate in Russia and generate 190 MTHM of SNF annually. Another 17 VVER-1000 1 The theoretical maximum burnup for fuel of this composition—that is, the energy released if every nucleus of uranium were fissioned—is approximately 940,000 MWd/MTHM. 2 Enrichment is 3.6 percent on average for VVER-440s and either 3.3 or 4.4 percent for VVER-1000, depending upon the length of the operating cycle (Rosenergoatom 2002).
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TABLE 2.1 Data on SNF Inventory in Russia Nuclear Power Plants and Other Nuclear Facilities SNF Inventory at the End of 2001, MTHM Reactor Type Number of Operating Reactors Leningrad 3,720 RBMK-1000 4 Smolensk 1,830 RBMK-1000 3 Kursk 3,230 RBMK-1000 4 Total RBMK 8,780 11 Balakovsk 344 VVER-1000 4 Kalininsk 172 VVER-1000 2 Novovoronezh 163 VVER-1000 1 Rostova VVER-1000 1 Total VVER-1000 679 8 Novovoronezh 71 VVER-440 2 Kolsk 112 VVER-440 4 Total VVER-440 183 6 Bilibinsk 123 EGP-6 4 Beloyarsk 59 BN-600 1 190 AMB Total Nuclear Power Plants 10,020 30 PA “Mayak” 486 NA Krasnoyarsk MCC 2,840 NA NIIAR 122 NA Kurchatov Research Center 3 NA IPPE 14 NA NIKIET 1 NA Tomsk SCC 32 NA Total for Russian Federation 13,520 aRostov is a new power plant and no SNF had been discharged as of the end of 2001. SOURCE: Shatalov (2002).
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TABLE 2.2 Aggregated Data for the End of 2001 on Amounts of Spent Nuclear Fuel and Radioactive Waste at Nuclear-Powered Submarines (NPSs) Destined for Dismantling, Floating Technical Bases, Shore Bases, and Plants Carrying Out Dismantling Work Object name Units NPS Compartments Quantity of Solid RW Quantity of Liquid RW Total Activity Number Number Ci m3 Ci m3 Ci Ci NPSs with unloaded SNF 29 18,000 3.0×106 1,200 12 3.0×106 NPSs awaiting unloading of SNF 93 170 1.8×108 54,000 1.7×107 3,600 36 2.0×108 Floating technical bases 41 20 2.0×107 3,600 30 2.0×107 Shore bases of northern Region 2 116 5.0×107 4,600 6.0×103 3,200 60 5.0×107 Shore bases of Pacific Region 2 40 2.0×107 15,550 1.6×105 2,100 40 2.0×107 Plants that dismantle NPSs 8 2,000 3.0×102 2,500 30 3.3×102 SOURCE: Shatalov (2002).
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annually. Another 17 VVER-1000 reactors operate outside of Russia, and several others are in the design and construction stage. Spent fuel from VVER-1000 reactors is not currently reprocessed: After 3–5 years of storage in cooling pools at the power plants, the assemblies are shipped to a centralized storage facility at the Krasnoyarsk MCC. Eleven RBMK-1000 reactors operating in Russia generate 550 MTHM of SNF (about 5,000 fuel assemblies) annually. Two AMB reactors (earlier versions of the RBMK reactor), located at the Beloyarsk nuclear power plant, were decommissioned in 1983 and 1990 (IAEA 2001). Four EGP-6 reactors (graphite-moderated boiling-water reactors for combined heat and power, each generating 62 MWth) located at one power station in Bilibino are planned to be finally decommissioned in 2004. Unit 3 of the Beloyarsk nuclear power station is a BN-600 reactor. The BN-600 has operated since 1980, producing roughly 3.8 MTHM of SNF per year (CEG 2000), and is licensed to operate through 2010. The SNF from this reactor is reprocessed at RT-1. 2.1.2 Government-Managed Spent Nuclear Fuel in the Russian Federation Management of SNF from weapons production, naval vessels, and research reactors is paid for by the federal government. Weapons-Production Spent Nuclear Fuel Three dual-purpose reactors (production of plutonium and power) still operate in the Russian Federation: one at the Krasnoyarsk MCC and two (ADE-4 and ADE-5) at the SCC. These reactors continue to operate because the nearby cities need the heat and electricity that the reactors produce. The fuel from these reactors does not accumulate because it is reprocessed at onsite facilities. Roughly 1.5 MTHM of plutonium are generated by these reactors (500 kg each) annually and placed in storage as an oxide (Diakov 1995). Reprocessing of this SNF generates liquid and solid radioactive wastes.
