How Easy is It to Acquire Depleted Uranium
Frequently Asked Questions about Depleted Uranium Deconversion Facilities
Deconversion involves extracting the fluoride from the depleted uranium hexafluoride (DUF6), or "tailings," produced during the uranium enrichment process. The questions and answers on this page provide information about deconverting DUF6 into fluoride products (for commercial resale) and uranium oxides (for disposal).
On this page:
- What role does depleted uranium play in the nuclear fuel cycle?
- What is the current method for disposing of depleted uranium?
- Does the radioactivity of depleted uranium increase over time?
- What are the principal hazards at a depleted uranium deconversion facility?
- What will happen to the waste products from the deconversion process?
- What projects are currently planned for depleted uranium deconversion in the United States?
- What is the NRC's role in the construction and operation of the deconversion plant?
- What will happen in the NRC's licensing process?
- How does this project relate to the National Enrichment Facility, located in Lea County, New Mexico?
- Where is the nearest office that will inspect this plant for safety?
Index to All Frequently Asked Questions Pages
What role does depleted uranium play in the nuclear fuel cycle?
Depleted uranium is produced in the uranium enrichment process when uranium-235 (U235) is extracted from natural uranium to concentrate this isotope into fuel for nuclear reactors.
For the types of nuclear power plants operating in the United States, uranium needs to be enriched. Natural uranium primarily contains two isotopes, uranium-238 (U238) (99.3 percent) and U235 (0.7 percent). The concentration of U235, the readily fissionable isotope in uranium, needs to be increased to between 3 and 5 percent for practical use as a nuclear fuel. Enrichment plants use various means to concentrate the U235, including gaseous diffusion, gas centrifuge, or laser separation enrichment.
The U235 is increased in a portion of material by decreasing the U235 in the remainder of the material. For example, if an enrichment facility processes 1,000 kilograms (kg) of natural uranium to raise the U235 concentration from 0.7 percent to 5 percent, the facility would produce 85 kg of enriched uranium and 915 kg of depleted uranium. The amount of U235 in the bulk of the material decreases, or is depleted, to a concentration of 0.3 percent. Uranium with a concentration of U235 below that of natural uranium (0.7 percent) is called depleted uranium.
What is the current method for disposing of depleted uranium?
Depleted uranium is primarily stored at the enrichment facilities in the form of uranium hexafluoride (UF6), a chemical form required for enrichment but not optimal for long-term storage. This depleted uranium hexafluoride (DUF6) is typically stored in 14-ton cylinders near the enrichment facilities. Processed depleted uranium may be sold for commercial uses such as counterweights, military penetrators, shielding, etc. Alternatively, material may be transferred to the U.S. Department of Energy (DOE) for a fee. It may also be disposed of at commercial disposal sites if the material meets the site's disposal criteria.
Depleted uranium can be disposed of as low-level radioactive waste if it is converted to chemically stable uranium oxide compounds, such as triuranium octoxide (U3O8) or uranium dioxide (UO2), which are similar to the chemical form of natural uranium.
DOE currently has more than 700,000 metric tons (771,000 U.S. tons) of depleted UF6 in storage. Under the U.S. Enrichment Corporation (USEC) Privatization Act, DOE is required to accept depleted uranium from a uranium enrichment facility licensed by the U.S. Nuclear Regulatory Commission (NRC) if the depleted uranium is determined to be low-level radioactive waste. Under the USEC Privatization Act, the licensee must reimburse DOE for its costs.
Does the radioactivity of depleted uranium increase over time?
Yes and no. Uranium is a radioactive material with two primary isotopes, U235 and U238. These isotopes decay at a constant rate that has a half-life (i.e., time for the activity to reduce by half) greater than 100 million years. No significant change would be observed in the radiation emitted from these isotopes during a typical 75-year lifetime. However, the buildup of daughter products from the decay of these isotopes does increase the total radiation emitted from the material.
In the radioactive decay process, an atom transforms by emitting radiation in the form of particles or energy. Uranium undergoes radioactive decay very slowly. The half-life for U238 is 4.5 billion years. After one half-life, a container that originally held 10,000 kg of pure U238 would be reduced to 5,000 kg of U238, along with approximately 5,000 kg of associated daughter products. Many of these daughter products are also unstable and undergo further radioactive decay until they transform into a stable isotope of lead. As the U238 decays, the amount of daughter products increases which, in turn, increases the total radiation emitted from a container of U238. The radioactivity of the daughter products continues to increase until it reaches equilibrium with the activity of the parent nuclide (i.e., U238 or U235).
