Method for Producing Monophase Salts of Actinides and Device for Producing Same

Abstract

Method and device for the preparation of monophasic powders of actinide salts which are precursors in the production of fuel pellets. In one aspect, a compact and simple device is provided to obtain dry monophasic powders of actinide salts in one stage, while increasing the productivity, chemical and nuclear safety of the process. In a second aspect, the method comprises feeding of nitric actinides-containing solution and formic acid to a cylindrical healed reactor, grinding the resulting powder, and disc hanging the powder. The nitric actinides-containing solution and formic acid are continuously metered to the upper zone of the reactor so that the reactive chemicals are mixed in a thin film on the heat-exchange surface, where the reaction mixture is continuously stirred by rotor blades. Also occurring are the processes of denitration, formation of the relevant compounds, their drying and grinding and collecting dry salts of actinides in a hopper by gravity.

Claims

1. A method for producing monophase powders of actinide salts, comprising feeding of nitric actinides-containing solution and formic acid in the cylindrical heated reactor, grinding the resulting powder, its discharge, characterized in that nitric actinides-containing solution and formic acid are continuously metered to the upper zone of the reactor, thus the reactive chemicals are mixed in a thin film on the heat-exchange surface, where the reaction mixture is continuously stirred by the rotor blades, while sequentially the processes of denitration, formation of the relevant compounds, their drying and grinding and collecting dry salts of actinides in a hopper by gravity.

2. The method according to claim 1 characterized in that the actinide-containing solution and formic acid are batched separately and continuously in a molar ratio of nitrate ion and formate ion (1:4.3) (1:4.5);

3. The method according to claim 1 characterized in that the heat exchange surface temperature is maintained at 140±5° C.

4. A device for producing monophasic powders of actinide salts, including a vertical rotary-film reactor equipped with a heater, chokers for entering reactive chemicals and for removing the vapor-gas phase, inside which is a rotor made with the possibility of rotation, with blades fixed along its entire length, characterized in that the choke for the reactive chemicals entering is made in the form of a tee, and the receiving hopper is made with the possibility of joining to the reactor vessel and is equipped with a heater.

5. The device according to claim 4 characterized in that the rotor is made welded with four blades, and the gap between the blade edge and the wall is 0.5-1.5 mm.

6. The device according to claim 4 characterized in that the tee flow choke for the supply of solutions and a choke for the discharge of the outgoing vapor-gas mixture are located in the upper part of the reactor above the edge of the blades.

Description

EXAMPLE 1

[0027] Solutions of uranyl nitrate in 1 molar HNO.sub.3 with the uranium concentration of 100 g/l and concentrated formic acid at room temperature are fed separately to the reactor using metering pumps through a tee flow choke, while the molar ratio of nitrate-ion/formic acid is 1:3.6. The temperature on the reactor wall is 142° C., and the temperature on the receiving hopper wall is 145° C. The powder was poured into the receiving hopper homogeneously. According to XRF data, the powder consists of two crystalline phases: 50 wt. % of hydrate formate (CH.sub.2O.sub.5U) and 50 wt. % of aqueous formate (C.sub.2H.sub.2O.sub.6U.H.sub.2O). The X-ray diffraction pattern of the powder obtained by Example 1 is shown in FIG. 2, where: .circle-solid. is a compound with the CH.sub.2O.sub.5U; structure; .square-solid. is a compound with the C.sub.2H.sub.2O.sub.6U.H.sub.2O structure.

EXAMPLE 2

[0028] Solutions of uranyl nitrate in 1 molar HNO.sub.3 with the uranium concentration of 100 g/l and concentrated formic acid at room temperature are fed separately to the reactor using metering pumps through a tee flow choke, while the molar ratio of nitrate-ion/formic acid is 1:4.0. The temperature on the reactor wall is 140° C., and the temperature on the receiving hopper wall is 130° C. The powder was poured into the receiving hopper homogeneously. According to XRF data, the powder consists of two crystalline phases: 20 wt. % of hydrate formate (CH.sub.2O.sub.5U) and 80 wt. % of aqueous formate (C.sub.2H.sub.2O.sub.6U.H.sub.2O). The X-ray diffraction pattern of the powder obtained by Example 2 is shown in FIG. 3, where: .circle-solid. is a compound with the CH.sub.2O.sub.5U; structure; .square-solid. is a compound with the C.sub.2H.sub.2O.sub.6U.H.sub.2O structure.

EXAMPLE 3

[0029] Solutions of uranyl nitrate in 1 molar HNO.sub.3 with the uranium concentration of 100 g/l and concentrated formic acid at room temperature are fed separately to the reactor using metering pumps through a tee flow choke, while the molar ratio of nitrate-ion/formic acid is 1:4.3. The temperature on the reactor wall is 142° C., and the temperature on the receiving hopper wall is 160° C. The powder was poured into the receiving hopper homogeneously. According to the XRF data, the monophasic powder consists of 100 mass. % of aqueous formate (C.sub.2H.sub.2O.sub.6U.H.sub.2O). The X-ray diffraction pattern of the powder obtained by Example 3 is shown in FIG. 4, where: .square-solid. is a compound with the structure of C.sub.2H.sub.2O.sub.6U.H.sub.2O.

EXAMPLE 4

[0030] Nitric acid solution in 0.845 molar HNO.sub.3 with a concentration of 91.1 g/l for uranium, 9.0 g/l for thorium, and concentrated formic acid at room temperature is fed separately to the reactor using metering pumps through a tee flow choke, while the molar ratio of nitrate-ion/formic acid is 1:4.5. The temperature on the reactor wall is 142° C., and the temperature on the receiving hopper wall is 160° C. The powder was poured into the receiving hopper homogeneously, and according to the XRF data comprised a compound with the structure of aqueous formate and the formula of (C.sub.2H.sub.2O.sub.6(U, Th).H.sub.2O). The X-ray diffraction pattern of the powder obtained by Example 4 is shown in FIG. 5, where: .square-solid. is a compound with the structure of C.sub.2H.sub.2O.sub.6U.H.sub.2O.