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Maritime Spent Nuclear Fuel As noted earlier, the Soviet Navy launched some 248 nuclear-powered ships, including 244 submarines, most powered by two reactors.3 The other vessels were cruisers and research and support vessels. As of July 2002, 190 Russian submarines have been retired from service. The majority of these, 114, are from the Northern Fleet and sit in various conditions at the bases along the shore of the Kola Peninsula. The remainder, 76, are from the Pacific Fleet at bases along the coast of Vladivostok (54 in Primorsky region) and on the Kamchatka Peninsula (22 in Kamchatka). By early 2001, about 70 tons of SNF (including breached assemblies) had accumulated from the transport nuclear installations at the Russian Navy’s shore bases and floating technical bases (a refueling and service ship). The total radioactivity of that accumulated SNF is estimated to be 200 million curies. The status of many assemblies is unknown. As part of decommissioning of nuclear submarines, the unloaded reactor compartments (along with adjacent compartments that add buoyancy) are cut from the rest of the vessel, and are left floating, moored in place, for storage. Beginning in 2002, the rate at which SNF is unloaded from operating and decommissioned transport installations is expected to be in the range 15–18 NPSs per year. The SNF from nuclear-powered ships in Russia is generally described as reprocessible or unreprocessible. The latter category includes defect fuel, damaged fuel,4 fuel encased in solidified metal coolant, and fuel for which existing reprocessing facilities do not have appropriate process lines due to the fuel’s composition (e.g., U-Zr and U-Be fuel). Reprocessing of defect fuel requires new technological solutions (control systems, packaging in tight containers, development of the method for reprocessing in containers). Reprocessing of defect fuel is to be taken into account when the RT-1 undergoes plant reconstruction (planned for 2005–2007). According to the Russian strategy for SNF management (CEG 2000), damaged cores will stay at the na- 3 Forty-six Soviet submarines, including mini-submarines, were built with only one reactor each. Seven of these were built with liquid-metal-cooled reactors (LMRs), rather than the standard pressurized-water reactors (PWRs), using leadbismuth eutectic (a prototype LMR submarine had two reactors) (Nilsen et al. 1996). 4 Defect fuel includes assemblies with structural damage (swelling, bending, leakage, etc.). Damaged fuel is fuel that was damaged as a result of an accident and now is not retrievable from the cores.
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val bases until the cores can be safely disposed.5 Reprocessible fuels are planned to be transported to PA “Mayak” for radiochemical reprocessing. The defect fuel is also planned to be reprocessed after storage. Plans are not yet in place for unreprocessible fuel. Northern Fleet6 As noted previously, 114 nuclear-powered submarines (NPS) had been decommissioned from the Russian Navy in northwestern Russia, as of July 2002. Seventeen NPSs will be defuelled in 2002. Defueling of NPSs currently designated for decommissioning is anticipated to be completed by 2007. Two stand-prototypes (on-land test reactors) of the shipbased nuclear power plants are in operation in Russia, in Obninsk. The SNF from these stand-prototypes, totaling several tons, is stored in cooling ponds at the sites. Three stand-prototypes of space nuclear power installations were also constructed and operated in Russia. The SNF from these reactors (about 500 kg) is stored in dry storage facilities at the sites. Research and Test Reactor Spent Nuclear Fuel According to the IAEA research reactor data base (1999b), there are 51 research reactors in the Russian Federation: 28 operating, 12 decommissioned, and 11 shut down. At least one of the reactors reported as operating has since shut down (Bellona 2002). In addition, there are 46 critical assemblies: 29 operating and 17 shut down. Kozlov et al. (2002) report an inventory of roughly 28,500 spent fuel assemblies at 24 of the research reactors. Fourteen research reactors outside of Russia expect to send their SNF to Russia for disposition. Because of the diversity in the construction of the fuel rods and fuel assemblies and differences in fuel composition and structural materials, a decision will be made for each research re- 5 An alternative for management of damaged cores is placing cut-off reactor compartments in inactive, large-diameter strategic missile compartments. The method proposed would, it is hoped, safely isolate damaged reactor compartments from the biosphere for at least 25 years. (Ruzankin and Makeyenko 2000). 6 Limited time and resources prevented the committee from addressing the situation in the Pacific Fleet in any detail.
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actor and assembly (critical and subcritical) selecting between reprocessing, long-term storage, and disposal for the SNF. 2.2 SPENT NUCLEAR FUEL IN THE UNITED STATES As of December 31, 2001, the United States was storing approximately 45,000 MTHM (Holt 2002)7 of spent fuel from its civilian nuclear power plants at reactor sites and at centralized facilities8 (see Table 2.3) for eventual disposal in a geologic repository, and is producing new commercial SNF at a rate of about 2,000 MTHM per year. A smaller amount of spent fuel from the weapons program is also being stored for eventual disposal, but most has been chemically processed to recover plutonium, highly enriched uranium (HEU), or Np-237. The United States does not now reprocess its spent fuel from civilian nuclear power plants, so the current form of the SNF is the form that is to be disposed of in an underground geologic repository. 2.2.1 Power-Reactor Spent Nuclear Fuel in the United States Production of nuclear power for civilian use and production of plutonium for nuclear weapons have mostly been separate in the United States.9 Spent nuclear fuel from commercial power reactors (commercial SNF) constitutes the largest source and stockpile of SNF in the United States. This is due to the scale of the U.S. nuclear power enterprise (103 reactors generating 87.8 GWe 7 DOE last updated its comprehensive inventory in 1999 (EIA 1999a), so information on the current inventory is scarce. The 1999 inventory provides the data for Table 2.3. 8 Two centralized storage facilities—one in West Valley, New York, and another in Morris, Illinois—currently have SNF. Another has been proposed, called Private Fuel Storage (PFS), in Skull Valley, Utah. At West Valley, the fuel has been loaded into dual-purpose casks (storage and transportation) and awaits shipment to INEEL for interim storage. 9 The most notable exception is the N-Reactor at Hanford, which produced more weapons plutonium than any other reactor in the United States, and also generated electricity. Some experimental reactors generated electricity for use by DOE facilities.
