Transuranic elements neptunium

To estimate the environmental impact caused by nuclear fuel cycle of the SVBR-75/100, the value of specific radiotoxicity of the produced transuranic elements (neptunium, plutonium, americium and curium) and long-lived fission products (technetium-99, iodine-129 and caesium-135) was taken as a criterion, as a function of the electric energy produced. When this value decreases with energy production, the environmental impact of the nuclear fuel cycle can be considered friendly . The radiotoxicity characteristic adopted was the volume of water necessary to dilute some quantity of radionuclides to the concentrations for which the specific radioactivity of the solution meets the sanitary requirements for drinking water. 

The transuranic elements are a subseries within the actinide series with atomic numbers higher than uranium They include the actinides neptunium (53NP) up to... 

Of some interest is that after uranium ( jU) was named after the planet Uranus, neptunium (jjNp), which was discovered next, was named after Neptune, the next planet in our solar system. And Anally, plutonium (g4Pu) the next transuranic element discovered, was named after Pluto, the last planet discovered so far in our solar system. 

Neptunium has an affinity for combining with nonmetals (as do all transuranic elements) such as oxygen, the halogens, sulfur, and carbon. 

Isomorphism among compounds of the actinides is common and only a few examples need be given. The dioxides, MO2, of thorium, uranium, neptunium, plutonium and americium all have a fluorite lattice. The trihalides of the transuranic elements are isomorphous not only with the corresponding trihalides of actinium and uranium but also with those of the lanthanides. Isomorphism is also exhibited in many complex halides thus thorium, ura-... 

Only five transuranic elements exist or are anticipated to be produced in amounts which could lead to significant environmental concentrations. These are neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), and californium (Cf). Of these five, only two, plutonium and americium, have been detected and measured already in the marine environment as a result of global fallout of nuclear testing debris. The procedures described below were developed specifically to measure plutonium and americium. However, as will be expanded later, the techniques for measuring americium are also able to detect curium and californium should they be present in significant amounts in the future. 

One of the requirements of any nuclear facility is to monitor the effluent uxiste water to show compliance with existing standards. This paper describes a sequential procedure for the separation of the transuranic elements from water samples up to 60 1. The elements of interest are coprecipitated with calcium fluoride and then individually separated using a combination of ion exchange and solvent extraction, with a final sample preparation by electrodeposition. Alpha spectrometry of these samples allows the measurement of neptunium, plutonium, and transplutonium nuclides at sub-fCi/l, levels. 

The first transuranic element was produced in 1940. Neptunium (Z = 93) results from the capture of a neutron by U, followed by beta decay. Subsequent work by the American chemist Glenn Seaborg and others led to the production of plutonium (Z = 94) and heavier elements. In recent years, nuclides with Z as high as 116 have been made, but in tiny quantities. These nuclides have very short half-lives. 

Early Work. The irradiated fuel, upon discharge from the reactor, comprises the residual unbumt fuel, its protective cladding of magnesium alloy, zirconium or stainless steels, and fission products. The fission process yields over 70 fission product elements, while some of the excess neutrons produced from the fission reaction are captured by the uranium isotopes to yield a range of hew elements—neptunium, plutonium, americium, and curium. Neutrons are captured also by the cladding materials and yield a further variety of radioactive isotopes. To utilize the residual uranium and plutonium in further reactor cycles, it is necessary to remove the fission products and transuranic elements and it is usual to separate the uranium and plutonium this is the reprocessing operation. 

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. 

In the determination of transuranium elements (or nuclides), the most important step is separation of the elements from the sample matrix. Differences in redox properties are used for the separation of the first four elements in the series (neptunium, plutonium, americium, curium). Since the higher members exist primarily in the same oxidation state (III), separation by ion-exchange chromatography is commonly used. The lighter transuranic elements can be determined by common chemical methods, and trace amounts are usually determined by radiometric methods such as a-spectrometry. 

J3AI + Jn iiNa + pie represents the bombardment of aluminum with neutrons to produce an isotope of sodium and helium nuclei (alpha particles). All transuranic elements above curium, atomic number 96, are artificially radioactive because they do not occur in nature. Even neptunium, plutonium, americium. 

Transuranic wastes are so called because they contain isotopes of elements heavier than uranium, primarily plutonium, americium, and neptunium. Since these isotopes emit alpha particles. 

---