Neptunium radioactive decay series

FlC- 1-2, The three naturally occurring radioactive decay series and the man-made neptunium series. Although (which is the parent to the actinium series) and (which is the parent to the thorium series) have been discovered in nature, die decay series shown here begin with the most abundant Icmg-Uved nuclides. 

A fourth long radioactive decay series, the neptunium series (Fig. 1.2), is conqxrsed of nuclides having mass numbers which divided by 4 have a remainder of 1 (the 4n + 1 series). The name comes from the longest lived A = 4n + I nuclide heavier than Bi, Np, which is considered as the parmt species it has a half-life of 2.14 X 10° y. Inasmuch as this half-life is considerably shorter than the age of the earth, primordial Np no longer exists on earth, and, therefore, the neptunium series is not found as a natural... 

The only nonnaturaUy occurring radioactive decay series, the neptunium series, has a formula ... 

Actinides in the environment can be classified into two groups (i) the uranium and thorium series of radionuclides in the natural environment and (ii) neptunium, plutonium, americium and curium which are formed in a nuclear reactor during the neutron bombardment of uranium through a series of neutron capture and radioactive decay reactions. Transuranics thus produced have been spread widely in the atmosphere, geosphere and aquatic environment on the earth, as a result of nuclear bomb tests in the atmosphere, and accidental release from nuclear facilities (Sakanoue, 1987). Most of these radionuclide inventories have deposited in the northern hemisphere following the tests conducted by the United States and the Soviet Union. 

FIGURE 1.6 The artificial radioactive decay chain of the 4n -t 1 series, beginning with neptunium-237, deeaying through uranium-233 and ending with thallium-205. 

Within a day, Abelson recalls, I established that the 2.3-day activity had chemical properties different from those of any known element. [It] behaved much like uranium. Apparently the transuranics were not metals like rhenium and osmium but were part of a new series of rare-earth-like elements similar to uranium. For a rigorous proof that they had found a transuranic the two men isolated a pure uranium sample with strong 23-minute U239 activity and demonstrated with half-life measurements that the 2.3-day activity increased in intensity as the 23-minute activity declined. If the 2.3-day activity was different chemically from any other element and was created in the decay of U239, then it must be element 93. McMillan and Abelson wrote up their results. McMillan had already thought of a name for the new element— neptunium, for the next planet out beyond Uranus—but they chose not to offer the name in their report. They mailed the report, Radioactive element 93, to the Physical Review on May 27, 1940, the same day Louis Turner sent Szilard his transuranic theories anticipation and discovery can cut that close in science. 

Elements with atomic numbers greater than uranium ( U), the element with the highest atomic number found in nature, are called transuranium elements. All the transuranium elements of the actinide series were discovered as synthetic radioactive isotopes at the University of California at Berkeley or at Argonne National Laboratory. By colliding uranium ( U) with neutrons, they produced uranium ( U), which days later decayed to neptunium (" "Np). 

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