Neptunium synthesis

Kilogram amounts of neptunium ( Np) have been isolated as a by-product of the large-scale synthesis of plutonium in nuclear reactors that utilise 235u and 238u as fuel. The following transmutations occur ... 

One of the major advances of science in the first half of this century was the synthesis of ten elements beyond uranium. Glenn T. Seaborg participated in the discovery oj most of these, a sufficient tribute to his outstanding ability as a scientist. For the first such discoveries, those of neptunium and plutonium, he shared with Professor Edwin M. McMillan the Nobel Prize in Chemistry for 1951. 

Synthesis of plutonium in significant quantities requires a sufficiently long reactor fuel irradiation period. Uranium, plutonium, and the fission products obtained after neutron irradiation are removed from the reactor and stored under water for several weeks. During such cooling periods most neptunium-239 initially formed from uranium and present in the mixture transforms to plutonium-239. Also, the highly radioactive fission products, such as xenon-133 and iodine-131 continue to decay during this period. 

Seaborg s contributions illustrate how certain areas of science can be highly influenced by a particular institution or even a national tradition over time. His discovery of plutonium at the University of California at Berkeley followed the 1940 synthesis of neptunium at the same site by Edwin... 

Synthesis and Characterization of Protactinium(IV), Neptunium(IV), and Plutonium (IV) Borohydrides... 

Bamberger also applied a similar metathesis reaction process to the synthesis of phosphates of uranium and neptunium, thus this represents a versatile and alternative synthesis method for the conversion of rare-earth oxides or halides to the phosphate form. 

So, it seems that of these 92 natural elements, only 88 can be considered naturally occurring since the above four are transient species, newly formed by radioactive decay. Neptunium and plutonium can similarly be found in ultratrace quantities due to de novo synthesis coupled to rapid decay. We could stretch a point by noting that all helium on our planet is also formed de novo. However, although these fresh helium atoms are lost into space, the nuclei are totally stable. 

Early in 1940 McMillan and Abelson in the United States synthesized and identified a new element with atomic number 93 to which they gave the name neptunium. The reaction used in the synthesis was... 

The history of syntheses saw its periods of breakthroughs and slack periods. The first breakthrough period was from 1940 to 1945 when four transuranium elements were synthesized, namely, neptunium (Z = 93), plutonium (Z = 94), americium (Z = 95), and curium (Z = 96). The period till 1949 was a slack time and no new elements were discovered. In the next breakthrough period from 1949 to 1952 four more transuranium elements were added to the periodic system, namely berklium (Z = 97), californium (Z = 98), einsteinium (Z = 99), and fermium (Z = 100). In 1955, fifteen years after the synthesis of the first transuranium element, one more element, mendelevium (Z = 101), was synthesized. The next 25 years saw much less syntheses and only six new elements appeared in the periodic system. Here scientists encountered an entirely new situation and many former criteria for evaluating discoveries of elements proved inapplicable. 

Synthesis of neptunium exhibited a significant feature which was to prove typical for syntheses of all transuranium elements (and other synthesized elements, too). First, one isotope with a certain mass number was synthesized. For neptunium this was neptunium-239. From that time it became a rule to date a discovery of a new transuranium element by the time of reliable synthesis of its first isotope. But sometimes this isotope proved to be so short-lived that it was difficult to subject it to physical and chemical analyses let alone find a useful application for it. A study of a new element would best be conducted with its longest-lived isotope. In the case of neptunium this was iieptunium-237 synthesized in 1942 in the following reaction ... 

The work on the synthesis of element 94 was headed by the famous American scientist G. Seaborg whose group discovered many transuranium elements. During the winter of 1940-1941 they studied the nuclear reaction U(d, 2n) which gave rise to the isotope neptunium-238. An alpha-active substance accumulated with time in the reaction product. The scientists extracted this substance and found... 

X-ray powder diffraction data reveal that CP3UCI and Cp3ThCl are isomor-phous. Tris(cyclopentadienyl)thorium derivatives of other halides, alkoxides, tetrahydroborates, etc., can be prepared in a manner analogous to the uranium reaction above [58]. Tris(cyclopentadienyl)neptunium chloride, Cp3NpCl, can be prepared either by a radiochemical synthesis [75] ... 

Cyclo-octatetraene complexes of trivalent actinides have also been prepared. The synthesis of anionic neptunium and plutonium complexes is shown below [169] ... 

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