Plutonium melting point

Thermal Expansion. Coefficients of linear thermal expansion and linear expansion during transformation are listed in Table 7. The expansion coefficient of a-plutonium is exceptionally high for a metal, whereas those of 5- and 5 -plutonium are negative. The net linear increase in heating a polycrystalline rod of plutonium from room temperature to just below the melting point is 5.5%. 

A good deal was learned about plutonium metal, including the determination of its density by both capillary displacement and x-ray diffraction methods, its melting point and vapor pressure. 

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 PUCI3 also acts as a salt-phase buffer to prevent dissolution of trace impurities in the metal feed by forcing the anode equilibrium to favor production (retention) of trace impurities as metals, instead of permitting oxidation of the impurities to ions. Metallic impurities in the feed fall into two classes, those more electropositive and those less electropositive than plutonium. Since the cell is operated at temperatures above the melting point of all the feed components, and both the liquid anode and salt are well mixed by a mechanical stirrer, chemical equlibrium is established between all impurities and the plutonium in the salt even before current is applied to the cell. Thus, impurities more electropositive than the liquid plutonium anode will be oxidized by Pu+3 and be taken up by the salt phase, while impurities in the electrolyte salt less electropositive than plutonium will be reduced by plutonium metal and be collected in the anode. 

The electrolyte salt must be processed to recover the ionic plutonium orginally added to the cell. This can be done by aqueous chemistry, typically by dissolution in a dilute sodium hydroxide solution with recovery of the contained plutonium as Pu(OH)3, or by pyrochemical techniques. The usual pyrochemical method is to contact the molten electrolyte salt with molten calcium, thereby reducing any PUCI3 to plutonium metal which is immiscible in the salt phase. The extraction crucible is maintained above the melting point of the contained salts to permit any fine droplets of plutonium in the salt to coalesce with the pool of metal formed beneath the salt phase. If the original ER electrolyte salt was eutectic NaCl-KCl a third "black salt" phase will be formed between the stripped electrolyte salt and the solidified metal button. This dark-blue phase can contain 10 wt. % of the plutonium originally present in the electrolyte salt plutonium in this phase can be recovered by an additional calcium extraction stepO ). 

The melting point of plutonium is 640°C, its boiling point is 3,232°C, and its density is over 19 times that of the same volume of water (19.84g/cm ). 

After the discovery of plutoninm and before elements 95 and 96 were discovered, their existence and properties were predicted. Additionally, chemical and physical properties were predicted to be homologous (similar) to europium (gjEu) and gadolinium ( Gd), located in the rare-earth lanthanide series just above americium (gjAm) and curium ((,jCm) on the periodic table. Once discovered, it was determined that curium is a silvery-white, heavy metal that is chemically more reactive than americium with properties similar to uranium and plutonium. Its melting point is 1,345°C, its boihng point is 1,300°C, and its density is 13.51g/cm. ... 

Proceeding from thorium to plutonium along the actinide series, the vapor pressure of the corresponding iodides decreases and the thermal stability of the iodides increases. The melting point of U metal is below 1475 K and for Np and Pu metals it is below 975 K. The thermal stabilities of the iodides of U, Np, and Pu below the melting points of the respective metals are too great to permit the preparation of these metals by the van Arkel-De Boer process. 

Plutonium metal exhibits the most complex series of crystalline phases of any known element. At normal pressure there are six metallic phases of Pu between room temperature and its 913 K melting point (60). 

The Viscosity of Liquid Plutonium, predicted from a General Relationship between the Activation Energy and Melting Points of Metals, and the Experimental Data. J. Inorg. Nucl. Chem. 25, 137 (1963). 

As Indicated previously, the tentative phase diagram of the Pu-0 system shows plutonium sesquioxide as a line compound from room temperature up to its melting point. During the course of the preparation of for low temperature heat capacity... 

Actinide nitrides are known for Th through Cm. All of the nitrides are high melting compounds with melting points of 2630 °C, 2560 °C, and 2580 °C for Th, Np, and Pu, respectively. The actinide nitrides can decompose to give N2. Thorium, uranimn, and plutonium nitrides are well known and can be used as nuclear fiiels. Fuels of this type, especially uranium and mixed uranium plutonium nitrides, can be used in lead-cooled fast reactors, which have been proposed as a possible next-generation nuclear reactor and for use in deep-sea research vehicles. 

The metallurgical properties of metallic plutonium are even more unfavourable than those of uranium. The melting point of Pu is 639 °C and six solid phases are known. Furthermore, the critical mass of a reactor operating with pure Pu as fuel is below 10 kg, and it would be very difficult to take away the heat from such a small amount of material. A great number of plutonium alloys have been investigated with respect to their possible use as nuclear fuel, but they have not found practical application. 

Plutonium is a silvery-white metal with a melting point of 1,183°F (639.5°C) and a density of 19.816 grams per cubic centimeter, nearly 20 times the density of water. 

At its melting point (624°C), the density of solid plutonium is 16.24 g cm. The density of liquid plutonium is 16.66 g cm. A small sample of liquid plutonium at 625°C is strongly compressed. Predict what phase changes, if any, will occur. 

Plutonium dioxide is the form of plutonium most commonly specified for fuel for power reactors. It has the same general features already described for pure UO2 fuel, such as high melting point, irradiation stability, compatability with metals and with reactor coolants, and ease of preparation. In most designs of plutonium-fueled power reactors the fuel is a mixture of uranium and plutonium oxides. 

The complete miscibility of the stoichiometric uranium-plutonium dioxide results in the simple liquidus-solidus melting-point curves of Fig. 9.5. The curves are consistent with ideal-... 

The thermodynamically favorable reduction of PuOj with calcium has the disadvantage that the CaO coproduct is not molten, so that the resulting plutonium metal and umeacted calcium metal remain finely dispersed throughout the slag. However, the dispersed plutonium can be recovered as a massive metal by preferentially extracting the calcium oxide and unreacted calcium with molten calcium chloride at a temperature above the melting points of plutonium and calcium, leaving consolidated plutonium metal with yield efficiencies in excess of 99.9 percent [W1 ]. 

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