Uranium enrichment process

Uranium carbonates, 25 430-432 Uranium chlorides, 25 438-439 Uranium compounds, 25 421-434 handling, 17 529 Uranium dioxide, 25 422-423 Uranium-enrichment process gas centrifuge, 25 413-415 Uranium exploration, 25 398 URanium Extraction (UREX) process, 25 420... 

UF6 ( hex ) is the only readily available uranium compound that is volatile at room temperature. It is a colorless solid that is used in the uranium enrichment process. It sublimes at room temperature without melting. UF6 is rapidly hydrolyzed by water and is a fluorinating agent. This latter property means that one must carefully choose the materials to contain UF6. 

The nuclear area is one that has been heavily dependent upon isotope ratio mass spectrometry performed by thermal ionization. Applications in this area are among the major reasons for the continued push to analyze smaller and smaller samples. There are two primary reasons for this (1) maximum practicable reduction of the hazards associated with radioactivity and (2) presence of often only a very small amount of the target element available. Areas addressed include evaluation of uranium enrichment processes [86], isotopic analysis of transuranium elements (all elements through einsteinium have been analyzed) [87], and environmental monitoring for release of uranium and other actinides [88,89]. This last area has received renewed emphasis in the wake of the Gulf War [90]. 

A very dangerous fire hazard in the form of a solid or dust when exposed to heat or flame. It can react violently with air, CI2, F2, HNO3, NO, Se, S, water, NH3, BrFs, trichloroethylene, nitryl fluoride. During storage it may form a pyrophoric surface due to effects of air and moisture. Depleted uranium (the by-product of the uranium enrichment process, with relatively low radioactivity) is used in armor-piercing shells, ship or aircraft ballast, and counterbalances. Uranium is also used in making colored ceramic glazes. 

Phosgene is sometimes a byproduct of manufacturing aniline dyes, polycarbonate resins, coal tar, pesticides, isocyanates, polyurethane, and pharmaceuticals. Phosgene also occurs in uranium enrichment processes and bleaching sand for glass production. 

During the period from 1943 to 1947 in the United States, the Manhattan Project carried four uranium enrichment processes through the large pilot stage and into production to the extent noted below. 

CHEMEX French uranium enrichment process based on solvent extraction... 

While other materials have been used as feed to uranium-enrichment processes, the most widely used volatile compound of uranium is the hexafluoride. At room temperature, UFe is a colorless solid with a density of 5.1 g/cm. It sublimes at atmospheric pressure, and at room temperature has a vapor pressure of 100 torr. The main disadvantage of working with UFe is its high chemical reactivity. It reacts vigorously with water, but is not very reactive with dry air. UF5 reacts with most metals however, nickel, copper, and aluminum are resistant. This holds only for pure UFg the presence of even small amounts of HF increases the rate of attack on even the resistant metals. 

Teflon, discovered in 1938, does not burn. It does not melt below 620 degrees Fahrenheit but rather turns into a translucent gel. It does not conduct electricity at aU, does not combine with oxygen, does not dissolve, is unaffected by acids, and is immune to molds, fungi, and bacteria. It was deemed completely useless until it was found to be the only material in existence that could enable the uranium enrichment process used in the Manhattan Project. When finally made available for public use, it was as nothing more exotic than a nonstick coating for cookware and steam irons. 

The nuclear industry, both for production of weapons and for nuclear reactors, is stiU a major consumer of fluorine compounds. In the USA annually about 5000 tonnes of fluorine are produced. Of this quantity, about 80% is used to produce uranium hexafluoride for the uranium enrichment process [50.4]. 

Many studies discussed the timing for the deployment of the commercial SFR and the transition strategies from LWRs to SFRs (Walter et al., 2012 CEA, 2012a). LWRs have already converted (and will convert) some to plutonium in their operation. There already exists enough as depleted uranium from the uranium enrichment process. Therefore the introduction of SFRs seems consistent with the current LWR system in terms of the nuclear material supply. The breeding ratio necessary for SFRs is estimated as 1.0—1.2 and more depending on the deployment scenarios. 

Depicted uranium is used extensiveiy in pyrotechnics which have armor piercing capabiiities. Depicted uranium deficient in the more radioactive isotope U235, is the waste product of the uranium enrichment process. The depicted uranium is formed into projectiles that can penetrate armor because of their high density and mechanical properties. The impact of the projectile causes the uranium to form many pyrophoric fragments which can ignite fuel and munition items. 