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TABLE 2.3 Summary of Current Locations of Spent Nuclear Fuel and High-Level Radioactive Waste in the United Statesa, b (*Denotes decommissioned reactors) State Commercial Reactors (MTHM in Storage) Non-DOE Research Reactors Navy Reactor Fuel DOE-Owned Spent Fuel & HLW Surplus Plutonium Alabama Browns Ferry 3 units (1,032); Farley 2 units (758) Arizona Palo Verde 3 units (812) University of Arizona, Tucson Arkansas Arkansas Nuclear 2 units (730) California Diablo Canyon 2 units (578) Rancho Seco 1* 1 unit (228) San Onofre 1*,2,3 3 units (802) Humboldt Bay * 1 unit (28.9) University of California, Irvine; General Electric (1 research, 2 research & test*, 1 power*); McClellan Air Force Base (now UC Davis); General Atomics - MARK 1* - MARK F*; Aerotest Research Colorado Fort St. Vrain* (see DOE-owned fuel) U.S. Geological Survey Fort St. Vrain* (15.4) Rocky Flats Environmental Technology Site Connecticut Haddam Neck* 1 unit (412) Millstone 1*,2,3 3 units (1061) Florida Crystal River 1 unit (316) St. Lucie 2 units (715) Turkey Point 2 units (720) University of Florida, Gainesville Georgia Hatch 2 units (889) Vogtle 2 units (489) Georgia Institute of Technology* Idaho Idaho State University, Pocatello Naval Reactors Facility (19.5) Idaho National Engineering & Environmental Laboratory (INEEL) (273) INEEL
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State Commercial Reactors (MTHM in Storage) Non-DOE Research Reactors Navy Reactor Fuel DOE-Owned Spent Fuel & HLW Surplus Plutonium Illinois Clinton 1 (207) Quad Cities 2 units (925) Braidwood 2 units (448) Zion 2 units* (1018) Byron 2 units (543) Dresden 1,* 2, 3 (950) LaSalle County 1, 2 (555) General Electricc (674) University of Illinois, Urbana - Triga* - Lopra* Argonne National Laboratory East (0.14) Indiana Purdue University Iowa Duane Arnold (301) Iowa State University,* Ames Kansas Wolf Creek (308) Kansas State University (Manhattan) Louisiana Waterford 3 (287) River Bend 1 (255) Maine Maine Yankee* (542) Maryland Calvert Cliffs 1, 2 (741) University of Maryland, College Park; National Institute of Standards and Technology; Armed Forces Radiobiology Research Institute; U.S. Army Aberdeen Proving Grounds Massachusetts Pilgrim 1 (362) Yankee-Rowe* (127) Massachusetts Institute of Technology; University of Lowell; Worchester Polytechnic Institute Michigan Enrico Fermi 2 (235) Cook 1,2 (885) Palisades (387) University of Michigan (Ann Arbor)
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State Commercial Reactors (MTHM in Storage) Non-DOE Research Reactors Navy Reactor Fuel DOE-Owned Spent Fuel & HLW Surplus Plutonium Michigan Big Rock Point* (58) Dow Chemical Company (Midland) Minnesota Monticello (193) Prairie Island 1, 2 (576) Mississippi Grand Gulf (445) Missouri Callaway 1 (359) University of Missouri (Columbia) University of Missouri (Rolla) Nebraska Cooper (233) Fort Calhoun (256) Veterans Administration (Omaha) New Hampshire Seabrook (172) New Jersey Oyster Creek (438) Salem 1, 2 (625) Hope Creek (313) New Mexico University of New Mexico (Albuquerque) White Sands Missile Range Sandia National Laboratories -Annular Core Research Reactor -Sandia Pulse Reactor III (0.29) Los Alamos National Laboratory New York Nine Mile Point 1,2 (656) Indian Point 1*, 2, 3 (757) Fitzpatrick (415) Ginna (311) Shoreham* (0) State University of New York* (Buffalo) Cornell University -TRIGA Mark II -Zero Power* (Ithaca) Manhattan College* (Bronx) Rensselaer Polytechnic Institute (Troy) Brookhaven National Laboratory, including -High-Flux Beam Reactor* -Brookhaven Medical Research Reactor (0.06); West Valley Demonstration Projectd (26.8) North Carolina Brunswick 1, 2 (486) Harris (693) McGuire 1, 2 (848) North Carolina State University (Raleigh) Ohio Davis-Besse (315) Perry (276) Ohio State University (Columbus);
