An integrated method for the concentration and destruction of nitric acid-oxalic acid in plutonium oxalate precipitation mother liquor

Abstract

The invention provides a concentration and destroying integrated method for nitric acid and oxalic acid in plutonium oxalate sediment mother liquor. The concentration and destroying integrated method for the nitric acid and the oxalic acid in the plutonium oxalate sediment mother liquor comprises the following steps that (1) the reduction peak potential value of the nitric acid in the plutonium oxalate sediment mother liquor and the oxidation peak potential value of the oxalic acid in the plutonium oxalate sediment mother liquor are obtained through cyclic voltammetry; (2) a constant potential is selected within the crossed range of the obtained reduction peak potential value of the nitric acid and the obtained oxidation peak potential value of the oxalic acid; and (3) the plutonium oxalate sediment mother liquor is re-prepared and electrolyzed under the constant potential condition, and constant-temperature evaporation is conducted at the same time. The concentration and destroying integrated method for the nitric acid and the oxalic acid in the plutonium oxalate sediment mother liquor has the beneficial effects that concentration and destroying of the nitric acid and the oxalic acid in the plutonium oxalate sediment mother liquor are achieved through a one-step procedure, the operation method is simple, no external reagent is consumed, and generated waste liquid is reduced.

Description

technical field [0001] The invention relates to the technical field of spent fuel reprocessing, in particular to an integrated method for concentrating and destroying nitric acid-oxalic acid in plutonium oxalate precipitation mother liquor. Background technique [0002] In the spent fuel reprocessing process, oxalic acid is usually used as the precipitating agent for plutonium at the end of the plutonium product to realize plutonium oxalate precipitation, and the filtered solution is called plutonium oxalate precipitation mother liquor. In addition to about 0.05-0.1mol / L oxalic acid and 2-3mol / L nitric acid, the precipitation mother liquor also contains 50-200mg / L trace plutonium. In order to maximize the recovery of plutonium in the process, it is necessary to destroy the oxalic acid in the mother liquor and return it to the extraction process for further extraction and recovery of plutonium. [0003] Patent document CN 201010607410.X, the patent name is: a method for dest...

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Problems solved by technology

[0003] Patent document CN 201010607410.X, the patent name is: a method for destroying oxalic acid in the plutonium oxalate precipitation mother liquor, which discloses the use of a cyclically reversed DC power supply to electrolyze the plutonium oxalate precipitation mother liquor under constant voltage conditions. In the process of oxalic acid, the anode will produce reversible passivation, which avoids the generation of hydrogen at the anode and reduces the amount of hydrogen at the cathode. It is an efficient, fast and chemical-free electrolysis method to destroy the oxalic acid in the mother liquor. However, due to the low concentration of plutonium in the precipitation mother liquor, generally 50-100mgPu / L, if the precipitation mother liquor obtained by the electrolysis method is directly returned to the applied process flow, it will dilute the plutonium concentration in the plutonium purification feed solution and affect the extraction of plutonium Purification and concentration, the commonly used method is to increase the concentration of plutonium to the appropriate range required in the process by evaporation and concentration. However, in the process of evaporation and concentration, when the concentration of nitric acid in the solution is concentrated to a certain concentration, it is difficult to concentrate again. Therefore, it is urgent to develop In the process of electrolytic decomposition of oxalic acid, the combination of evaporation concentration and denitrification is used to achieve higher solution evaporation concentration multiples

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