Waste nitric acid, composition

Our research program at Rocky Flats has been aimed at reducing the levels of americium and plutonium In the nitric acid waste which arises from the anion exchange purification of plutonium. These wastes currently contain TRU or transuranlc elements to such a concentration that the waste must be stored In a geological repository after neutralization and flocculant precipitation. Table I shows the average composition of the w ste. 

The temperature of the gases leaving the oxidiser is reduced in a waste-heat boiler and cooler-condenser. There will be no separation of material in the WHB but the composition will change, as NO is oxidised to NO2 as the temperature falls. The amount oxidised will depend on the residence time and temperature (see Stephenson). The oxidation is essentially complete at the cooler-condenser outlet. The water in the gas condenses in the cooler-condenser to form dilute nitric acid, 40 to 50 per cent w/w. 

There are four main applications of the SCR-NH3 process for the reduction of NO in the emissions (1) power plants, (2) gas turbines, (3) waste incineration and (4) nitric acid plants. Although, often, specific distinction is not made between these cases and the same catalysts are assumed to be applicable in all cases, there are significant differences in terms of composition of the emissions and space velocities. A specific difference between the first three cases (combustion) and the latter (nitric acid plants) regards NO/N02 ratio which is typically close to 20 for combustion processes and close to 1 for the nitric acid plants. Furthermore, no S02 is present in the latter case. 

After the cotton has been removed from the nitration tank (Fig. 135) the composition of the acid in the tank is adjusted so that in quantity and strength of it remains unchanged throughout. The waste acid from the centrifuge is low in nitric acid. The regeneration of this spent acid by addition of oleum and fresh nitric acid is uneconomic. Spent acid is denitrated. 

During plutonium reconversion in a reprocessing plant, oxalate supernatant is normally generated during plutonium precipitation by oxalic acid as plutonium oxalate. This is further converted into plutonium oxide. This waste solution will have the following composition uranium (U) 5 gm dm , plutonium (Pu) 25 mg dm, mthenium (Ru ° ) 0.0032 mCi dm, cesium (Cs ) 0.003 mCi dm , nitric acid 3 M, and H2C2O4 0.1 M. 

Waste Compositions Selected for Study in the WFP. The major source of high-level wastes is the raflBnate or aqueous waste stream from the first cycle of the Purex solvent extraction process. The stream is a nitric acid solution containing over 99.9% of the nonvolatile fission... 

In this example, uranium and ruthenium are the key components whose compositions in feed, aqueous waste, and organic extract are specified. Nitric acid concentration in feed is specified, but its distribution between the two product streams must be found by trial, as in the zirconium-hafnium separation example in Sec. 6.5 of Chap. 4. The HNO3 concentrations of 0.02 M in organic extract and 1.658 M in aqueous waste were found by trial to require the same number of scrubbing and extracting stages as the specified uranium and zirconium separation, as will now be shown, and hence represent the calculated distribution of nitric acid. 

In a study of residential exposure to Cr-laden wastes in Hudson County, New Jersey, Lioy etal., 1992) collected 3-day and 4-day composite samples using low-volume air samplers equipped with 37-mm Teflon filters. Total Cr in airborne particles was determined using XRF with a detection limit of 2 pg g (shown in Table 11.3), and extractable Cr (not shown) was determined using nitric acid/sulfiiric acid digestion and ICP-AES. The mean ratio of extractable Cr to total Cr was 0.3. 

Analysis of explosives, 197. acetone, 209. blasting gelatine, 199. cap composition, 241. cordite, 206. celluloid, 230. dynamite, 197. forcite, 202. fulminate, 240. glycerine, 233. gun-cotton, 212. nitric acid, 24. picric acid, 230. tonite, 205. waste acids, 239. 

Table I. Composition of Rocky Flats Waste Nitric Acid...

The question of absorption of adds from their mixtures has been studied experimentally by Demougin and Bonnet [28], by Wilson and Miles [13] and more recently by Chedin [11]. The last author has provided clear experimental evidence that the nitric add remaining in nitrocellulose after nitration has ended is present in two forms as spent add (after-nitration add) of the same composition as the waste add, and as nitric add diluted to varying concentration by the water absorbed by the nitrocellulose fibres. The spent add can be removed to some extent from the nitrocotton by squeezing it between rollers. By increasing the pressure from 150 to 550 kg/cm2 the residue of this acid can be reduced from 121 to 45%. The chemical composition of the add removed does not change appreciably with the wringing pressure. Nitric add absorbed by nitrocellulose cannot be removed by mechanical operations such as, for instance, hydro-extraction. 

On the basis of experience using the ceramic melters and present developments in this field, the present feasibility of Russian Pu-containing materials is assessed. Rich Pu wastes from the radiochemical and chemical-metallurgical production of plutonium are included in this category of wastes for example, hard-to-dissolve residues after treatment by a mixture of nitric and fluoride acids. These wastes have a complicated chemical composition (Table 3). 

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