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Handling and operations.” This presents several tradeoffs regarding types of hazards: radiological, safeguards and proliferation, and criticality. Both the United States and Russia are investigating partitioning and transmutation. The United States is doing so in the Advanced Fuel Cycle Initiative and Russia in its on going examination of fuel cycles involving fast reactors and reprocessing spent nuclear fuel. must be removable so as to allow for an overhead crane to maneuver the fuel assemblies and any containers in which they are stored. The water is actively cooled by pumping it through a heat exchanger. The racks that hold fuel assemblies in spent fuel pools are configured to prevent criticality and, if the geometry itself is insufficient, plates loaded with boron are placed between the assemblies or boric acid is added to the water to absorb neutrons. The water chemistry is actively controlled to maintain the boron concentration in the water, to reduce the rate of corrosion of the fuel cladding, and to remove radionuclides that might have leaked through failed cladding. Dry storage can be in vaults, silos, or casks17 and relies on air or inert gases (such as nitrogen, or helium) to provide cooling. Dry storage is most appropriate for SNF that is past the initial period after removal from a reactor when its heat-generation rate is highest. In most dry storage designs, the spent fuel assemblies (SFAs) are sealed in an inert atmosphere inside a steel canister that is welded shut. Vaults are typically concrete structures with many compartments to hold the canisters. The canisters prevent release of radioactive dust and volatile fission products and protect the fuel from chemical reaction. Cooling is accomplished by either forced or natural air convection around the canisters and biological shielding is provided by the concrete structure. Vaults generally rely on geometry to prevent spontaneous chain reactions (criticality events). Silos are concrete cylinders that serve as sleeves for canisters, emplaced either vertically or horizontally, providing shielding and physical protection for the fuel. Vertical silos typically ac- 17 The translation of the Russian terminology to English results in vaults being referred to as chambers and silos as reinforced concrete massifs. Rather than adopt one over standard usage over the other, the standard terminology is kept and the difference is noted.
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commodate several canisters in one concrete cylinder. Silos rely on passive convective airflow along the outside of the sealed canisters to provide cooling, and so have holes for inlet and outlet of the air. Silos are constructed on a concrete pad. Dry storage casks are combined systems that provide shielding and prevent releases of radioactive materials and are moved as integral units. Spent fuel assemblies can be loaded directly into the casks, which are typically made of steel or steel-reinforced concrete with a steel liner. The limited number of assemblies in each cask or silo, and the lack of water acting as moderator surrounding the SNF reduce the concerns about criticality (unless the fuel is highly enriched). Borated steel plates are still, nonetheless, commonly used as a safety measure, particularly for casks that are loaded under water. Some casks can be used for both transportation and storage (dual-purpose casks). Both wet storage and dry storage have excellent safety records, although there is the potential for storage pools to lose their water as a result of leaks, and thereby lose their shielding and cooling. Dry storage has increased in popularity among reactor operators as demand for storage capacity beyond that available in the at-reactor storage pool has increased. In these cases, older fuel can be loaded into dry storage. Both the initial capital costs and the continuing operating costs of dry storage are lower than for wet storage. Some forms of storage, such as interim storage in the reactor compartments of decommissioned submarines, storage in maintenance vessels, and storage in the open air, are undesirable. These are not safe and secure forms of storage, so they are not appropriate end points, interim or final. Storage of Spent Nuclear Fuel in Russia In Russia, cooling pools at nuclear power plants are designed, as a rule, for a three-year storage period during which the heating from radioactive decay drops dramatically (e.g., by a factor of nearly 12,000 for VVER-1000 SNF). Then the fuel is transported for reprocessing or interim storage. Spent fuel from VVER-440 reactors and the BN-600 reactor is sent for reprocessing to the RT-1 plant at PA “Mayak,” where it is stored in a large pool until it is chopped up and reprocessed in the plant.