For illustrative purposes only, consider a storage cylinder of depleted uranium oxide which contains 10,000 kg of solid uranium dioxide. In the first year, the radioactivity at 1 meter from the cylinder would be approximately 0.26 mrem/hr (0.0026 mSv/hr). Standing in this position for approximately 37 hours would cause a person to receive the equivalent of one chest X-ray, 10 mrem (0.1 mSv). After 10,000 years, this radioactivity would rise to approximately 1.0 mrem/hr (0.01 mSv/hr), and a person standing in this position for 10 hours would receive the equivalent of one chest X-ray. After about 1 million years, the radioactivity would reach equilibrium at approximately 30 mrem/hr (0.30 mSv/hr), at a 1-meter distance. This radioactivity would result in the equivalent of one chest X-ray in approximately 20 minutes. [Note: The figures above were calculated using MicroShield v5.5, Grove Software, Inc. A cylinder with a 1.6-cm iron (7.8 g/cm3) shell was assumed to contain 10,000 kg of solid uranium dioxide (11 g/cm3). The radioactive isotopic content was projected to contain 99.7% U238, 0.3% U235, and 0.17kg of U234, and buildup due to air was included.]
What are the principal hazards at a depleted uranium deconversion facility?
Chemical exposure presents the dominant hazard at this type of facility. Uranium and fluoride compounds such as hydrogen fluoride (HF) are toxic at low chemical exposure levels.
When depleted UF6 contacts moisture in air, it reacts to form HF and uranyl fluoride gas. Uranium is a heavy metal that can be toxic to the kidneys when taken internally. HF is a corrosive acid that can be very dangerous if inhaled; it represents the principal hazard at this facility. These hazards are controlled by plant design and administrative controls to reduce the likelihood and consequences of an accidental release of these compounds. Such measures include sealed vaults, water suppression systems, controlled ventilation system, and air scrubbers. The U.S. Department of Transportation and the NRC regulate the transportation of depleted UF6 to and from the facility.
What will happen to the waste products from the deconversion process?
Deconversion permits the recovery of fluoride compounds which have commercial value when processed and purified. Depleted uranium also has some commercial value as counterweights, shielding, military penetrators, etc. In the oxide form, uranium can be disposed of as low-level radioactive waste at an approved disposal facility.
Approximately 350,000 tons of anhydrous HF are used annually in the United States.1 HF is used in the production of refrigerants, herbicides, pharmaceuticals, high-octane gasoline, aluminum, plastics, electrical components, and fluorescent light bulbs. Demand for HF for fluorocarbons, broadly used as refrigerants, is increasing as an alternative to ozone-depleting chlorofluorocarbons. Silicon tetrafluoride is used on a limited basis in microelectronics. Boron tetrafluoride is used for doping silicon chips and other purposes in the chemical industry.
As the fluorine is extracted, the uranium is converted to an oxide (either U3O8 or UO2). These oxides are chemically stable compared to UF6. They are generally suitable for near-surface disposal as low-level radioactive waste. Uranium exists in the oxide form in nature, but at significantly diluted concentrations. The specific radioactivity (radioactivity per mass of uranium oxide) of the depleted uranium oxides is less than natural uranium because of the reduction of U234, U235, and the majority of daughter products which are removed during the enrichment process. The majority of these daughter products return to natural levels over the course of several million years.
What projects are currently planned for depleted uranium deconversion in the United States?
Currently, the United States has one operating deconversion facility, which is regulated by the State of Tennessee under an Agreement State license in accordance with Title 10, Part 40, of the Code of Federal Regulations (10 CFR Part 40), "Domestic Licensing of Source Material." At this facility in Jonesborough, Tennessee, Aerojet Ordnance Tennessee, Inc., fabricates uranium metal for the U.S. Army to use as antitank rounds. This fabrication involves deconverting depleted UF4 using a process that does not produce significant quantities of fluorine or hydrogen fluoride as reaction products.
As directed by Congress, the U.S. Department of Energy (DOE) is constructing two depleted uranium deconversion facilities next to the existing gaseous diffusion uranium enrichment plants (GDP) in Paducah, Kentucky, and the Portsmouth GDP (near in Piketon, Ohio). The plants are projected to be completed in mid-year 2010.2 Together, these plants will deconvert more than 700,000 metric tons (771,000 U.S. tons) of depleted UF6 in storage in the DOE inventory. This inventory is projected to require 15–20 years to deconvert once the facilities become operational. DOE plans to dispose of the 551,000 metric tons of depleted uranium oxide as low-level radioactive waste at an estimated cost of about $428 million. See Depleted UF6 Management for additional detail regarding the DOE program.
