Uranium estimation

Extraction. For amounts of uranium estimated to be under about 1400 y, plpet 5 ml of O.IH trl-n-octylphosphlne oxide In cyclohexane Into the extraction vessel containing the treated... 

Its importance depends on the nuclear property of being readily fissionable with neutrons and its availability in quantity. The world s nuclear-power reactors are now producing about 20,000 kg of plutonium/yr. By 1982 it was estimated that about 300,000 kg had accumulated. The various nuclear applications of plutonium are well known. 238Pu has been used in the Apollo lunar missions to power seismic and other equipment on the lunar surface. As with neptunium and uranium, plutonium metal can be prepared by reduction of the trifluoride with alkaline-earth metals. 

Manufacturers. Besides manufacturers in the United States, commercial fluorine plants are operating in Canada, France, Germany, Italy, Japan, and the United Kingdom (see Table 5). Fluorine is also produced in the Commonwealth of Independent States (former Soviet Union) however, details regarding its manufacture, production volumes, etc, are regarded as secret information. The total commercial production capacity of fluorine in the United States and Canada is estimated at over 5000 t/yr, of which 70—80% is devoted to uranium hexafluoride production. Most of the gas is used in captive uranium-processing operations. 

The U.S. Department of Energy (DOE) and the NEA/IAEA employ similar terms to classify uranium resources, as (7) reasonably assured, estimated additional (EA), or speculative. The NEA/IAEA divides the estimated additional resources into two types, EAR-I and EAR-II, describing known resources and undiscovered ones, respectively (8). 

Domestic. Estimates of U.S. uranium resources for reasonably assured resources, estimated additional resources, and speculative resources at costs of 80, 130, and 260/kg of uranium are given in Table 1 (18). These estimates include only conventional uranium resources, which principally include sandstone deposits of the Colorado Plateaus, the Wyoming basins, and the Gulf Coastal Plain of Texas. Marine phosphorite deposits in central Elorida, the western United States, and other areas contain low grade uranium having 30—150 ppm U that can be recovered as a by-product from wet-process phosphoric acid. Because of relatively low uranium prices, on the order of 20.67/kg U (19), in situ leach and by-product plants accounted for 76% of total uranium production in 1992 (20). 

Foreign. The OECD/NEA and IAEA have issued annual reports on world uranium resources, production, and demand since the mid-1960s (2—6). NEA/IAEA data for reasonably assured and estimated additional resources at costs of 80 and 130/kg uranium are given in Table 2 (21). These estimates incorporate data from both former world outside centrally planned economies (WOCA) and non-WOCA nations. A summary of other known uranium resources with and without cost range estimates is provided in Table 3 (22). These resources total about 1.4 x 10 t and include estimates that are not strictly consistent with standard NEA/IAEA definitions. 

Estimates of speculative lesouices (SR) at 130/kg uianium and those having an unassigned cost range are provided ia Table 4 (23). These resources, which total about 11.28 x 10 t, would be ia addition to the reasonably assured and estimated additional resources. Estimates of uranium resources from unconventional and by-product sources are presented ia Table 5 (24). These resources total about 7 x 10 t for phosphates, 0.013 x 10 t for nonferrous ores, 0.016 x 10 t for carbonates, and 0.014 x 10 t for lignites. These would be ia addition to the reasonably assured resources, estimated additional resources, and the speculative resources (24). 

World annual uranium requirements in 1993 were estimated at about 58,382 t natural uranium equivalent. Reactor-related requirements are expected to rise about 1015 t/yr on the average, reaching 75,700 t U total requirements in the year 2010. The cumulative aggregate world uranium requirements for the period 1993—2010 are estimated to be about 1.185 X 10 t U metal (29). 

HEU De-Enrichment. Highly enriched uranium (HEU), initially enriched to >93% U, for use in research, naval reactors, and nuclear weapons, may be de-enriched and fabricated into fuel for civihan nuclear reactors. An estimate of the world inventory of highly enriched uranium in the nuclear weapons states is provided in Table 6 (34). 

Resource estimates are divided into separate categories reflecting different levels of confidence in the quantities reported, and further separated into categories based on the cost of production. A listing of uranium resources by country is given in Table 3. 

If uranium is internally cycled in coastal environments or if the riverine delivery of U shows some variability, residence time estimates (regardless of their precision) cannot be sensitive indicators of oceanic uranium reactivity. Based on very precise measurements of dissolved uranium in the open ocean, Chen et alJ concluded that uranium may be somewhat more reactive in marine environments than previously inferred. Furthermore, recent studies in high-energy coastal environments " indicate that uranium may be actively cycled and repartitioned (non-conservative) from one phase to the next. 

It is estimated that the earth s age is in the neighborhood of 4 to 7 billion years. These estimates are basically derived from carbon-14, potassium-40, uranium-235, and uranium-238 dating of earth rocks and meteorites. The meteorites give important data as to the age of our solar system. Geologic time is felt to be represented by the presence of rock intervals in the geologic column (layers of rock formations in vertical depth) or by the absence of equivalent rocks in correlative columns in adjacent locations [25,26]. The two basic factors that are used to determine geologic time are ... 

What have we learned in this estimate Surely we can say the age of the earth cannot be shorter than 5 X 10s years. That was when the uranium mineral clock was wound—but the clock could be much older. To evaluate this number further, we must look for other types of data. 

The chemistry of plutonium is unique in the periodic table. This theme is exemplified throughout much of the research work that is described in this volume. Many of the properties of plutonium cannot be estimated accurately based on experiments with lighter elements, such as uranium and neptunium. Because massive amounts of plutonium have been and are being produced throughout the world, the need to define precisely its chemical and physical properties and to predict its chemical behavior under widely varying conditions will persist. In addition to these needs, there is an intrinsic fundamental interest in an element with so many unusual properties and with so many different oxidation states, each with its own chemistry. 

The process we have followed Is Identical with the one we used previously for the uranium/oxygen (U/0) system (1-2) and Is summarized by the procedure that Is shown In Figure 1. Thermodynamic functions for the gas-phase molecules were obtained previously (3) from experimental spectroscopic data and estimates of molecular parameters. The functions for the condensed phase have been calculated from an assessment of the available data, Including the heat capacity as a function of temperature (4). The oxygen potential Is found from extension Into the liquid phase of a model that was derived for the solid phase. Thus, we have all the Information needed to apply the procedure outlined In Figure 1. 

In 1938, Lise Meitner, Otto Hahn, and Fritz Strassmann realized that, by bombarding heavy atoms such as uranium with neutrons, they could split the atoms into smaller fragments in fission reactions, releasing huge amounts of energy. We can estimate the energy that would be released by using Einstein s equation, as we did in Example 17.5. 

The force constants of the Ni—P bond in P " nickel carbonyl complexes increase in the order MeaP < PHg < P(OMe)a < PFs. This order is different from that of the donor-acceptor character, as estimated from uco-The lengthening of the P—O bond of triphenylphosphine oxide upon complexation with uranium oxide has been estimated by i.r. spectroscopy. However, A -ray diffraction shows little difference in the P-O bond lengths (see Section 7). Some SCF-MO calculations on the donor-acceptor properties of McaPO and H3PO have been reported. 

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