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More than 8,700 MTHM of RBMK SNF with total radioactivity of 3.1 billion curies are stored in cooling pools at the power plants and at separate wet-storage facilities onsite. At the Leningrad Nuclear Power Station, for example, fuel is stored for three to five years in the cooling pool adjacent to the reactor building, then is loaded into a cask full of water and moved to a storage building nearby on the site (NAS 1990). Approximately 3,000 fuel assemblies are breached, which complicates handling and storage. Dry storage is expected to replace pool storage for all of the fuel in coming years. It is anticipated that the roughly 8-meter-long RBMK fuel assemblies will have to be cut in two to fit inside the dry storage casks. Russia does not currently ship any RBMK SNF, with the exception of transportation of half-assemblies for post-reactor tests in hot cells. The decision on the long-term plan for RBMK fuel management has not been made yet. Several approaches are possible and are now under consideration. Although accumulation of RBMK SNF at the power plant site can lead to difficulties when the plant is to be decommissioned,18 this spent fuel is not seen as a proliferation or an immediate health hazard, so it is the committee’s judgment that leaving it in place is a reasonable allocation of scarce resources. Nevertheless, to prevent theft for possible use in a radiological weapon, this spent fuel must be protected at the sites. At present, approximately 1,500 VVER-1000 fuel assemblies (about 680 MTHM) with total activity of 600 million curies are stored in cooling pools at the power plants, which are about 40 percent full. In addition, there is a centralized wet-storage facility for VVER-1000 fuel at the Krasnoyarsk MCC. This centralized facility has a storage capacity of 15,000 fuel assemblies (about 6,000 MTHM), which is about 37 percent filled today. Moreover, an unfinished part of the facility has a capacity of up to an additional 3,000 MTHM. The VVER-1000 SNF cannot be reprocessed at RT-1 unless upgrades are made to one of the process lines. The RT-2 plant that was planned to be built at the Krasnoyarsk MCC was designed to process VVER-1000 SNF and other fuels. Some structures were built for RT-2 before the project was halted for lack of funds, and these are now being adapted for storage. Once modernized, the facility capacity will be increased up to 9,000 MTHM. About 50 breached VVER-1000 fuel assemblies are 18 In particular, a tariff on nuclear power plant operations provides funds for management of SNF. These funds are not available after decommissioning.
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currently stored in separate sections of the pools at the power plants, and are planned to be shipped to RT-1 by 2007. There are now plans to construct a wet-storage facility with a capacity of 1,700 MTHM at PA “Mayak.” The SNF from the Beloyarsk nuclear power plant was unloaded and kept in dry storage at the site (190 MTHM of SNF in 5,000 fuel assemblies) and in the PA “Mayak” cooling ponds (76 MTHM of SNF in 2,200 fuel assemblies). Most of these fuel assemblies are breached. The Bilibino power station has accumulated 164 MTHM (6,500 assemblies) of SNF, none of which are breached. Some of this SNF has already been transferred to a dry storage facility at the power plant site. As mentioned above, Minatom is currently considering adding new dry-storage facilities using the uncompleted buildings at the site of RT-2. The facility would be financed by Rosenergoatom. A decision has been made that it should be a vault-type (chamber-type) storage facility with a capacity of 33,000 MTHM. To provide interim RBMK SNF storage at the power plant sites, dual-purpose casks, the TUK-104 and TUK-109 with capacities of 114 and 144 irradiated half-assemblies of RBMK-1000 fuel, have been developed. The same casks can be used to transport SNF to a centralized facility. Russia is studying the condition, possible degradation modes, and maximum thermal loads of its irradiated SNF in order to develop its dry-storage capabilities. In particular, studies focus on the condition of structural materials in irradiated fuel assemblies that have been in wet storage, and on how these materials might degrade in dry storage. Quantitative models for assessing the thermal conditions and material behavior are being developed so that appropriate storage regimes (temperatures, environment, etc.) can be selected. Spent nuclear fuel from the Northern Fleet’s NPSs that has not yet been shipped for reprocessing at PA “Mayak” is currently stored in shore technical bases at Andreeva Bay and at the Gremikha settlement, as well as in storage tanks of floating technical bases (FTBs), and on board decommissioned NPSs. A technical base is a facility for servicing, fueling and defueling, and decommissioning and dismantling of nuclear-powered submarines. In 1998, there were about 8,300 SFAs of reprocessible SNF stored at naval FTBs, NPSs that await defueling, and FTBs for the nuclear-powered ice-breaker fleet. The total of defect fuel, which is unreprocessible, at coastal technical bases was about 4,400
