Enrichment Facilities

The analytical requirements and specifications for UFg that is intended as the feed material for isotope enrichment facilities are summarized in an extensive series of documents published by the American Society for Testing and Materials (ASTM). A small portion of these, not a representative sample, is listed in Table 2.4. 

As mentioned earlier, ASTM is not the only source and there are several other reports and publications that deal with analytical methods for characterizing UFg and its impurities. For example, an Oak Ridge National Laboratory report on characterizing technetium and transuranic elements in depleted UFg cylinders (Hightower et al. 2000) or for transport of UFg cylinders (lAEA-TECDOC-750 1994). 

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Opportunities for Cost deduction in the Ttecontamination and Decommissioning of the Nation s Uranium Enrichment Facilities,V3.tLoaA Academy Press, Washington, D.C., 1996. 

The Canadian Deuterium Uranium reactor fissions with natural uranium, hence, no dependence on national or international fuel enrichment facilities that are needed to enrich uranium to about 3% U-235 to achieve criticality with light water moderation. 

During the conversion process, the object is to create uranium hexafluoride (UF ), a highly corro-sh e substance that is gaseous at high temperatures, but is a white crystalline solid at lower temperatures. Uranium hexafluoride is easily transported in its ciystalline form to an enrichment facility (the step taken after conversion), but the gaseous form is well suited for the enrichment process, itself. First, the... 

Environmental control in respect of determining concentrations and isotope ratios, e.g. of U, Pu and other actinides, is also required in routine measurements near to nuclear power plants, uranium enrichment facilities or nuclear waste recycling companies. Groundwater samples are analyzed after dilution directly by ICP-MS for soils a digestion step before mass spectrometric measurement is necessary. If isobaric interferences are observed a trace matrix separation and/or a careful analyte separation (e.g. of U and Pu) is recommended. 

In plutonium-fueled breeder power reactors, more plutonium is produced than is consumed (see Nuclear REACTORS, reactor types). Thus the utilization of plutonium as a nuclear energy or weapon source is especially attractive to countries that do not have uranium-enrichment facilities. The cost of a chemical reprocessing plant for plutonium production is much less than that of a uranium-235 enrichment plant (see Uraniumand URANIUM compounds). Since the end of the Cold War, the potential surplus of 239Pu metal recovered from the dismantling of nuclear weapons has presented a large risk from a security standpoint. 

The FNFCC would absorb the high-level waste program, Barnwell, and all enrichment facilities. Thus, all these items would be off-budget in the future but still approved annually by the Congress. 

Uranium with isotopic abundances different from that of natural uranium is the primary signature for HEU production activities. In any separation technology some enriched uranium will inevitably be released to the environment. Environmental samples taken at or near an enrichment facility can contain some of the enriched material altering the uranium isotopic abundance. Analysis of samples of vegetation, water and soil for uranium isotopic content using a sensitive analytical technique, such as thermal ionization mass spectrometry is recommended as the primary technique for the detection of HEU production. 

Table 12.5 shows expected isotopic uranium contents which might be expected as product from cascade type (gaseous diffusion or gas centrifuge) enrichment facilities. While the highly enriched U is actually the target of these efforts one should also be able to verify the production of low enriched uranium. Columns 5 and 6 of Table 12.5 show the isotopic enrichments which would result from a 1000-1 mixture of namral U and low or high enriched U. Table 12.6 shows the ratios of the isotopes U and U relative to the in each mixture. The 0.6% isotopic shift in the ratio in the case of LEU-MIX should be detectable by today s technology. The 0.13% in ratio... 

Uranium isotopic abundances in cascade type enrichment facility atom fractions of source materials... 

Nuclear operating costs do not include the construction and operation of the U.S. government uranium fuel enrichment facilities. When all three of these enrichment facilities were operating at full capacity, their power consumption was similar to that of the country of Australia. Other excluded operating costs include Federal regulation, long term waste disposal and any health costs that are associated with people being exposed to radiation. 

The main advantage of a heavy water reactor is that it eliminates the need for building expensive uranium enrichment facilities. However, D2O must be prepared by either fractional distillation or electrolysis of ordinary water, which can be very expensive considering the amount of water used in a nuclear reactor. In countries where hydroelectric power is abundant, the cost of producing D2O by electrolysis can be reasonably low. At present, Canada is the only nation successfully using heavy water nuclear reactors. The fact that no enriched uranium is required in a heavy water reactor allows a country to enjoy the benefits of nuclear power without undertaking work that is closely associated with weapons technology. 

