Neptunium




 * Atomic Number:** 93
 * Atomic Weight:** 237
 * Melting Point:** 917 K (644°C or 1191°F)

Radioactive and Artificially Produced __**Neptunium**__ Is a [|chemical element] with the symbol **Np** and [|atomic number] 93. A [|radioactive] metal, neptunium is the first [|transuranic element] and belongs to the [|actinide] series. Its most stable [|isotope], 237Np, is a by-product of [|nuclear reactors] and [|plutonium] production and it can be used as a component in [|neutron detection] equipment. Neptunium is also found in trace amounts in [|uranium] ores due to transmutation reactions
 * Boiling Point:** 4175 K (3902°C or 7056°F)
 * Density:** 20.25 grams per cubic centimeter
 * Phase at Room Temperature:** Solid
 * Element Classification:** Metal
 * Period Number:** 7 **Group Number:** none **Group Name:** Actinide

Being similar to Uranium, Neptunium is a radioactive metallic element and is a constant occurrence in reactors because it is a bi product from the production of Plutonium.

Neptunium got it's name after the planet Neptune and is a man-made element. __**Neptunium History**__ Neptunium was the first synthetic transuranium element of the actinide series. It was discovered by McMillan and Abelson in 1940 at Berkeley, California, USA, who bombarded uranium with neutrons produced from a cyclotron. It was the first synthetic transuranium (elements after uranium) element discovered.

__** Occurrence **__ Trace amounts of neptunium are found naturally as decay products from transmutation reactions in uranium ores. Artificial 237Np is produced through the reduction of 237NpF3 with barium or lithium vapor at around 1200 °C and is most often extracted from spent nuclear fuel rods as a by-product in plutonium production. 2 NpF3 + 3 Ba → 2 Np + 3 BaF2 By weight, neptunium-237 discharges are about 5% as great as plutonium discharges and about 0.05% of spent nuclear fuel discharges. __** Characteristics **__ Silvery in appearance, neptunium metal is chemically fairly reactive and is found in at least three allotropes: > Neptunium has the largest liquid range of any element, 3363 K, between the melting point and boiling point. It is the densest element of all actinoids.α-neptunium, orthorhombic, density 20.45 g/cm3
 * β-neptunium (above 280 °C), tetragonal, density (313 °C) 19.36 g/cm3
 * γ-neptunium (above 577 °C), cubic, density (600 °C) 18 g/cm3

Neptunium, like [|protactinium], [|uranium] , [|plutonium] , and [|americium] readily forms a linear dioxo neptunyl core (NpO2n+), in its 5+ and 6+ oxidation states, which readily complexes with hard O-donor ligands such as OH–, NO2–, NO3–, and SO42– to form soluble anionic complexes which tend to be readily mobile with low affinities to soil. - often a by product of nuclear reactors
 * NpO2(OH)2–
 * NpO2(CO3)–
 * NpO2(CO3)23–
 * NpO2(CO3)35–

Role in nuclear waste Neptunium-237 is the most mobile actinide in the deep geological repository environment.[19home] This makes it and its predecessors such as americium-241 candidates of interest for destruction by nuclear transmutation.[20home] Neptunium accumulates in commercial household ionization-chamber smoke detectors from decay of the (typically) 0.2 microgram of americium-241 initially present as a source of ionizing radiation. With a half-life of 432 years, the americium-241 in a smoke detector includes about 3% neptunium after 20 years, and about 15% after 100 years. Due to its long half-life neptunium becomes the major contributor of the total radiation in 10,000 years. As it is unclear what happens to the containment in that long time span, an extraction of the neptunium would minimize the contamination of the environment if the nuclear waste could be mobilized after several thousand years.[21home][22home]