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SFAs. The problems associated with storing the cores from nuclear-powered submarines are mostly due to the lack of needed infrastructure (i.e., lifting and transport facilities, coastal structures, and interim regional storage facilities that are insufficient both in number and in capacity). But it is also true that many of the SFAs in storage and the storage facilities themselves, particularly the FTBs and NPSs, are in very poor condition and constitute serious hazards. Andreeva Bay hosts the largest SNF-storage facility in the region. The facility operated a storage pool until 1983 when, as a result of the poor condition of the facility, it was decided to construct a temporary facility for short-term (three to four years) dry storage and to transfer the stored SNF to this new facility (Bøhmer et al. 2001; Nilsen et al. 1996). The short-term storage facility has been in operation for over 18 years. The facility is now full, but it would not be able to accept new SNF in any case because of structural shortcomings and because the facility does not comply with current safety requirements (Bøhmer et al. 2001; Ivanov et al 1999). A total of 21,640 SFAs are stored at the shore technical base at Andreeva Bay, including 220 SFAs that are stored in containers that sit in an open area (not enclosed in a building) (Bøhmer et al. 2001). The Gremikha settlement hosts the Northern Fleet’s second largest storage facility for SNF. The facility was planned to store SNF from light-water reactors of the first generation of NPSs and spent retrievable elements from NPSs with liquid-metal-cooled reactors. The storage facility consists of drained cooling ponds (100 SFA), containers in an open-air site (700 SFA), and a concrete shaft for retrievable elements of reactors with liquid-metal coolant (6 units). The facility is in a generally poor state. At present, two Project 2020 FTBs (Malina class service ships) are the only ones available in the Northern Navy and capable of executing all of the steps from unloading of SNF from NPS reactors to transferring the fuel for railway transport (Ivanov et al. 1999). One FTB is at the shore base in Olenya Cuba (Kola Peninsula) and the other one is in the area of Severodvinsk (Arkhangelsk region). Each FTB has tanks in which operators store containers of SFAs. The number of SFAs that a tank holds depends on the characteristics of the SFAs, but each FTB can store the SNF from two NPSs (Ivanov et al. 1999). The actual inventory at
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any given time varies depending upon the refueling, defueling, and storage demands. The civilian ice-breaker fleet of the Murmansk Shipping Company has three of its own FTBs, which store the fleet’s SNF. The ships are Imandra, Lotta, and Lepse. All of these FTBs are moored at the Repair-Technological Enterprise “Atomflot.” The storage tanks on Imandra can accommodate up to 1,530 SFA, or about 6 cores from the ice-breaker reactors (Bøhmer et al. 2001; Nilsen and Bøhmer 1994). Imandra has also been used to defuel NPSs from the Navy (Bøhmer et al 2001). Lotta uses dry storage to accommodate as many as 4,080 SFAs loaded into containers, although some of that total is devoted to unreprocessible SFAs that are stored until a disposition path is found (Bøhmer et al. 2001; Nilsen and Bøhmer 1994). Lepse, the oldest of these FTBs, was used until 1980 for reloading of nuclear fuel and for storage of fresh and spent nuclear fuel from nuclear-powered icebreakers Lenin, Arktika, and Sibir. Lepse, unlike the other FTBs, stores each of its approximately 640 SFAs in a separate cell. The cell cannot be removed without disturbing the ship’s structure. All of the SNF on Lepse is over 20 years old, and although the cells were filled with water during earlier operations, the SFAs are now stored dry. During the years of wet storage, the SFAs corroded enough to change their geometry and now cannot be removed from the cells, so all of Lepse’s SFAs are deemed “non-retrievable” (Ruzankin and Makeyenko 2000; Safutin et al. 1999). Lepse was decommissioned in 1988 and moored in place in 1990. In 1991, in order to provide additional shielding, the space between the SNF storage tanks was filled with special concrete mixtures (Bøhmer et al. 2001). About 60 decommissioned NPS containing roughly 26,000 SFAs (as of 2001) sit floating near the coastal bases and await defueling (Bøhmer et al. 2001; Sinisoo 1995; Alekseyev 2001). This is the equivalent of about 110 cores. Decommissioned NPS are not well prepared to sit afloat for long periods without regular maintenance (Ruzankin and Makeyenko 2000), and the older ships (those that have sat for over 10 years), which total roughly 30 (Atomic Chronicle of Russia 2000), pose the greatest potential radiological hazard. Because of the much higher enrichment in maritime fuel compared with power reactor fuel, this SNF must be included in a MPC&A program. Plans have been developed for a repository for interim storage of SNF from NPSs and for disposal of other nuclear materials on the Kola Peninsula.