The only current industrial application of centrifugal separation of gases known to the author is the separation of uranium isotopes. Natural uranium is about 0.7% balance The uranium enrichment process increases the content to about 2 to 3% for electric power reactors and to about 90% for nuclear weapons, (There are several types of uranium enrichment processes [1], of which only the centrifuge process is discussed here.) All enrichment processes currently in use convert the uranium to uranium hexafluoride, UFg, which sublimes to a gas (as does solid carbon dioxide, dry ice ) at one atmosphere and 56.5°C. The resulting gas is 0.7 mol% (M = 349 g/mol) and... 

TAILINGS. In the nuclear context, the depleted stream remaining from a uranium enrichment process or from uranium milling. In relative terms, the tailings (also occasionally referred to as tails ) are depleted uranium reduced in uranium-235, while the enrichment process is enriched in that Isotope. In general, tailings make poor sources for development of nuclear weapons or for use in radlolt ical dispersal devices (RDD) because they are low in radioactive uranium-235. 

De-enrichment of HEU from approximately 93% to 3% can be accompHshed using the depleted tails from the original enrichment process. These tails contain on the average 0.20% U. The de-enrichment of 11 of HEU uses 32 t of tads, yielding approximately 33 t of fuel having an enrichment of 3% U. Producing the same amount of 3% enriched uranium from natural sources would requite approximately 180 t of natural uranium metal. Therefore, 1 t of HEU is equivalent to 180 t of natural uranium. 

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... 

Another, more modern, route of processing the yellow cake is shown in Figure 5.38, accomplishes the production of enriched uranium oxide entirely by pyroprocessing. Thus, uranium is finally obtained in three forms metallic uranium, enriched uranium dioxide, and natural uranium dioxide. As the flowsheet shows, and as briefly described herein, these are essentially the products of hydro and pyro-based processing schemes. 

Enrichment, Isotopic—An isotopic separation process by which the relative abundances of the isotopes of a given element are altered, thus producing a form of the element that has been enriched in one or more isotopes and depleted in others. In uranium enrichment, the percentage of uranium-235 in natural uranium can be increased from 0.7% to >90% in a gaseous diffusion process based on the different thermal velocities of the constituents of natural uranium (234U, 235U, 238U) in the molecular form UF6. 

Fig. 8.4 Ideal cascade for uranium enrichment. The height of each section is roughly proportional to the number of stages in that section and the width at any stage to the amount of material being processed in that stage (Modified from Spindel in Rock, P. A., ACS Symposium Series 11. Isotopes and Chemical Principles 1975)...

In any uranium separation process the work of enrichment increases rapidly with 235U content in the product. Because the price of natural uranium varies widely with time and location (and fluctuating government subsidies) it is useful to distinguish between the price of the feed and the value added by the separative process. For example, the purchaser himself might provide the feed and then pay only for the separative work required to make the desired product. Separative work is defined in Equation 8.7. 

After the oil crisis in 1973, the need for large enrichment capacities for supply of fuel to the nuclear power plants became obvious and several European countries (Belgium, France, Italy and Spain) decided to build the huge Eurodif gas diffusion plant. This plant is located in France, in the Rhone valley, a few kilometers away from the Pierrelatte plant. Simultaneously, England, West Germany and the Netherlands (the Troika) chose to jointly develop the centrifugation process for uranium enrichment, which does not use membranes. 

The rate and quantity of radon and uranium contributed to waters exposed to mineralized outcrops and the subsequent mobility of these elements in the present day environment has not been previously documented. This paper presents the results from leaching experiments carried out on uranium-enriched Horton Group sandstones in the Windsor area of Nova Scotia. Understanding of these processes is important both to environmental and exploration geochemistry. 

Uranium is best known as a fuel for nuclear power plants. To prepare this fuel, uranium ores are processed to extract and enrich the uranium. The process begins by mining uranium-rich ores and then crushing the rock. The ore is mixed with water and thickened to form a slurry. The slurry is treated with sulfuric acid and the product reacted with amines in a series of reactions to give ammonium diuranate, (NH4)2U20 . Ammonium diuranate is heated to yield an enriched uranium oxide solid known as yellow cake. Yellow cake contains from 70—90% U3Og in the form of a mixture of U02 and U03. The yellow cake is then shipped to a conversion plant where it can be enriched. 

As is well known, ammunition containing depleted uranium (DU) was used by NATO, for example, in the former Yugoslavia. To evaluate the origin of DU (enrichment process of natural uranium or reprocessing of exhausted nuclear fuel) it is necessary to directly detect the presence... 

---