Uranium feed materials

Constraints of Plant Design. The potential hazards encountered in the uranium feed materials processing industry include many that are common to the heavy chemicals industry. However special problems present themselves owing to direct radiation, the possibility of inhalation and ingestion of radioactive dusts and gases, nuclear safety, and more unusual chemical hazards. 

The total cost of a typical fuel assembly that contains about 450 kg (about 1000 pounds) of uranium (in the form of the oxide) is as follows. To obtain the 450 kg of 4.5% U-235 fuel requires 3721 kg of natural uranium feed material (about 9652 pounds U3O8 = 8186 pounds of uranium) for approximately 410,000 at 50/pound, and utilized 3424 SWU, 480,000 at 140/SWU. The conversion to the hexafluoride and back to the oxide probably accounted... 

The cost of enriched material from a gaseous diffusion plant depends both on the cost of separative work and of feed material. It can be seen from equation 15 that if the optimum tails concentration from a gaseous diffusion plant is 0.25%, the ratio of the cost of a kg of normal uranium to the cost of a kg of separative work equal to 0.80 is impfled. Because the cost of separative work in new gaseous diffusion plants is expected to be about 100/SWU, equation 16 gives the cost per kg of uranium containing 4% as about 1,240. 

At various facilities that process uranium for defense programs, uranium is released to the atmosphere under controlled conditions, resulting in deposition on the soil and surface waters. Monitoring data from the area surrounding the Fernald Environmental Management Project (formerly the Fernald Feed Materials Production Center) showed that soil contained uranium released from the facility (Stevenson and Hardy 1993). 

Stevenson KA, Hardy EP. 1993. Estimate of excess uranium in surface soil surrounding the feed materials production center using a requalified data base. Health Phys 65(3) 283-287. 

UCI4, which boils without decomposition at 791°C, was used as feed material for the Y-12 electromagnetic uranium enrichment plant. It is hygroscopic and hydrolyzes in moist air. 

The present process still depends on the production of UF4 as a pure intermediate which may be reduced to metal for fueling the Magnox reactors or further fluorinated with fluorine gas to produce UFg, the essential feed material for all of the uranium isotopic-enriching processes. 

In late summer 1943 it was decided that K-25 would play a lesser role than ori ally intended. Instead of producing fully enriched uranium-235, the gaseous diffusion plant would now provide around fifty percent enrichment for use as feed material in Y-12. This would be accomplished by eliminating the more troublesome upper part of the cascade. Even this level of enrichment was not assured since a barrier for the diffusion plant still did not exist. The dedsion to downgrade K-25 was part of the... 

Stripping stages are used, which constitute an adequate excess to deal with the various types of feed material. The uranium equilibrium lines are in fact... 

Since a single furnace is used for three dryway operations, calcination, hydrogen reduction and hydrofluorination, the transfer of solids is minimized. The initial charging of trays and loading these into the furnace is relatively free from dust hazard since the ammonium di-uranate feed material is damp. Special precautions are needed, however, for removal of the final uranium tetrafluoride product from the trays, since it is a dry dusty powder and tends to adhere to the trays to some extent. This operation is therefore carried out in a small glove box , i.e. in a sealed and vented... 

A residence time of 4-8 hr in the reactor leaves only about 1 to 2 per cent of the uranium dioxide unconverted. A temperature gradient in the top, middle and lower beds of 400°C, 500 C, and 600°C respectively gives the best results. The overall excess of hydrogen fluoride is of the order of 100 per cent, and this is recovered as a concentrated solution. The tetrafluoride product has a packing density of about 3-6 from dioxide feed material having a packing density of 4-4. 

Nuclear forensic principles apply to all three of the special nuclear materials, including uranium of any enrichment (or depletion) in They can also be applied to other materials arising in the nuclear fuel cycle (e.g., Np, Am) and to the natural-composition feed materials (uranium and thorium). 

Typically, the input flow of UFs is adjusted so that roughly half of the feed diffuses through the walls of the barrier tubes into interstitial space, becoming enriched (product), while the rest remains in the tubes, becoming depleted (tails). To obtain significant enrichments, this process must be repeated multiple times (Krass et al. 1983). In a cascade of diffusion cells, the product of one enrichment cell is used as feedstock for another. The cascade is simple if the tails are discarded the cascade is countercurrent if the tails are reintroduced as feed in a lower emichment stage. Simple cascades are not used because of the potentially profligate waste of uranium. After the initial start up of a countercurrent cascade, feed material is introduced only in the amount necessary to balance the withdrawal of product and tails. 

Denaturing the feed with indicated that a uranium feed composition of 20 1 ( "U U) results in only a doubling of the critical inventory for singlecell concepts. However, the total uranium inventory is 40 times greater than for the pure core, thus making the practicality of diversion of this U/ U for weapons purposes most unlikely. The significant feature of a gas core concept from a proliferation standpoint lies in the relatively low amount of fissile material in the system (core plus blanket) at any time. 

In Chapter 2, we take a more detailed look at the analytical chemistry pertaining to key commercial activities, that is, uranium mining and its utilization in the nuclear fuel cycle (NFC) first, in the milling process, uranium-containing deposits are processed to form uranium ore concentrates (UOC) that are then shipped to uranium conversion facilities (UCF), where the uranium is transformed into high-purity nuclear grade compounds. These can serve as fuel for nuclear power plants or as feed material for isotope enrichment. Then we discuss the analytical aspects of compliance with the strict specifications of the materials used in enrichment plants and in fuel fabrication facilities. Finally, we deal with the analytical procedures to characterize irradiated fuel and waste disposal of spent fuel. 

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