Neptunium(IV) oxide

Cubic

A = 543.4 pm

Np, O

Neptuniumdioxid

Yellow-green to brownish crystalline solid

Fixed

11.1 g · cm -3

2547 ° C

-256.7 ± 0.6 kcal · mol -1

Template: Infobox chemical / molecular formula search is not possible

Neptunium ( IV) oxide or Neptuniumdioxid is chemically most stable oxide of the neptunium.

Properties

Neptuniumdioxid is a yellow-green to brownish crystalline solid with a high melting point of 2547 ° C, it is not very reactive and is almost unaffected by water. Neptuniumdioxid has a cubic crystal system, has the space group Fm3m, the unit cells have a lattice parameter a = 543.4 pm, the structure type is the CaF2 type ( fluorite ) and the coordination numbers are Np, O. The Standardentropie is 19.19 ± 0, 1 cal · mol - 1 · K -1.

Production and representation

Neptuniumdioxid formed by thermal decomposition of oxygen-containing Neptuniumverbindungen, such as the nitrate, oxalate, hydroxide or higher oxides.

It was established in 1944 as the first compound of the then new element.

Use

In the reprocessing of nuclear fuel rods Neptuniumdioxid is obtained as an intermediate product. As a chemically stable form of neptunium it finds itself in turn use in nuclear fuel rods. There is (especially the isotope together with minor amounts of other 237Np Neptuniumisotope ) separated from the spent nuclear reactor fuel rods, and placed in containing only Neptuniumdioxid. They are re-inserted into the nuclear reactor where they are again irradiated with neutrons; from the 237Np 238Pu is bred.

The representation of the neptunium ( IV) chloride can be achieved by reaction of tetrachloromethane with Neptuniumdioxid at higher temperatures.

Safety

Classifications according to the Hazardous Substances Ordinance are not available because they only include the chemical danger and play a very minor role compared to the risks based on the radioactivity. Even the latter applies only if there is a relevant material for this amount.