AR490 3.25 Standard format and content of safety analysis reports for uranium enrichment facilities,... 

The Type-J wipers are also used to take samples in a certain enrichment facility under safeguards in a nuclear weapons state. The wiper is inserted in a special metal fitting (a so-called Koshelev fitting) that is part of the pipe-work connected to the enrichment cascade. Therefore, this sample comes into contact with the UFe gas in the pipe-work and can be used to detect the presence of material with higher enrichment than declared. 

This means we must examine fuel cycles that use different processing, different separation systems for isotopes, and also place different and smaller demands on enrichment facilities. 

Many of the secondary sources of uranium described above also displace demand for UFg conversion. These include inventories of UFgand low enriched uranium (LEU), Russian and US ex-military HEU and plutonium, uranium and plutonium recovered by civil spent fuel reprocessing, and UFg supply from the re-enrichment of tails. In addition, underfeeding of enrichment facilities can also affect the UFg market. 

The URENCO USA facility began operations on June 11, 2010. Construction of the project will continue until the plant reaches the planned 5700 tSW/a capacity. URENCO USA is the first enrichment facility to be built in the United States in 30 years and the first ever using centrifuge enrichment technology. At the end of December 2014, capacity at... 

The fuel fabrication process is shown schematically in Figure 12.4 from conversion of enriched uranium hexaflouride (UFg) gas to the final assembled product. The enriched material is received from an enrichment facility in the form of UFg. Figure 12.5 shows the original gaseous diffusion plant in Oak Ridge, Tennessee. This facility is no longer in... 

Natural (NU or Unat), depleted (DU), low-enriched (LEU), and high-enriched (HEU) uranium the content of the only natural fissile isotope, U—is an important feature of uranium applications and value. In natural uranium, the content of this isotope is 0.720 atom % or 0.711 wt% (Table 1.2). LEU is defined as U content between 0.720% and just below 20%, while HEU encompasses uranium with U content above 20%. The 20% borderline between LEU and HEU is artificial and was based on the assumption that nuclear weapons with 20% or less U would not be efficient. The waste, or tails, of the isotope enrichment process contains less U than in natural uranium and is defined as depleted uranium (DU). The U-235 content in DU is usually in the range of 0.2%-0.4%. DU is used mainly in armor piecing ammunition, in reactive armor of tanks, in radiation shielding, and is also used as ballast weights in aircraft. In addition, many of the commercially available fine chemicals of uranium compounds are based on the tails of uranium-enrichment facilities and usually labeled as not of natural isotope composition. 

An alternative method for production of UFg (the fluoride volatility process) for enrichment facilities from uranium ore concentrates was developed by Honeywell and is practiced at its Metropolis plant. Figure 1.11 schanaticaUy compares this process with the classic process described earlier. 

Some Examples of the ASTM Methods Concerning Characterization of UF for Enrichment Facilities... 

The rigorons specifications for nuclear grade materials that are used as nuclear fuel (mainly UO2 and U metal or alloys) or as feed material for enrichment facilities (primarily UFg) are described in great detail and require strict control. The focus of the analytical procedures is on impurities that affect the nuclear properties (mainly through absorption of neutrons), chemical properties (Uke corrosion resistance or those that may concentrate in the enrichment product), and physical and mechanical properties (like pellet strength, heat transfer). The isotopic composition of uranium plays an important role as the value of uranium strongly depends on the content. 

Nuclear forensics also plays a role with regard to the processing of uranium ore concentrates in the UCF and fabrication of uraninm oxide for fueling nuclear reactors or of uranium hexafluoride for isotope enrichment facilities. Characterization of the nuclear materials can detect unauthorized operations and partially ascertain that no undeclared activities are taking place but one shonld always bear in mind that absence of evidence is not evidence of absence. In some cases, relevant information may be obtained from bulk samples but highly significant details may be found in analysis of single particles. Some examples will be presented here, but more details are discussed in Section 5.4. 

For safeguards purposes, swipe samples are collected from different surfaces inside the enrichment facility. These could include operational equipment like pipes, cylinders, and machinery or even surfaces from the walls and floor. Bulk isotopic analysis of these swipe samples would give the average enrichment of the released particles. However, for a complete understanding of the operations carried out in the facility, single particle analysis is more revealing, as discussed and demonstrated here. 

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