Neptunium nuclear properties

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. 

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 9.11 lists the isotopes of neptunium important in nuclear technology and some of their important nuclear properties. 

The first transuranium elements, neptunium and plutonium, were obtained in tracer amounts from bombardments of uranium by McMillan and Abelson and by Seaborg, McMillan, Kennedy, and Wahl, respectively, in 1940. Both elements are obtained in substantial quantities from the uranium fuel elements of nuclear reactors. Only plutonium is normally recovered and is used as a nuclear fuel since, like 235U, it undergoes fission its nuclear properties apparently preclude its use in hydrogen bombs. Certain isotopes of the heavier elements are made by successive neutron capture in 239Pu in high-flux nuclear reactors (> 1015 neutrons cm-2 sec- ). Others are made by the action of accelerated heavy ions of B, C, N, O or Ne on Pu, Am or Cm. 

The neutron, being uncharged, is not repelled by the positive charge on the nucleus, and makes an ideal nuclear probe. Soon after the discovery of this property many experiments were carried out to try to make new elements that were more massive than uranium by bombarding heavy atoms, notably U itself, with neutrons. Two such elements that can be made this way are neptunium, Np, and plutonium, Pu ... 

The a-emitting product was identified as a new element fi-om the study of chemical behavior of this isotope. It was distinctly different from both uranium and neptunium in its redox properties the 3+ and 4+ valence states were more stable. A second isotope of element 94, Pu, with a half-life of24,000 years was synthesized immediately as a daughter of P decay of Np, which confirmed the presence of element 94. The isotope Pu produced in appreciable amounts in nuclear reactors is of major importance, because of its large fission cross section with thermal neutrons. It was named after the planet Pluto in analogy to uranium and neptunium. 

A huge amount of research has been done on the solid compounds of transuranium elements. In this section, fundamental properties of oxide and some compounds of the transuranium elements are briefly overviewed. The oxygen to metal ratio (O/M ratio) is one of the important parameters to understand the solid-state behavior of these oxides. The fluorite-structure dioxide is well studied in the research of mixed oxide (MOX) nuclear fuels. O Table 18.14 gives fundamental properties of transuranium oxides (Morss 1991). Neptunium... 

Plutonium and neptunium nitrides were studied for the application to advanced fast breeder reactor (FBR) fuels. Details on the application of nuclear fuels is available in the reference (Matzke 1986). Fundamental properties of these plutonium and neptunium compounds are reviewed in the Chemical Thermodynamics of Neptunium and Plutonium (Lemire et al. 2001) issued by OECD/NEA (Organization for Economic Co-operation and... 

Duplessis, J. and Guillaumont, R. (1977) Hydrolyse du neptunium tetravalent. Radiochem. Radioanal. Lett, 31, 293-302. Edelstein, N., Bucher, J., Silva, R.J. and Nitsche, H. (1983) Thermodynamic Properties of Chemical Species in Nuclear Waste. Technical Report, ONWI-399 Lawrence Berkeley Laboratory, 125 pp. Ekberg, C., Brown, P., Comarmond, J., and Albinsson, Y. (2001) On the hydrolysis of tetravalent metal ions. Mater. Res. Soc. Symp. Proc., 663, 1091-1099. 

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