Nitric-acid raffinates produced during extractive reprocessing of spent nuclear fuel are ordinarily evaporated and nitric acid is recovered from the liquor vapors, obtained during evaporation, by rectification [1]. Raffinates can contain organic substances, which end up in them as a result of dissolution and removal of the extracting agent and technological additives (as complexing agents and reducing agents). Ordinarily, under conditions of evaporation of raffinates organic substances interact with nitric acid, and some of them are simultaneously distilled off with the liquor vapor, which could influence the technological regimes and the quality of the products of the evaporation and rectification operations. For this reason, it is of practical interest to investigate the behavior of organic substances under conditions of evaporation of raffinates. The results of such investigations reported in this paper supplement existing results (see, for example, [2-4]) or are published for the first time.We determined the kinetics of the interaction of organic substances with nitric acid in water solutions. The concentration regions studied are determined by technological necessity. The investigations were performed in a glass vessel with a reflux cooler and electrical heating of the walls. A vacuum system was connected to the cooler in order to maintain a prescribed boiling point of the solution and to a system of flasks filled with saturated NaCI solution for the purpose of measuring the volume of the gases released, with NaOH solutions for absorption of the acid gases (CO 2 and NO2), and with hydrogen peroxide for absorption of NO. The concentration of nitric acid was determined by alkalimetric titration and that of the organic substances was determined by the standard methods.Interaction of Lactic and Nitric Acids. The acid concentration was determined by potentiometric titration with an alkali in water medium [5] and in acetone [6]. It follows from Table I that the interaction of nitric and lactic acids is noticeable with an initial concentration of the former (X o) of 3.44 moles/liter. It intensifies with increasing X o and m o (it was determined that Mn 2 + and Fe 3 + also increase the interaction rate). The reaction terminates approximately after 4 h (X and m become constants). To identify the organic matter remaining after completion of the reaction, a portion of the solution was distilled off. This yielded condensates which were analyzed to determine the equilibrium distribution of organic material contained in them between the liquid and vapor (equilibrium was determined by the method of [7]). The composition of the condensates fell into the range X = 0.5-1.4 moles/liter and m = 0.2-0.3 moles/liter. At atmospheric pressure the distribution factor of the organic matter between the vapor and the liquid was equal to 0.6-1, which was close to the distribution factor of the acetic acid determined under the same conditions. The presence of traces of acetic acid in the condensates was confirmed by qualitative analysis...

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At the present time vitrification is the main method of localization of high-level liquid wastes. The high-level liquid wastes which are to be vitrified and which are obtained by extraction recovery of nuclear fuel from BBI~R and research reactors can be represented in the form of the system HNO 3 --H20 --NaNO 3 --AI(NO3)yTo obtain phosphate glass phosphoric acid is added [1] and correspondingly we obtain the system HNO3 _ H20 _ NaNO 3 _ AI(NO3)3 m H3PO4.Ordinarily, high-level solutions are relatively dilute. Therefore to decrease the water load on the vitrification apparatus and to increase its glass capacity the solutions are first concentrated by evaporation. The degree of evaporation is determined by the ratio of the salt concentration in the evaporated solution to the concentration in the initial solution and the degree of concentration is determined as the ratio of the salt concentration in the solution entering the vitrification apparatus to the initial concentration. The degrees of evaporation and concentration may or may not be equal to one another. The degree of evaporation (concentration) is determined by the solubility of the salts. In the process of evaporation the volatile components (nitric acid and water) are driven off, i.e., denitration of the solution occurs. Therefore, the data on the solubility and liquid-vapor equilibrium in the indicated nitric-acid (1), nitric-phosphoric-acid salt systems (2), and in their component subsystems form the physical-chemical basis of the processes of evaporation and denitration of high-level wastes.In the present paper we present additional data or data not available in the scientific-technical literature.The experimental results are presented in Tables 1-9, where the concentration of nitrates and phosphoric acid is given in mass %, the concentration of free nitric acid is given in mass % relative to the sum of the water and nitric acid, and the concentration of bound nitric acid is expressed in terms of the nitric acid deficit in %, relative to the acid that should be bound in sodium and aluminum nitrates, with a minus sign.Data on the Solubility. It is well known that the solubility of sodium and aluminum nitrates decreases with increasing nitric acid concentration [5] and the solubility of sodium nitrates decreases with the addition of phosphoric acid [6]. The data obtained with constant ratios of the nitrates and phosphoric acid, which is observed in the vitrification technology [1], and at a temperature higher than in [5,6], specifically, at the boiling point at atmospheric pressure, are presented in Tables 1-3. These data determine the maximum degree of evaporation.As one can see from Tables 1 and 2, as phosphoric acid is added and its concentration increases, the solubility of sodium nitrate decreases (in agreement with [6]) and the solubility of aluminum nitrate also decreases. The solubility of aluminum nitrate, just as the mixture of sodium and aluminum nitrates, in the presence of phosphoric acid [the system (2)] increases as the nitric acid concent...