Actinide behavior

Ray, I., and Thiele, H., Long Term Leaching of Silicate Systems Testing Procedure, Actinides Behavior and Mechanism, Karlsruhe Report KFK-2456 (1977). 

These quantities are both higher for experiment 4 and 5 than for the three experiments with unaltered repository components The loss of Pu through the core for experiments 1 and 2, for example, was 0 4 and 0 1 dpm/mL, respectively in experiments 4 and 5 the loss of Pu through the core appears to be 20 to 40 times greater This exercise is intended to show that there is no legitimate way to compare the behavior of altered and unaltered basalt from these data Experiment 6, yet to begin, should clarify this situation. What is clear from comparing the data in Table VI is that actinide behavior in altered and unaltered repository situations will be quite different ... 

Th02—ternary oxides or oxide phases with tetravalent americium are stabilized. The solid-state reaction of Am02 with most group V elements yields compounds with trivalent americium which are isostructural with the analogous rare earth compounds. In the last types of reactions americium exhibits a typical actinide behavior. 

Tanthanide chemistry is approaching its 200th Anniversary, but except for data on thorium and uranium the chemistry of the actinides is a comparative youngster of some 30 years. However, the two chemistries are intimately associated because their elements are of the f transition type and thus formally comparable with each other and different from other elements. Indeed, these parallels made it possible to unravel actinide behavior in the early days of transuranium element production. In addition to their chemical similarities, the two series also share the properties of magnetism and radiant energy absorption and emission characteristic of /-electron species. However, important differences exist also, particularly in oxidation states, in bonding, and in complex-ion formation. 

Performance assessment calculations of actinide speciation and solubility, and of the potential releases that could result if the repository is breached, were carried out as part of the CCA) for the waste isolation pilot plant (WIPP) (US DOE, 1996 US EPA, 1998a,b,c,d). The calculations modeled actinide behavior in a reference Salado brine and a less magnesium-rich brine from the Castile Formation as described previously (see Tables 6 and 8). The performance assessment calculations will be periodically repeated with updated parameter sets as part of site recertification. 

Molten Nitrate Salt Oxidation Process (10). The reaction of UO2 with molten nitrate salts to form uranates that are sub-sequently reduced to effect a separation of the uranium is being evaluated. The actinide behavior and uranate composition in equimolar sodium-potassium nitrate is being studied to determine the uranate stability and forecasting of cation behavior in subsequent process steps. 

The prediction phase is the part of waste management that is concerned with actinide behavior in the environment. It starts with the repository concept that emerges from the action phase and projects the capability of the repository and its surrounding geologic environment to keep the wastes isolated. 

For purposes of assessing the safety of repositories of radioactive wastes placed in geologic isolation, actinide behavior in the environment has been interpreted in terms of five steps of prediction ... 

The main objection against nuclear power is the risk of spread of "radioactivity" (radioactive elements) to the environment where it may cause health effects in humans. We have already discussed such effects (Ch. 18). Here, we are concerned with the chemical aspects of the sources of releases and of the migration of the radionuclides in the environment. Their chemical properties, together with hydrology, determine how fast they will move from their point of entry into the groundwater to water resources used by man this is schematically illustrated in Figure 22.1. In particular we discuss actinide behavior as these elements have the most hazardous radionuclides which may be released in the different steps of the nuclear fuel cycle, and, especially, from nuclear waste repositories. 

Hydrolysis is an inq)ortant factor in actinide behavior in natural waters as the pH is high enough to result in such reactions as ... 

This volume of the Handbook covers a variety of topics with three chapters dealing with a range of lanthanide magnetic materials, and three individual chapters concerning equiatomic ternary 3hterbium intermetallic compoimds, rare-earth polysulfides, and lanthanide organic complexes. Two of the chapters (206 and 210) also include information on the actinides and the comparative lanthanide/actinide behaviors. 

Normal lanthanide and actinide behavior versus heavy-electron behavior... 

One of the consequences of universality, well known from the study of phase transitions, is that systems with different microscopic Hamiltonians can have similar behaviors. This may be an important contributing factor to the observation that despite the basic difference between lanthanides and actinides (localized vs. delocalized electrons) the heavy-fermion behavior is similar. To the extent that this is so, pressure studies will not distinguish the two cases. Conversely, it is only to the extent that universality is violated, or is not expected, that we can expect to observe differences between itinerant and localized systems. Apart from deviations from scaling in measurements where universal behavior is expected, we will show from measurements of magnetic phase boundaries and of X-ray absorption spectra that differences between lanthanide and actinide behaviors are observable. 

Thus, a comparison of the lanthanide and actinide behavior under pressure can serve in the development of heuristic models and working hypotheses for future experimental studies, and can advance our understanding of changes in the electronic structure under pressure. 

Choppin, GR., and B.E. Stout. 1989. Actinide behavior in natural waters. Sci. Total Environ. 83 203-216. 

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