As the average age of American reactors approaches 40 years old, experts say there are no technical limits to these units churning out clean and reliable energy for an additional 40 years or longer. Thanks to research performed over the last decade by the U. Four utilities already announced plans to extend their operating licenses and six reactors have already been approved. The majority of these will expire in the s. Due to the amount of time it takes to prepare for regulatory reviews, utilities are now determining if they should apply for an additional 20 years of service.
This ranged from the reactor core and much of the equipment inside of it to the cabling and concrete around the plant. Even under the Lower Scenario, a steady increase in capacity projections is seen over the entire reporting period.
World reactor requirements for uranium estimated at about 62, tU in increase to 79, tU in and , tU in in the Reference Scenario; however, world uranium production dropped considerably from 63, tonnes of uranium tU in to 47, tU in Secondary supplies of uranium are projected to play a gradually diminishing role in the world market, and while commercial inventories will, in the near term, help in bridging the gap between supply and demand, the market remains undersupplied, the report finds.
In the long term, the industry needs at least to double its development pipeline of new projects by , it says. A number of projects at very advanced stages of development are waiting for an improved supply-demand market situation in order to commence uranium production," the report says. The report also considers supply and demand in the conversion, enrichment and fuel fabrication sectors.
Near-term requirements for uranium hexafluoride will be met by commercial inventories, and the ramp-up and restart of existing facilities by , but more conversion capacity will be needed in the long term. Existing enrichment capacity is sufficient to meet reactor requirements. Additional capacity might be needed in the second half of the next decade under the Reference Scenario - and in the current decade under the Upper Scenario - but the modular nature of centrifuge technology and the construction times for nuclear power reactors mean that expansion of enrichment capacity can take place in a timely way, and supply challenges are not expected, the report finds.
Groundwater from solution mining operations is circulated through a resin bed to extract and concentrate the uranium. Despite the name, the concentrated uranium product is typically a black or brown substance called yellowcake U 3 O 8. Mined uranium ore typically yields one to four pounds of U 3 O 8 per ton of ore, or 0. The solid waste material from pit and underground mining operations is called mill tailings. The processed water from solution mining is returned to the groundwater reservoir where the mining process is repeated.
The next step in the nuclear fuel cycle is to convert yellowcake into uranium hexafluoride UF 6 gas at a converter facility. Three forms isotopes of uranium occur in nature: U, U, and U Current U. The uranium hexafluoride gas produced in the converter facility is called natural UF 6 because the original concentrations of uranium isotopes are unchanged. Two types of uranium enrichment processes have been used in the United States: gaseous diffusion and gas centrifuge.
The United States currently has one operating enrichment plant, which uses a gas centrifuge process. Enriched UF 6 is sealed in canisters and allowed to cool and solidify before it is transported to a nuclear reactor fuel assembly plant by train, truck, or barge.
These laser-based enrichment processes can achieve higher initial enrichment isotope separation factors than the diffusion or centrifuge processes and can produce enriched uranium more quickly than other techniques. Once the uranium is enriched, it is ready to be converted into nuclear fuel. At a nuclear fuel fabrication facility, the UF 6 , in solid form, is heated to gaseous form, and then the UF 6 gas is chemically processed to form uranium dioxide UO 2 powder.
The powder is then compressed and formed into small ceramic fuel pellets. The pellets are stacked and sealed into long metal tubes that are about 1 centimeter in diameter to form fuel rods. The fuel rods are then bundled together to make up a fuel assembly.
Depending on the reactor type, each fuel assembly has about to fuel rods. A typical reactor core holds to fuel assemblies. Once the fuel assemblies are fabricated, trucks transport them to the reactor sites.
The fuel assemblies are stored onsite in fresh fuel storage bins until the reactor operators need them. At this stage, the uranium is only mildly radioactive, and essentially all radiation is contained within the metal tubes. Typically, reactor operators change out about one-third of the reactor core 40 to 90 fuel assemblies every 12 to 24 months. The reactor core is a cylindrical arrangement of the fuel bundles that is about 12 feet in diameter and 14 feet tall and encased in a steel pressure vessel with walls that are several inches thick.
The reactor core has essentially no moving parts except for a small number of control rods that are inserted to regulate the nuclear fission reaction. Placing the fuel assemblies next to each other and adding water initiates the nuclear reaction. After use in the reactor, fuel assemblies become highly radioactive and must be removed and stored under water at the reactor site in a spent fuel pool for several years. Even though the fission reaction has stopped, the spent fuel continues to give off heat from the decay of the radioactive elements that were created when the uranium atoms were split apart.
The water in the pool serves to both cool the fuel and block the release of radiation. From through December 31, , a total of , fuel assemblies had been discharged and stored at the sites of closed and operating commercial nuclear reactors in the United States.
Within a few years, the spent fuel cools in the pool and may be moved to a dry cask storage container at the power plant site. Many reactor operators store their older spent fuel in these special outdoor concrete or steel containers with air cooling.
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