Protactinium formation

Koetsier G, Elliott T, Fruijtier C (1999) Constraints on diagenetic age disturbance combined uranium-protactinium and uranium-thorium ages of the key Largo Formation, Florida Keys, USA. Ninth Atmual V. M. Goldschmidt Conf 157-158... 

Bromofluorobenzene, formation by nuclear activation, 5 191-192 Bromofluorophosphine, 13 378-380 Bromopiotactinates, see Protactinium, bromo complexes of... 

The element is difficult to maintain in aqueous solution in the form of simple salts. Solubility data seem to indicate that such amounts as can be dissolved probably do so entirely by formation of complex ions. Fluoride ion strongly complexes protactinium, and it is due to this that protactinium compounds are in general soluble in hydrofluoric acid. 

Actinium and protactinium are present in uranium minerals but recovery is not generally practiced. Neptunium (237Np and 239Np) and plutonium (M9Pu) are present in minute amounts in uranium ores because they result from reaction of neutrons with uranium isotopes, not due to survival from primordial formation. All other actinides are entirely synthetic. Methods of preparation for those up to Cf are given in Table 20-2 syntheses of the other elements are noted in Section 20-18. 

While protactinium is present at less than the parts per million level in uranium ores, this is still the major source because it can be extracted from the residues accumulated in large-scale production of uranium. There are extreme technical difficulties because of colloid formation but more than 100 g have been isolated. 

Attempts to prepare protactinium pentanitrate by reacting penta-halides with liquid dinotrogen pentoxide have resulted in the formation of HPalNOglfl, possibly as a result of traces of anhydrous nitric acid present in the N Os 49). The presence of the jiroton has not been confirmed by electron spin resonance studies, but infrared results have shown that all the nitrate is covalently bound and vibrations associated with the nitronium and nitrosonium cations were not observed. Niobium and tantalum pentahalides react under similar conditions to form the anhydrous oxytrinitrates, M 0(N0g)3 20, 87). 

The fiuorosulfate dihydrate, PaF2S04 2H2O, analogous to the known uranium(IV) compound (1S2), is precipitated on the addition of aqueous hydrofluoric acid to solutions of protactinium(IV) in dilute sulfuric acid (131). Others (71, 84) have reported the formation of a white, insoluble precipitate in hydrofluoric acid, believed to be a tetrafluoride hydrate, but the product has not been completely characterized. 

The first reliable information on the protactinium-carbon system was reported by Lorenz and ScherfF who prepared the monocarbide, PaC, by carbothermic reduction of Pa20s. The dioxide, Pa02, is first obtained at approximately 1100°C and is then converted to PaC above 1900°C. In the presence of excess carbon there is some evidence for the formation of the tetragonal dicarbide. Protactinium monocarbide is isostructural with other actinide monocarbides possessing the fee NaCl-type of structure with Oo = 5.0608 A. In contrast to ThC and UC, however, it is stable in the atmosphere and is relatively inert toward acid solutions. By measuring the CO equilibrium pressures for the reaction,... 

A series of nuclear reactions that begins with an unstable nucleus and results in the formation of a stable nucleus is called a radioactive decay series. As you can see in Figure 25-11, uranium-238 first decays to thorium-235, which in turn decays to protactinium-234. Decay reactions continue until a stable nucleus, lead-206, is formed. 

A. Actinyl V s and Vi s give monomeric oxo cations in acid, in contrast to the d element proclivity towards polymerization (isopoly acid formation). Protactinium is similar to d elements in this regard. 

The acetylacetonate PajacacjgClg has been prepared by direct reaction between protactinium pentachloride and acetylacetone in methylene dichloride. The addition of isopentane to this reaction mixture results in the formation of long, bright yellow needles of the complex, and single crystal studies have shown these to possess monoclinic symmetry, space group P2i/c with do = 8.01, = 23.42, Cq = 18.63 A, and... 

Beta emission Beta particles (P ) are emissions having medium level penetration. They are fast traveling electrons. As a result of beta emission, the resulting atom will have an increase in the atomic number by 1. There is no change in the mass number. In the process, there is also a proton formation from the neutron inside the nucleus, along with the electron formation. In the following example, thorium-234 decays to protactinium-234 by emitting a beta particle. 

Non-productive neutron absorption in the absorption zone, however, has a more serious effect. For example, protactinium is an intermediate stage between the thorium and the uranium isotope desired, and as far as is presently known is not fissionable. This element can cause a neutron loss in two ways. First, a neutron loss by 0Q the neutrons which Pa absorbs, and second, by formation of an element decaying into instead of into a known fissionable isotope. This effect however can be kept to a minimum by extracting the Pa from the slurry at sufficiently frequent intervals to reduce the ab-55 sorption by the Pa to about. 5 percent of the absorption by the thorium. 

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