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Storage of Spent Nuclear Fuel in the United States The majority of U.S. SNF is that generated at commercial power reactors. Most of this SNF is stored at the generation sites, either in pools or in dry-storage casks. As of December 31, 2001, there were 3,000 MTHM of spent fuel in dry cask storage and 42,000 MTHM in pool storage, for a total of 45,000 MTHM (Holt 2002). Sixteen power-plant sites and two DOE facilities are licensed by the U.S. Nuclear Regulatory Commission for dry-cask storage (U.S. NRC 2001). Each kind of dry storage facility—vaults, silos, and casks (chambers, reinforced massifs, and casks)—has been built in the United States (Bunn et al. 2001). Some SNF, particularly from older reactors, was shipped for storage offsite at independent spent fuel storage installations in Illinois at the Midwest Fuel Recovery Plant (674 MTHM) and in New York at the West Valley Demonstration Project (26 MTHM). Some SNF seen as special cases are stored in Idaho at INEEL (171 MTHM and at other DOE facilities (26 MTHM) (DOE 2002a). Several older commercial reactors had their SNF reprocessed at West Valley, and a small amount was reprocessed at SRS. Some DOE-managed SNF is undergoing modest treatment to allow for safe storage, packaging, and disposal. Nearly 85 percent of this set is spent fuel from the N-Reactor at Hanford, some of which is highly corroded. Most of the irradiated N-Reactor fuel (roughly 2,100 MT containing 4 MT of plutonium, 105,000 assemblies, amounting to 55×106 Ci) is stored in the K-East and K-West Basins (cooling pools) along with a small amount (974 fuel elements) of SNF from the older reactors at Hanford (Gerber 2001; DOE 2000c). N-Reactor fuel is solid uranium metal with zirconium-alloy cladding, and the SNF in the K-Basins has been stored for 15 to 31 years. The SNF from the older “single-pass” reactors is aluminum-silicon clad. Some of the N-Reactor SNF was damaged (breaks in the cladding) during discharge and, over the years, water has seeped in and oxidized some of the fuel, causing it to swell and damage the cladding. The oxidized fuel sloughs off and accumulates as sludge in the canisters. The SNF has been visually inspected and the following assessment found in DOE (2000c, DOE 2002b) was made (see Table 2.5). “Intact fuel” has no evidence of cladding breach of deposited sludge; “breached fuel” has minor cladding ruptures with no
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TABLE 2.5 Assessment of Fuel Stored in the K Basins Damage Category K West Basin K East Basin Intact fuel 50% 49% Breached fuel 39% 9% Defected fuel 0% 38% Bad fuel 11% 4% SOURCE: DOE (2002b). reacted fuel or deposited sludge visibly present; “defected fuel” has definite evidence of cladding breach with reacted fuel escaping as oxide or sludge from the element; and “bad fuel” has gross cladding failure with substantial element dilation, clad splitting, element deformation, or fuel void. Exposed fuel has contaminated the water in the pools. The SNF in the K-East Basin (51,000 assemblies) sits in 3,700 canisters that have no caps, so one or both ends of the canisters allow free flow of water. The K-East Basin walls and floors were not sealed before the fuel was loaded into the pool and water has leaked on two occasions: releasing approximately 5.4×104 m3 of contaminated water into the subsurface through a floor joint in the late 1970s, and releasing about 340 m3 in 1993 (Gerber 2001). The walls of the K-West Basin were coated with sealant and the cans in that pool are capped, so fewer problems are anticipated in treating that fuel. Treatment of the fuel involves several steps to be carried out under water: removing canister lids (if they are present), cleaning the fuel to remove corrosion products, loading the fuel into baskets and placing the baskets in a single 14-foot long, 2-foot diameter multi-canister overpack. The baskets are configured to prevent criticality, and specialized copper baskets have been designed to hold fuel scraps ranging from fines up to 3 inches across. (As of December 2002, the project had accumulated nearly 6 tons of fines.) The fuel is then dried, which is accomplished by cold vacuum drying. The canister is then shipped to a vault-type storage facility made of steel reinforced concrete. The storage facility will hold 400 of the multi-canister overpacks in 220 steel tubes that extend 12 meters below the facility floor. Passive cooling is provided by convective air flow (Gerber 2001). As of December 2002, 167 multi-canister overpacks had been loaded and all but 2 were in the storage facility. The fuel is to be stored for 40 years, or until a repository is available to accept the fuel for disposal.
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About 50 cubic meters of sludge with varied composition (uranium oxides and hydrides, cladding debris, and various corrosion products) has accumulated on the K-Basin floors, in the canisters, and in the basin pits. Over 80 percent of the sludge is in the K-East Basin. The current plan for this material is to package it and store it until a disposition path for the material is identified. The program to process the N-Reactor fuel and place it in dry storage had an ambitious schedule. All of the fuel was to be processed by the end of 2003. Early milestones were missed, but DOE has now treated most of the fuel from the K-West Basin and has transferred some of the fuel from the K-East Basin and treated it for storage. The committee notes that progress is being made on the K-Basin fuel, but thus far the program has only addressed the fuel that is in better condition. The more difficult work, dealing with the most damaged fuel in the K-East Basin and the fines and sludge, is still ahead. Other SNF, such as aluminum fuels from research reactors around the world and production reactors within DOE, require some kind of treatment to make them safe for storage and disposal. Workers at SRS, where DOE is gathering and storing the research reactor fuel, are developing a “melt and dilute” technology for the highly enriched aluminum SNF, termed “at risk” SNF because of security and criticality concerns. The sodium-bonded SNF from the Experimental Breeder Reactor-II is being treated using electrometallurgical processes (also called pyroprocessing) in an experimental apparatus at the Argonne National Laboratory West (DOE 2000d). DOE manages batches of fuel that must be treated as special cases. The most dramatic example that has already been treated is the 81.5 MTHM of fuel and fuel debris from the Three Mile Island (TMI) plant’s Unit 2 reactor, which underwent a partial core melt during an accident on March 28, 1979. Some of the fuel elements are in good condition, but others melted into a mixture of the fuel, cladding, control rods, burnable poisons, and other reactor components. Nearly all of the fuel and fuel debris from the accident is stored at INEEL, where it is being dried and transferred from pool storage to the TMI Dry Storage Facility. This fuel and fuel debris is currently planned to be disposed of in a geologic repository along with other spent fuel. Other fuel that has not yet been processed or treated includes fine particles from cutting SNF inside hot cells for assay, and the MSRE fuel, which is no longer molten.