In addition, on December 30, 2009, International Isotopes Fluorine Products, Inc. (IIFP, a subsidiary of International Isotopes, Inc.) submitted an application to the U.S. Nuclear Regulatory Commission (NRC), seeking a license to construct and operate a Fluorine Extraction Process and Depleted Uranium Deconversion (FEP/DUP) Plant near Hobbs, New Mexico. If approved, the FEP/DUP Plant will be the first major commercial deconversion facility licensed by the NRC to convert depleted UF6 to a uranium oxide for the purpose of recovering the fluoride products. The NRC's licensing safety review and development of the environmental impact statement are scheduled to be completed in 2012. This schedule may change based on the quality of the applicant's license application, its responsiveness to requests for additional information, and unanticipated higher-priority operational safety work.
What is the NRC's role in the construction and operation of the deconversion plant?
Under the Atomic Energy Act (AEA) of 1954, as amended, the NRC licenses source material (e.g., natural and depleted uranium) under Title 10, Part 40, of the Code of Federal Regulations (10 CFR Part 40), among other regulations.
The NRC implements the National Environmental Policy Act (NEPA) in accordance with its own regulations in 10 CFR Part 51, "Environmental Protection Regulations for Domestic Licensing and Related Regulatory Functions." The environmental assessment (EA) or environmental impact statement (EIS) describes the potential environmental impacts of construction, operation, and decommissioning of the new facility.
What will happen in the NRC's licensing process?
During the NRC's licensing process, the staff will conduct a thorough review of the application to ensure that it meets the technical, environmental, and security requirements under Federal law. There will be opportunities for stakeholder interaction at numerous steps throughout the process.
On receipt of a license application and environmental report, the NRC staff conducts an acceptance review of the application to ensure that it contains sufficient information to begin a review. The NRC staff also conducts a review of the application to ensure that sensitive information is identified and removed before making it publicly available. If the application is acceptable, the NRC formally dockets the submittal and makes nonclassified and nonsensitive portions publicly available in the Agencywide Documents Access and Management System (ADAMS) and on the NRC's public Web site (see IIFP Fluorine Extraction Process and Depleted Uranium Deconversion (FEP/DUP) Plant Licensing). Once the documents have been accepted for formal review, the NRC staff initiates the formal technical review and the environmental review. Shortly after accepting the application, the NRC also issues a Federal Register notice of opportunity to request a hearing. The term "hearing" refers to a formal judicial process before a panel of administrative law judges set up to address NRC licensing issues.
As part of a major EA or EIS, the NRC staff conducts a scoping meeting near the proposed site. This meeting affords the public an opportunity to suggest areas to be addressed in the environmental review. After the scoping process, the NRC prepares a "finding of no significant impact" for the EA or a draft EIS and offers a formal opportunity to comment on the draft. Again, the NRC staff meets with the public to accept comments on the draft EIS. Written comments are also accepted. The EIS process takes approximately 24 months.
The technical review of a new fuel cycle facility takes approximately 18–20 months to complete and determines whether the proposed project meets the NRC's safety and security requirements. The staff documents the technical review in a safety evaluation report (SER). The environmental review runs at the same time as the technical review. If a hearing is granted, the hearing process begins after issuance of the SER and EIS.
How does this project relate to the National Enrichment Facility, located in Lea County, New Mexico?
The IIFP Fluorine Extraction Process and Depleted Uranium Deconversion (FEP/DUP) Plant will be designed to process up to 22 million pounds of commercially generated depleted UF6 annually. Neither International Isotopes, Inc. (INIS), nor its subsidiary, International Isotopes Fluorine Products (IIFP), Inc., is associated with the National Enrichment Facility. INIS plans to develop independent agreements with commercial enrichment facilities to process the depleted UF6. One of these facilities may be the National Enrichment Facility, located in Lea County, New Mexico
Where is the nearest office that will inspect this plant for safety?
The NRC's Region II Office in Atlanta, GA, will conduct routine inspections of the proposed facility because it is responsible for nuclear fuel cycle facilities. Headquarters staff from Rockville, Maryland, will also perform inspections. The nearest NRC office is the Region IV Office in Arlington, Texas.
1"Toxicological Profile for Fluorides, Hydrogen Fluoride, and Fluorine," U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, September 2003.
Page Last Reviewed/Updated Monday, March 23, 2015
Source: https://www.nrc.gov/materials/fuel-cycle-fac/ur-deconversion/faq-depleted-ur-decon.html
Belum ada Komentar untuk "How Easy is It to Acquire Depleted Uranium"
Posting Komentar