Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Fission product solubility

Element uptake from soil and transfer into the edible parts of plants have been addressed in several other studies. Soil-to-plant transfer factors in fruit and vegetables grown in various agricultural conditions have been determined for, for example, Pt [100], T1 [101], and various other metal contaminants [102], In a study on stable isotopes of fission product elements (Ce, Cs, Sr), an in vitro enzy-molysis method has been applied to investigate the solubilization of the analytes from fodder in a simulated ruminant digestion [103], The effect of inhibitors of fission product solubility was also considered and essential elements were determined simultaneously to evaluate potential nutrition problems for the animals from the use of such inhibitors. Selective leaching of individual classes of metal complexes with different ligands and sequential enzymolysis have been recently applied to estimate the potential bioavailability to humans of Cd and Pb in cocoa powder and related products [104]. [Pg.253]

Uranium Purification. Subsequent uranium cycles provide additional separation from residual plutonium and fission products, particularly zirconium— niobium and mthenium (30). This is accompHshed by repeating the extraction/stripping cycle. Decontamination factors greater than 10 at losses of less than 0.1 wt % are routinely attainable. However, mthenium can exist in several valence states simultaneously and can form several nitrosyl—nitrate complexes, some for which are extracted readily by TBP. Under certain conditions, the nitrates of zirconium and niobium form soluble compounds or hydrous coUoids that compHcate the Hquid—Hquid extraction. SiUca-gel adsorption or one of the similar Hquid—soHd techniques may also be used to further purify the product streams. [Pg.206]

The primary issue is to prevent groundwater from becoming radioactively contaminated. Thus, the property of concern of the long-lived radioactive species is their solubility in water. The long-lived actinides such as plutonium are metallic and insoluble even if water were to penetrate into the repository. Certain fission-product isotopes such as iodine-129 and technicium-99 are soluble, however, and therefore represent the principal although very low level hazard. Studies of Yucca Mountain, Nevada, tentatively chosen as the site for the spent fuel and high level waste repository, are underway (44). [Pg.242]

Three classes of carbamoylmethylphosphoryl extractants were studied for their ability to extract selected tri-, tetra-, and hexavalent actinides from nitric acid. The three extractants are dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP), hexyl hexyl-N,N-diethylcarbamoylmethylphosphinate (HHDECMP), and octyl(phenyl)-N,N-diisobutylcarbamoylmethylphos-phine oxide 0< >D[IB]CMP0. The above three extrac-trants were compared on the basis of nitric acid and extractant dependencies for Am(III), solubility of complexes on loading with Nd(III) and U(VI), and selectivity of actinide(III) over fission products. [Pg.428]

We have studied the extractant behavior of a series of compounds containing the carbamoylmethylphosphoryl (CMP) moiety in which the basicity of the phosphoryl group and the steric bulk of the substituent group are varied (10,LL). These studies have led to the development of extractants which have combinations of substituent groups that impart to the resultant molecule improved ability to extract Am(III) from nitric acid and to withstand hydrolytic degradation. At the same time good selectivity of actinides over most fission products and favorable solubility properties on actinide loading are maintained (11). [Pg.429]

For the rapid determination of Tc in a mixture of uranium fission products. Love and Greendale have used the method of amalgam polarography. It consists in a selective reduction of technetium at a dropping mercury electrode at a potential of —1.55 V vs. SCE in a medium of 1 M sodium citrate and 0.1 M NaOH. Under these conditions, technetium is reduced to an oxidation state which is soluble in mercury. The amalgam is removed from the solution of fission fragments and the amount of Tc determined in nitric acid solution of the amalgam by a y count. For Tc the measurement accuracy is within 1 %, and the decontamination factor from other fission products 10 . [Pg.143]

Since the water movement will be very slow compared with the rate at which the wastes dissolve, we are concerned first and foremost with equilibrium solubility. Also, if only to relate behaviour on the geological time scale to that on the laboratory time scale, we will need to know about the mechanisms and kinetics of dissolution and leaching. The waste forms envisaged at present are glass blocks containing separated fission products and residual actinides fused into the glass and, alternatively, the uranium dioxide matrix of the used fuel containing unseparated fission products and plutonium. In the... [Pg.337]

Because of their similarity to the composition of human bile, which consists mainly of bile salts, phospholipids, and cholesterol, of interest for pharmaceutical studies are mainly binary bile salt micelles (BS/PL) (32,33). The function of the bile is to emulsify lipids in food and to dissolve the fission products of lipids as well as fat-soluble vitamins. The spontaneous formation of micelles is a necessary prerequisite to a contact of the lipophilic fission products with the intestinal wall. For affinity measurements, micellar sys-... [Pg.126]

The dissolution time for the unreprocessed fuel would be at least 1 million years due to the limited water supply, even if a rapid oxidation of uranium to the hexavalent state and a subse-guent formation of water soluble carbonate complexes are assumed (15). Since the conditions are reducing in the groundwater (see beTow) the dissolution time would probably be several orders of magnitude larger. The unsignificant dissolution of uranium and fission products observed in the Oklo-deposit (16) is an example of a similar extremely slow leaching process in the natural environment. [Pg.51]

The most important chemical parameter affecting the deposition and subsequent mobility of radioactive aerosols, such as the nuclides 90Sr and 137Cs examined in this study, is their solubility in rainwater. If these aerosols are dissolved in precipitation, the main factor in their transport is the movement of the rainwater, not the transport of insoluble aerosol particles. Huff and Kruger (2) examined the solubility products of strontium and chemically similar compounds which may carry trace amounts of 90Sr, and they estimated that strontium should be soluble in precipitation. Solubility tables also indicate that cesium compounds likely to exist in precipitation should be soluble. It was noted that the possibility did exist that some of the fission product "Sr and 137Cs might be bound within the structure of insoluble natural aerosols or nuclear weapon debris. [Pg.498]

Since the pioneering work of Siddall, /V./V-dialkyl amides have been evaluated extensively as alternative extractants to TBP (200, 201). The salient features of amides as extractants are (i) low volume of secondary waste generated (completely incinerable), (ii) innocuous nature of chemical and radiolytic degradation products (better decontamination from fission products andregeneration/clean up easier), (iii) low aqueous-phase solubility, (iv) final U and Pu products streams are free of P contamination, and (v) ease of synthesis. However, LOC values of U and Pu as well as viscosity are... [Pg.93]

The major drawback of phenyl derivatives of BNOPCs is that they are only scarcely soluble in classical hydrocarbon diluents without the addition of massive amounts of phase modifiers, such as TBP or TOPO. They are, however, soluble in halogenated and nitro-halogenated organic diluents (130). Furthermore, the anomalous aryl strengthening effect also increases the extraction of other fission products, such as Zr, Mo, Tc, and Fe, which can only be avoided by introducing specific hydrophilic complexants (e.g., acetohydroxamic acid). [Pg.142]

The ZEALEX Process Researchers from KRI have shown that the zirconium salt of dibutyl phosphoric acid (ZS-HDBP) was soluble in Isopar-L in the presence of 30% TBP. This super PUREX solvent, known as ZEALEX, extracts actinides (Np-Am) together with lanthanides and other fission products, such as Ba, Cs, Fe, Mo, and Sr from nitric acid solutions. The extraction yields depend on both the molar ratio between Zr and HDBP in the 30% TBP/Isopar-L mixture and the concentration of HN03 (232). Trivalent transplutonium and lanthanide elements can be stripped together from the loaded ZEALEX solvent by a complexing solution, mixing ammonium carbonate, (NH4)2C03, and ethylenediamine-N.N.N. N -tetraacetic acid (EDTA). An optimized version of the process should allow the separation of... [Pg.165]

There is virtually no contact between the primary circuit medium and coolant in case of the first-type cracks. During operation only gaseous and volatile fission products could be released via such cracks to the primary circuit medium. The second-type cracks could cause fuel corrosion and washing out of soluble fission products (cesiiun, strontium) and fuel particles to the coolant circuit. [Pg.250]

Some hazardous metals such as chromium (Cr) and radioactive fission products such as technetium (Tc) exhibit exactly opposite solubility characteristics as compared to the metals discussed above. These metals in higher oxidation states, e.g., chromates (Cr ) and pertechnetate (Tc ), are more soluble than their counterparts, e.g., chromium and technetium oxide (Cr and Tc " "). Chromium is a hazardous metal and technetium ( Tc) is a radioactive isotope. As we shall see in Chapters 16 and 17, one way to reduce their dispersibility is to reduce their solubility in ground water and reduce them into their lower oxidation state, and then encapsulate them in the phosphate ceramic. Thus, the reduction approach is also useful in stabilization of hazardous metal oxides of high oxidation states. Because of these reasons, a good understanding of the reduction mechanism of oxides... [Pg.75]


See other pages where Fission product solubility is mentioned: [Pg.37]    [Pg.725]    [Pg.37]    [Pg.725]    [Pg.242]    [Pg.1097]    [Pg.1257]    [Pg.22]    [Pg.431]    [Pg.444]    [Pg.11]    [Pg.7]    [Pg.548]    [Pg.622]    [Pg.272]    [Pg.66]    [Pg.125]    [Pg.561]    [Pg.457]    [Pg.1106]    [Pg.467]    [Pg.945]    [Pg.89]    [Pg.197]    [Pg.362]    [Pg.525]    [Pg.355]    [Pg.146]    [Pg.159]    [Pg.454]    [Pg.16]    [Pg.436]    [Pg.448]    [Pg.449]   
See also in sourсe #XX -- [ Pg.725 ]




SEARCH



Fission products

Fission solubilities

Products soluble

Solubility products

Soluble fission products, discussion

© 2024 chempedia.info