Neptunium traced with

Planet pluto) Plutonium was the second transuranium element of the actinide series to be discovered. The isotope 238pu was produced in 1940 by Seaborg, McMillan, Kennedy, and Wahl by deuteron bombardment of uranium in the 60-inch cyclotron at Berkeley, California. Plutonium also exists in trace quantities in naturally occurring uranium ores. It is formed in much the same manner as neptunium, by irradiation of natural uranium with the neutrons which are present. 

Fermi s pile turned out to be a plant which efficiently manufactured a new element in large quantities. This element is plutonium. It is a brand new man-made chemical element which fissons just as easily as U-235. The story of the birth of this synthetic element goes back to a day in May, 1940, when two men using Lawrence s cyclotron at Berkeley, California, bombarded uranium with neutron bullets. The two men were Edwin M. McMillan and Philip H. Abelson. After the bombardment of U-238 they detected traces of a new element, heavier than uranium. This new element, No. 93, was named neptunium by McMillan. It was a very difficult element to study, for its life span was very short. It threw out neutrons immediately and in a split second was no longer neptunium. 

DU has 40% less radioactivity than natural uranium, but may contain trace levels of plutonium, neptunium, americium, technetiiun, and U, which increase the radioactivity by 1% but are insignificant with respect to chemical and radiological toxicity (Force Health Protection Readiness Policy Programs, 2008 Sztajnkrycer and Often, 2004 WHO, 2001). Because of the decreased radioactivity of DU, it is believed that DU is a safer form than natural uranium, while maintaining the same chemical properties. As the heaviest occurring element, uranium is extremely dense and both uranium and DU are often used in applications which require such dense metals. 

According to aircraft measurements within the USSR, the plume height exceeded 1200 m on 27 April and on subsequent days, the plume height did not exceed 200-400 m. The volatile elements iodine and caesium, were detectable at greater altitudes (6-9 km), with traces also in the lower stratosphere (Jaworowski et al., 1988). The refractory elements, such as cerium, zirconium, neptunium and strontium, were for the most part of significance only in local deposition within the USSR. 

For hexavalent neptunium the lengthening of An-N distances is also observed, but the correlation with coordination mode is not traced the identical values (2.564 A) were found in the complexes with Py 27 and Bipy 29 (Table 17). 

The sucessful experiments for the retention of plutonium onto alumina from TTN0 -HF solution gave enough confidence to recomend the proposed method to separate traces of plutonium from waste solutions in the presence of macroamounts of uranium (VI). Of course, only macroamounts of thorium, uranium (IV) and rare earths are serious interfering ions, since they precipitate with HF. The behavior expected for neptunium in the same system should be similar to plutonium, thorium and rare earths. The retention of neptunium from HNO - HF solutions is in progress. The sorption yield for Pu was around 95%. The sorption mechanism is not well established. Figure 3 shows the proposed flowsheet for recovery of Pu traces from reprocessing waste solutions. 

The initial countercurrent extraction stages transfer the U and Pu to the organic or TBP phase with the fission products and the higher actinides remaining in the aqueous phase. Beyond the feed point, the organic phase continues to extraction stages where it is scrubbed with acid to remove traces of the fission products. Americium and curium in the - -3 state stay in the aqueous phase. Neptunium is partially in the -b6 (extractable) and the +5 state, so it splits between the organic and the aqueous phases. Careful control... 

Neptunium was the first of these to be synthesised it was obtained in traces by bombardment of U(238) with neutrons (see Fig. 9(a), p. 318). Its chemical properties are not in general like those of rhenium or the other elements of Group vii. It yields no volatile oxide corresponding to RejO,. It functions with valencies 3, 4, 5 and 6 and in its higher stages of oxidation it tends to resemble uranium. Several isotopes are known including 237, 238 and 239. It was named after the planet Neptune discovered in 1846. 

In a modern PUREX plant, the fuel pins are first cut into pieces that are 3-5 cm long. The fuel is then dissolved in 6-11 M nitric acid, while the cladding hulls do not dissolve. Sometimes <0.05 M AIF3 is added to the nitric acid to improve dissolution of, e.g., zirconium by complex formation. The solution is then diluted to 3-4 M and nitrite is added to assure that plutonium is present as Pu(IV) and uranium as U(VI). Plutonium and uranium are then selectively extracted into TBP in aliphatic kerosene. Fission products and trivalent actinides remain in the aqueous phase. The extract is scrubbed with nitric acid to remove all contaminants except traces of ruthenium, neptunium, and zirconium. 

The uranium fraction is concentrated by evaporation and nitric acid is added to -S M. Uranium is then extracted into a TBP solution that is scrubbed with a reducing solution to remove traces of plutonium and neptunium. This process is repeated twice. Then uranium is back-extracted into 0.01 M nitric acid and converted to uranium oxide. 

The first synthetic actinide element, neptunium, was discovered in 1040. The last element of the actinide series, lawrencium, was created for the first time in 1061. These and the nine other intervening elements have added a new dimension to science, technology, industry, medicine, and politics in an e aordinarily short period of time. Each synthetic actinide element from atomic number 03 to atomic number 98 (with the exception of berkelium, atomic number 07) can now be manufactured in essentially any desired quantity, a truly remarkable achievement. The high points of the history of the actinide elements are traced, production methods are described, and a forecast is given of the manufacturing levels to be expected during the next decade. An analysis is presented of the current and near-term implications the various isotopes of the actinide elements. 

Radiochemical analyses of PWR primary coolant show that the major fraction of the neptunium and plutonium traces in the coolant is usually associated with the corrosion product suspended solids and that it can be removed from the coolant by filtering. Only in cases of very low corrosion product concentrations in the coolant were significant proportions of the transuranium elements observed to be present in a dissolved (i. e. non-filtrable) form. As yet, it is not known whether mixed oxide formation between magnetite-type oxides and these elements is responsible for this behavior or whether the actinide traces are adsorbed by van de Waals forces onto the large surface areas of the finely dispersed suspended solids. Under constantload operation conditions and as long as no additional fuel rod failures occur, the activity ratio Pu Co in the corrosion products remains virtually constant over time, thus indicating a similar behavior of these different elements in the coolant. 

The series in Figure 23.3 is one of three that occur in nature. All end with isotopes of lead, whose nuclides all have one (Z = 82) or two N = 126, Z = 82) magic numbers. A second series begins with uranium-235 and ends with lead-207, and a third begins with thorium-232 and ends with lead-208. (Neptunium-237 began a fourth series, but its half-life is so much less than the age of Earth that only traces of it remain today.)... 

---