Reaction with actinides

The compositions of the most numerous actinide compounds with elements of the group V of the periodic table (X = N, P, As, Sb, Bi) belong to the types AnX2, An3Xt, AnX. These pnictides can be synthesized in solid-gas-reactions with actinide hydride, or with metal powder obtained by thermal dissociation of hydrides. 

The effect of Coulomb repulsion on the cross section starts to act severely for fusion reactions to produce elements beyond fermium. From there on a continuous decrease of cross section was measured from microbams for the synthesis of nobelium down to picobarns for the synthesis of element 112. Data obtained in reactions with Pb and Bi for the In-evaporation channel at low excitation energies of about 10-15 MeV (therefore named cold fusion) and in reactions with actinide targets at excitation energies of 35-45 MeV (hot fusion) for the 4n channel are plotted in Figure 7a and b, respectively. 

Fig. 7. Measured cross sections (a) for reactions with 208Pb and 209Bi targets and In evaporation and (b) for reactions with actinide targets and 4n evaporation. At the right ordinate cold fusion reaction yields are given which are obtained with the presently available technology. The values (N-Z)/2 denote the projectile isospin.

Both arsonic and arsinic acids give precipitates with many metal ions, a property which has found considerable use in analytical chemistry. Of particular importance are certain a2o dyes (qv) containing both arsonic and sulfonic acid groups which give specific color reactions with a wide variety of transition, lanthanide, and actinide metal ions. One of the best known of these dyes is... 

The chemical similarity between lanthanide and actinide metals suggests that C2H I2 might also react with actinide metals. Preliminary experiments found no reaction between thorium or uranium metals and a THF solution of Plutonium and neptunium... 

Ames, L.L. Rai, D. Serne, R.J. "A Review of Actinide-Sediment Reactions with Annotated Bibliography" BNWL-1983 Battelle Northwest Lab. Richland, 1976. 

The overall distribution of lanthanides in bone may be influenced by the reactions between trivalent cations and bone surfaces. Bone surfaces accumulate many poorly utilized or excreted cations present in the circulation. The mechanisms of accumulation in bone may include reactions with bone mineral such as adsorption, ion exchange, and ionic bond formation (Neuman and Neuman, 1958) as well as the formation of complexes with proteins or other organic bone constituents (Taylor, 1972). The uptake of lanthanides and actinides by bone mineral appears to be independent of the ionic radius. Taylor et al. (1971) have shown that the in vitro uptakes on powdered bone ash of 241Am(III) (ionic radius 0.98 A) and of 239Pu(IV) (ionic radius 0.90 A) were 0.97 0.016 and 0.98 0.007, respectively. In vitro experiments by Foreman (1962) suggested that Pu(IV) accumulated on powdered bone or bone ash by adsorption, a relatively nonspecific reaction. On the other hand, reactions with organic bone constituents appear to depend on ionic radius. The complexes of the smaller Pu(IV) ion and any of the organic bone constituents tested thus far were more stable (as determined by gel filtration) than the complexes with Am(III) or Cm(III) (Taylor, 1972). 

Excellent quality metal, comparable to that from the halide reduction, can be prepared by this technique. A big advantage is that no neutrons are present from (a,ra) reactions on fluorine nuclei, in marked contrast to the case with actinide fluorides. 

As many physical properties of the actinide metals depend significantly on the sample purity, refining of the metals is mandatory. The choice of the refining methods is determined by the chemical reactivity of the actinide metal in the presence of the constituents of air, by high temperature reactions with crucible materials, by the specific radioactivity and the availability of the actinide elements. 

The chalcogenides are synthesized either by reaction of the chalcogen vapour with the actinide metal or the hydride (Faraday-method), or in reaction with compounds ... 

Therefore, and to avoid possible reactions with the quartz wall, it was attempted to combine synthesis and crystal growth of actinide pnictides in a modified van Arkel process Actinide metal or carbide - the latter obtained by carboreduction of the oxide - are heated in the presence of the pnictogen and of the transporting agent at the... 

In the work reported here, which was directed toward the attainment of an isotopic enrichment of the trivalent actinide and lanthanide elements, the problem was compounded by the fact that these elements do not readily form appropriate compounds, like iodine in ethyl iodide. They do form some stable organic chelates, and, indeed, it is possible to obtain a Szilard-Chalmers reaction with such compounds. However, their radiation damage resistance does not appear adequate to permit useful production of an isotope like 247Cm, which requires a thermal neutron exposure ap-... 

As a chemical group, toxicity of nitndes generally stems from the possible reactions with water to form toxic fumes (especially ammonia) rather than from the nitride. There are, of course, exceptions Fine powder or dust of the nitndes of the transition metals can be pyrophoric nitrides of the actinide metals are carcinogenic. 

Also present in many natural waters are humic/fulvic acid, citric acid, and the like. These organics also can complex actinides. In Figure 15.18, we show the relative stability constants for the first complexation reaction of various ligands with actinides of different oxidation states. Clearly, the carbonate and humate ions along with hydrolysis dominate the chemistry. The tetravalent actinide ions will tend toward hydrolysis reactions or carbonate complexation rather than humate/fulvate formation. 

A single oxo bridge may subtend an angle between 140° and 180°, this angle being determined by steric or electronic factors (Table 3).95 103 Almost all these examples refer to the solid state, but there are also several homo- and hetero-nuclear M—O—M and M—O—M—O—M species known in solution. Often these are intermediates in, or products of, electron transfer reactions with oxide-bridging inner-sphere mechanisms. Examples include V—O—V in V(aq)2+ reduction of VO(aq)2+, and Act—O—Cr in Cr(aq)2+ reduction of UOj+ or PuOj+ a useful and extensive list of such species has been compiled. Tlie most recent examples are another V—O—V unit, this time from VO(aq)2+ and VOJ,105 and an all-actinide species containing neptunium(VI) and uranium-(VI).106 An example of a trinuclear anion of this type, with the metal in two oxidation states, is provided by (31).107... 

Hydrolysis reactions are common to all actinide ions in nearneutral solutions, and take place either in parallel with or predominantly over other complexation reactions. In connection with the migration studies of actinide ions in natural waters, attention recently has been focused on hydrolysis reactions of actinides since these reactions are important in determining the solubility of the actinide hydroxide or oxide. Although numerous studies have been made (1-4) to determine stability constants of various hydrolysis products, much of the necessary data are still lacking. The acquisition of these data and further improvement or verification of the existing data is desirable. 

---