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2.5.2 Disposal of Spent Nuclear Fuel and HLW The United States currently plans to dispose of commercial spent nuclear fuel directly, without chemical processing. The fuel assemblies are to be loaded into metal canisters, sealed, and shipped for disposal in a mined geologic repository. Under the Nuclear Waste Policy Act of 1982, the federal government is supposed to take title to this fuel and put it into a geologic repository. DOE is responsible for the disposal of commercial and defense SNF, as well as other HLW. To fund the commercial SNF portion of this program, a tax of 0.001 dollars per kilowatt-hour is placed on the electricity sold by each nuclear power station19 and some government funds have been appropriated from defense programs to cover approximately one-third of the program costs to date. It is this funding that has been used to investigate the Yucca Mountain site, in Nevada, as a possible location for the first HLW repository (see Sidebar 2.2). After two decades of study by the Department of Energy, the President of the United States approved the department’s proposal to apply to the Nuclear Regulatory Commission for a license to construct a repository at this site. The governor of the state of Nevada vetoed the proposal, but the United States Congress over-rode that veto. The official DOE program plan is to submit a license application by December 2004. The U.S. NRC would then take three years (possibly four) to review the application and to decide whether to grant authorization for construction. DOE hopes to have construction authorization by the end of 2007 and to open the repository in 2010. Most external commenters believe this ambitious schedule is unrealistic based on the time needed for each step. In addition, several lawsuits that attempt to block the various steps in the process have been filed. The spent fuel will sit in some form of interim storage until a repository is available. The generators of the commercial SNF have historically been responsible for the costs of storing the SNF prior to disposal, but as schedules for disposal of the SNF are pushed into the future, lawsuits have been filed demanding that DOE cover the costs. Courts are in the process of deciding on these lawsuits. 19 Only about half of the tax collected has been used for the disposal program, with the rest put into the U.S. Treasury for general purposes.
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SIDEBAR 2.2: The Planned Repository at Yucca Mountain Yucca Mountain is located about 160 kilometers northwest of Las Vegas, Nevada, at the western edge of the Nevada Test Site (where testing of nuclear weapons was carried out). The area surrounding the site is sparsely populated and receives an average of 17.0 centimeters of precipitation per year. The mountain is made up of a volcanic ash, called tuff, which was deposited approximately 12 million years ago. The mountain has been under investigation for over 20 years as a potential host for the first mined geologic repository for spent nuclear fuel and high-level radioactive waste (HLW) in the United States, and the Congress has given approval for DOE to proceed with a license application to construct the repository. The proposed design would place the repository in a layer of welded tuff in the unsaturated zone, approximately 300 meters below the surface and approximately 300 meters above the water table (i.e., above the saturated zone). The current design for the potential repository calls for spent nuclear fuel and high-level radioactive waste to travel to Yucca Mountain by truck or rail in shielded shipping containers. DOE has done only preliminary transportation studies, explicitly avoiding more detailed planning until after the site recommendation, which occurred in 2002. Once these materials arrive at the repository, they would be removed from the shipping containers and placed in double-layered, corrosion-resistant packages for disposal. The design lifetime of the disposal containers is required to be at least 1,000 years, and the current design utilizes an alloy (C-22) estimated to be corrosion resistant for at least 10,000 years. Rail cars would carry the canisters underground into the repository, and remotely controlled equipment would place the canisters on supports in drifts (side tunnels) off of a main underground tunnel. DOE is still exploring whether the plan should include backfilling the tunnels or ventilation should be maintained to keep the packages dry, and whether to keep the repository “hot” or “cold” (i.e., above or below the boiling point of water). An 8-kilometer-long tunnel called the Exploratory Studies Facility has been bored through the mountain at the depth where a repository would be constructed. Several tests continue at the site to gather data on water flow through the medium, on the behavior of the rock when it is heated (as it would be by the waste), and on other unresolved technical questions. Under the Nuclear Waste Policy Act, the law governing disposal of spent nuclear fuel and high-level waste, the first HLW repository in the United State will be allowed to accept no more than 70,000 MTHM of spent nuclear fuel and HLW until a second HLW repository is in operation. DOE has allocated space for 63,000 MTHM of commercial spent fuel and for 7,000 MTHM equivalent of DOE HLW and spent fuel. The 70,000 MTHM limit is not a technical capacity limit but a legislated limit.
Representative terms from entire chapter: