Nitrate waste forms

The densities of the final waste forms were 1.70 and 1.9 g/cm, and the compression strengths ranged from 1400 to 1900 psi (9.8-11.9 MPa) for both the chloride and nitrate waste forms. These values are significantly higher than the NRC land disposal requirement of 500 psi (3.5 MPa) for cement-based waste forms [17]. Thus, salt waste forms of the CBPC at high loadings are relatively dense hard materials that are suitable for salt waste... 

Applicabdity Limitations Photolysis is appropriate for difficult-to-treat chemicals (e.g., pesticides, dioxins, chlorinated organics), nitrated wastes, and those chemicals in media which permits photolyzing the waste. The waste matrix can often shield chemicals from the light (e.g., ultraviolet light absorbers, suspended solids, solid wastes). The photolysis process typically requires pretreatment to remove suspended materials, and the by-products formed may be more toxic than the parent molecules. 

The distillation process separates HNO3 from the U-bearlng HNO3-H2SO4. Similarly, HF can be recovered with the HNO3 if it is present in the initial solution. Because nitrates are mobile in the environment, their presence in a final waste form requires that more stringent performance criteria be used to ensure their immobilization. It is desirable to reduce both the volume and quantity of nitrates in the final waste stream discharged from the reclamation process. 

Extraction of tetrahedral pertechnetate anion from aqueous solutions using several crown ethers is well known. The coextraction of cesium (or strontium) and technetium from nuclear waste by calix[4]arene-crown-6 has been reported from alkaline media. Although technetium in its common pertechnetate form does not complex directly with crown ethers, pertechnetate extraction may be facilitated by crown ethers as the coanion of sodium (for alkaline nitrate waste). Pertechnetate at trace levels in the waste may be more than a 1000-fold more extractable than the smaller nitrate anion in ion-pair extraction processes.87... 

Mn VIS Mn compounds react with ammonium persulfate/silver nitrate to form permanganate, which is determined at 525 nm Applicable to 0.05-1.5 mg L-1 in natural and waste waters. Cl-, Br-, I-, and organic matter may interfere. 51... 

As may be seen from Table 17.8, Cs was added either as CsNOs or CsCl in the first three waste streams, whereas the form of Cs was not known in the last case, but certainly it was soluble because it was detected in wastewater. The TCLP results indicate that Cs, although added as nitrate or some other soluble form, is well immobilized. The LI is not as high as 18 that was reported by Bamba et al. [27] for a glass waste form, but it is certainly higher than the minimum of 6 expected from cement waste forms [28]. 

Singh et al. [33] patented a macroencapsulation technique in which waste forms are coated with a polymer for successful retention of Cl and NO3. This macroencapsulation of the waste forms reduced the nitrate leaching further in the ANS 16.1 test. Details may be found in Ref. [5]. 

Calcines are products obtained by removing the volatile components of the waste, i.e., water and nitrate, at temperatures between 400 and 900° C. The result is a mixture of oxides of fission products, actinides, and corrosion products in particulate form with a specific surface of 0.1 to 5 ra /g. The plain calcine is not very stable chemically because of its large surface area and the chemical properties of some of the oxides, and it is highly friable. To improve the properties of calcines, advanced forms are developed. One such product is the so-called multibarrier waste form, a composite consisting of calcine particles with inert coatings, such as pyrocarbon, silicon carbide, or aluminum, embedded in a metal matrix. Another advanced calcine is the so-called supercalcine. This is essentially a ceramic obtained by adding appropriate chemicals to the HLW to form refractory compounds of fission products and actinides when fired at 1200°C. Supercalcine requires consolidation by embedding in a matrix but does not need to be coated, as the material is supposed to have inherent chemical stability. 

Acetic anhydride and acetic acid increase the solubiUty of the two phases in each other, and they are employed for the commercial N-nitration of hexamethylenetetramine [100-97-0] (11) to form cyclotrimethylenetrinitramine [121-82-4] (RDX), (CH2)3(NN02)3. Renewed consideration has been given to replacing H2SO4 with an improved soHd catalyst to reduce the environmental problems of disposal or reconcentration of the waste acid and to increase production of desired nitrated isomers. For example, a catalyst with suitable pore size might increase the production of 4-MNT and reduce that of 3-MNT when toluene is nitrated. 

The plutonium extracted by the Purex process usually has been in the form of a concentrated nitrate solution or symp, which must be converted to anhydrous PuF [13842-83-6] or PuF, which are charge materials for metal production. The nitrate solution is sufficientiy pure for the processing to be conducted in gloveboxes without P- or y-shielding (130). The Pu is first precipitated as plutonium(IV) peroxide [12412-68-9], plutonium(Ill) oxalate [56609-10-0], plutonium(IV) oxalate [13278-81-4], or plutonium(Ill) fluoride. These precipitates are converted to anhydrous PuF or PuF. The precipitation process used depends on numerous factors, eg, derived purity of product, safety considerations, ease of recovering wastes, and required process equipment. The peroxide precipitation yields the purest product and generally is the preferred route (131). The peroxide precipitate is converted to PuF by HF—O2 gas or to PuF by HF—H2 gas (31,132). 

Vegetables are also a prime source of nitrate, and variations in their nitrate levels occur due to conditions employed during the cultivation and storage processes. The nitrate concentration in surface water has increased due to increased use of artificial fertilizers, changes in land use and disposal of waste from intensive fanning. Nitrate is readily converted in mammalian systems through bacterial and mammalian enzymes to nitrite which can react with amines, amides and amino acids to form NOC. 

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