Plutonium properties

Moreover physics concerning plutonium and its alloys involves predicting its properties under long-term aging in both weapons and storage environnement. The knowledge of all plutonium properties is a major challenge and first-principles studies of pure plutonium, alloys, and finite temperature simulations are needed. 

Initially, the only means of obtaining elements higher than uranium was by a-particle bombardment of uranium in the cyclotron, and it was by this means that the first, exceedingly minute amounts of neptunium and plutonium were obtained. The separation of these elements from other products and from uranium was difficult methods were devised involving co-precipitation of the minute amounts of their salts on a larger amount of a precipitate with a similar crystal structure (the carrier ). The properties were studied, using quantities of the order of 10 g in volumes of... 

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. 

Most chemical iavestigations with plutonium to date have been performed with Pu, but the isotopes Pu and Pu (produced by iatensive neutron irradiation of plutonium) are more suitable for such work because of their longer half-Hves and consequendy lower specific activities. Much work on the chemical properties of americium has been carried out with Am, which is also difficult to handle because of its relatively high specific alpha radioactivity, about 7 x 10 alpha particles/(mg-min). The isotope Am has a specific alpha activity about twenty times less than Am and is thus a more attractive isotope for chemical iavestigations. Much of the earher work with curium used the isotopes and Cm, but the heavier isotopes... 

W. MbUer and R. Lindner, eds.. Transplutonium 1975, 4th International Transplutonium Element Symposium, Proceedings of the Symposium at Baden Baden September 13—17, 1975 W. MbUer and H. Blank, eds.. Heavy Element Properties, 4th International Transplutonium Element Symposium, 5th International Conference on Plutonium and Other Hctinides 1975, Proceedings of the Joint Session of the Baden Baden Meetings September 13, 1975, North-HoUand Publishing Co., Amsterdam, American Elsevier Publishing Co., Inc., New York. 

The primary issue is to prevent groundwater from becoming radioactively contaminated. Thus, the property of concern of the long-lived radioactive species is their solubility in water. The long-lived actinides such as plutonium are metallic and insoluble even if water were to penetrate into the repository. Certain fission-product isotopes such as iodine-129 and technicium-99 are soluble, however, and therefore represent the principal although very low level hazard. Studies of Yucca Mountain, Nevada, tentatively chosen as the site for the spent fuel and high level waste repository, are underway (44). 

AH of the 15 plutonium isotopes Hsted in Table 3 are synthetic and radioactive (see Radioisotopes). The lighter isotopes decay mainly by K-electron capture, thereby forming neptunium isotopes. With the exception of mass numbers 237 [15411-93-5] 241 [14119-32-5] and 243, the nine intermediate isotopes, ie, 236—244, are transformed into uranium isotopes by a-decay. The heaviest plutonium isotopes tend to undergo P-decay, thereby forming americium. Detailed reviews of the nuclear properties have been pubUshed (18). 

Table 5. Thermodynamic Properties and Transition Temperatures for Plutonium MetaC...

Table 6. Phase Relationships and Crystallographic Properties of Plutonium Metal ...

Thermodynamic. The thermodynamic properties of elemental plutonium have been reviewed (35,40,41,43—46). Thermodynamic properties of sohd and Hquid Pu, and of the transitions between the known phases, are given in Table 5. There are inconsistencies among some of the vapor pressure measurements of Hquid Pu (40,41,43,44). 

The chemistry of plutonium ions in solution has been thoroughly studied and reviewed (30,94—97). Thermodynamic properties of aqueous ions of Pu are given in Table 8 and in the Uterature (64—66). The formal reduction potentials in aqueous solutions of 1 Af HCIO or KOH at 25°C maybe summarized as follows (66,86,98—100) ... 

There are numerous complex (ternary and quaternary) plutonium oxides. Their properties have been reviewed (30). Plutonium oxidizes readily to Pu(VI) from binary oxides to complex oxides such as Ba PuO. The best way to oxidize Pu to Pu(VII) is to prepare complex oxides such as Li PuO from Li20 and PUO2 iu flowing oxygen (85). 

Pnictides. Plutonium nitride, PuN, has been studied as a possible fast-reactor fuel. It can be prepared by reaction of PuH with NH at 600—650°C or N2 above 230°C. The pnictides ate also interesting for their soHd-state magnetic and electrical properties. For the latter reason they also have been prepared as single crystals (165). 

M. H. Rand, in G. Kubaschewski, ed., Plutonium Physicochemical Properties of its Compounds and Alloys, Atomic Energy Review, Vol. 4, Special Issue No. 1, IAEA, Vienna, Austria, 1966. 

J. A. Leary, Studies on the Preparation, Properties, and Composition of Plutonium Peroxide, LA-1913, Los Alamos Scientific Laboratory, N.M., 1955. 

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

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 last forty years have seen an extensive, world-wide investigation of the chemical properties of the synthetic element, plutonium. As a result, as much is known about the chemical properties of this element as is known about the chemical properties of most of the naturally occurring elements. The papers in this volume, presented at the Symposium on the Chemistry of Plutonium held during the Kansas City meeting of the American Chemical Society, in September, 1982, represent an up-dating of this large amount of information. 

Investigations of the chemical properties of plutonium have continued in many laboratories throughout the world as it has become available. This has led to the situation where the chemistry of this relative newcomer is as well understood as is that of most of the well-studied elements. The four oxidation states of plutonium—III, IV, V, and VI—lead to a chemistry which is as complex as that of any other element. It is unique among the elements in that these four oxidation states can all exist simultaneously in aqueous solution at appreciable concentration. As a metal, also, its properties are unique. Metallic plutonium has six allotropic forms, in the temperature range from room temperature to its melting point (640 C), and some of these have properties not found in any other known metal. 

This account of the beginnings and early days of the forty years of plutonium chemistry should serve as a background for the following papers which illuminate many of the accomplishments of the intervening years and emphasize the high level of the present status of information on the chemical properties of this remarkable synthetic element. 

Magnetic Properties of Organometallic and Coordination Compounds of Plutonium... 

The known oxidation states of plutonium present a 5f -series, starting from f1 [Pu(VII)] up to f5 [Pu(III)]. But contrary to the 4f - and 5f series across the period table, where the properties can be described by some smooth varying parameters, changing of the oxidation states influences the electronic properties drastically. Due to the large range of available oxidation states plutonium represents a favorable element among the actinides to study these effects. 

Although magnetic properties of a number of plutonium compounds are known, it seems from the above discussion that the knowledge of the electronic ground state properties is very limited. Each compound represents a system of its own which has to be... 

Rand, M.H. in "Plutonium Physico-Chemical Properties of Its Compounds and Alloys" Atomic Energy Review 1966, , Special Issue n° 1, I.A.E.A. Vienna, p. 7. 

Plutonium-noble metal compounds have both technological and theoretical importance. Modeling of nuclear fuel interactions with refractory containers and extension of alloy bonding theories to include actinides require accurate thermodynamic properties of these materials. Plutonium was shown to react with noble metals such as platinum, rhodium, iridium, ruthenium, and osmium to form highly stable intermetallics. 

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