Plutonium atomic properties

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. 

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. 

Apart from d- and 4f-based magnetic systems, the physical properties of actinides can be classified to be intermediate between the lanthanides and d-electron metals. 5f-electron states form bands whose width lies in between those of d- and 4f-electron states. On the other hand, the spin-orbit interaction increases as a function of atomic number and is the largest for actinides. Therefore, one can see direct similarity between the light actinides, up to plutonium, and the transition metals on one side, and the heavy actinides and 4f elements on the other side. In general, the presence or absence of magnetic order in actinides depends on the shortest distance between 5f atoms (Hill limit). 

The first part of the chapter is devoted to an analysis of these correlations, as well as to the presentation of the most important experimental results. In a second part the following stage of development is reviewed, i.e. the introduction of more quantitative theories mostly based on bond structure calculations. These theories are given a thermodynamic form (equation of states at zero temperature), and explain the typical behaviour of such ground state properties as cohesive energies, atomic volumes, and bulk moduli across the series. They employ in their simplest form the Friedel model extended from the d- to the 5f-itinerant state. The Mott transition (between plutonium and americium metals) finds a good justification within this frame. 

The trends in several ground state properties of transition metals have been shown in Figs. 2, 3 and 15 of Chap. A and Fig. 7 of Chap. C. The parabolic trend in the atomic volume for the 3-6 periods of the periodic table plus the actinides is shown in Fig. 3 of Chap. A. We note that the trend for the actinides is regular only as far as plutonium and that it is also broken by several 3 d metals, all of which are magnetic. Similar anomalies for the actinides would probably be found in Fig. 15 of Chap. A - the bulk modulus - and Fig. 7 of Chap. C - the cohesive energy if more measurements had been made for the heavy actinides. 

All the early work on plutonium was done with unweighable amounts on a tracer scale. When it became apparent that large amounts would be needed for the atomic bomb, it was necessary to have a more detailed knowledge of the chemical properties of this element. Intensive bombardment of hundreds of pounds of uranium was therefore begun in the cyclotrons at Berkeley and at Washington University in St. Louis. Sepa-ration of plutonium from neptunium was based on the fact that neptunium is oxidized by bromate while plutonium is not, and that reduced fluorides of the two metals are carried down by precipitation of rare earth fluorides, while the fluorides of the oxidized states of the two elements are not. Therefore a separation results by repeated bromate oxidations and precipitations with rare earth fluorides. 

The properties of isotopes. Packing fraction. Structure of atomic nuclei. Nuclear fission. Nuclear chain reaction. Manufacture of plutonium. Fission of U23 and Pu23 . Uranium reactors the uranium pile. Nuclear energy as a source of power. 

II. International Atomic Energy Agency The Plutonium-Oxygen and Uranium-Plutonium-Oxygen Systems A Thermochemical Assessment, Report of a Panel on Thermodynamic Properties of Plutonium Oxides, Vienna, Oct. 1966, Tech. Rept. Series No. 79, Vieima, 1967. 

R2. Rand, M. H. Iliennochemical Properties, in Atomic Energy Review, vol. 4, Plutonium Physico-Chemical Properties of Its Compounds and Alloys, Special Issue No. 1, International Atomic Energy Agency, Vieima, 1966. 

Cf is made by bombarding plutonium-239 ( Pu) with neutrons in a very high intensity nuclear reactor. Elements of higher atomic number are buUt up by successive neutron captures. Thirteen successive neutrons must be added to each nucleus of Pu to convert it to The important nuclear properties of this new element are ... 

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