RU2294314C2 - Device for separation of radioactive elements possessing different ability for forming amalgams - Google Patents

Abstract

FIELD: separation and high cleaning of radioactive elements possessing ability for forming amalgams; radio-chemical industry for extraction of radioactive isotopes for medicine and analytical chemistry.

SUBSTANCE: proposed device has semi-counterflow unit for separation of radioactive elements possessing different ability for forming amalgams by cementation of one of elements, electrolysis, separation and regeneration cells located vertically one above another and provided with mixers mounted on common shaft, reservoir for receiving regenerated mercury and screw feeder tightly fitted in tube and rotating together with it; mercury flows from cell to cell through hydraulic seal by gravity.

EFFECT: operation of remotely controlled device in radiation shielded chambers.

2 cl, 1 dwg

Description

The invention relates to a device for the separation and deep cleaning of radioactive elements with different ability to form amalgams, and may find application in the radiochemical industry for the separation of radioactive isotopes used in medicine, in analytical chemistry for the isolation of the analyzed element.

There are many types of amalgam reactors of batch or continuous operation (V. A. Smirnov. “Amalgam Restoration”, “Chemistry” Publishing House, Leningrad Branch, 1970, pp. 49-54). Industrial reactors are not suitable for the separation of radioactive elements because of their large size and the inability to remotely control their operation in radiation-protective chambers.

Closest to the claimed is a device with continuous regeneration of amalgam (ibid., P. 51). It consists of a mold filled with a layer of mercury 1 cm thick. On top of the mercury is covered with a glass bell, which is mounted on supports to create a gap between its lower edge and the bottom of the mold in 1-2 mm. A 40% alkali solution is poured into the outer annular space into which the nickel anode is placed. The cathode is mercury. The amalgam formed during electrolysis is carried away into the internal space of the device, where it is in contact with the solution of the recovered substance loaded into it.

This device is simple in design, it is a closed system. But it has a number of significant drawbacks:

- the inability to control the concentration of amalgam in the reaction space;

- the inability to operate the installation in conditions of radiation-protective chambers.

The task of the present invention is to provide a remotely controlled device operating in conditions of radiation-protective chambers for the separation of radioactive elements and obtain radiochemically pure preparations.

To solve this problem, a semi-countercurrent device is proposed for the separation of radioactive elements with different ability to form amalgams by cementing one of the elements, containing electrolysis, separation and regeneration cells located vertically one below the other, equipped with mixers located on one shaft, a collection tank regenerated mercury and a transporting screw tightly planted in the pipe and rotating together with the pipe, the cathode in the electrolysis cell being Tut, a platinum anode ring at the top of the electrolytic cell and the mercury moves from cell to cell through hydraulic locks by gravity.

The device for the separation of radioactive elements with different ability to form amalgams, shown in the drawing, consists of an electrolysis cell 1, a separation cell 2, regeneration cells 3, a container for collecting mercury 4, a conveying screw 5, a screw drive 6, an agitator 7, with an electric drive 8 and hydraulic locks 9.

Separation and electrolysis cells are made of plexiglass, regeneration cells are made of stainless steel.

The block layout of the device allows you to send the device into the radiation-protective chamber disassembled (in blocks) through the conveyor, assemble and serve with copy manipulators.

The heavy phase (mercury) moves from cell to cell from top to bottom under the influence of gravity.

The formation of sodium amalgam occurs in the electrolysis cell under the influence of an electric current. The anode is a platinum ring, located in a solution of sodium alkali, constantly flowing through the cell, mercury is the cathode. Dosing of mercury into the electrolysis cell is carried out by a conveying screw, tightly fitted into the pipe (5) and rotating together with the pipe using a separate drive (6). When the screw rotates, mercury rises along the helical groove and enters the electrolysis cell. The concentration of the resulting amalgam in the cell is controlled by the speed of rotation of the screw and the current strength.

Amalgam of sodium of a given concentration from the electrolysis cell flows through a water trap into the separation cell located under the electrolysis. An aqueous solution of separable elements of such a composition, in which sodium amalgam restores only one element, leaving the other in ionic form, is poured into the separation cell. The amalgam formed as a result of this process enters through the water trap into the regenerating cells located under the separation cell.

From the regeneration cells, the purified mercury enters the mercury collector (4) and then auger into the electrolysis cell.

Thus, an element with a greater ability to form an amalgam is removed from the system with a regenerating solution into a separate fraction. The second shared element remains in the stationary aqueous phase in the separation cell and is removed from it at the end of the process.

Distinctive features of the proposed solution is:

The vertical arrangement of the unit cells, allowing the use of gravity to move mercury through the cells and one drive to rotate the mixers in all the cells.

Use for the return and dosing of mercury into the electrolysis cell of the screw with an adjustable rotation speed, which allows you to set the required concentration of sodium amalgam and reuse mercury.

Semi-countercurrent mode of the process, which allows the separation of elements, removing one of the nickname from the separation cell with mercury in the form of an amalgam, leaving the other in an aqueous solution.

The block design of the installation units, allowing remote maintenance of the installation in conditions of radiation-protective chambers

Usage example

Obtaining the drug gadolinium-153.

Gadolinium-153 is obtained by irradiating natural europium in a nuclear reactor by the reaction (n, γ). In the irradiated material, the γ activity of the Gd-153 isotope is 15–20% of the total γ activity. For use in nuclear medicine, the gadolinium-153 preparation should contain γ-impurities of not more than 7 · 10 ^-4 %.

A target with a starting load of natural europium 9 g (for metal) after irradiation in the reactor and holding in the pool was dissolved and analyzed. The solution contained 1080 Ci of europium isotopes and 110 Ci of gadolinium-153, which corresponded to ~ 1 g of gadolinium isotopes and about 8 g of radioactive isotopes of europium.

The resulting mixture of europium and gadolinium was processed in a facility. The initial solution of europium and gadolinium was transferred to a separation cell.

Sodium amalgam was formed in the electrolysis cell at a current strength of 5 A and a voltage of 12 V. Mercury was fed into the cell with a screw at a rate of 4 ml / min. Under these conditions, the concentration of sodium in the amalgam was 0.11%. (When mercury was supplied at a rate of 2 ml / min, the concentration of sodium in the amalgam was 0.165%).

Amalgam of sodium from the electrolysis cell through a water trap entered the separation cell, in which sodium reduces europium to the metal, leaving gadolinium in ionic form. Metallic europium interacts with mercury to form the europium amalgam, which, through a water trap, enters the 1st regeneration cell. From europium amalgam in the 1st regeneration cell, 99.9% of europium is washed out with a solution of nitric acid into a separate fraction, from which it is released in the form of europium oxide. Mercury from the 1st regeneration cell enters the 2nd and 3rd, completely freeing from impurities. Purified mercury flows by gravity into a container for collecting mercury, from which it is fed by a screw into the electrolysis cell. Thus, the installation works in automatic mode. The solution with gadolinium after the end of the process was drained from the separation cell and gadolinium was recovered in the form of oxide. After the 1st cementation cycle, gadolinium contained 0.55 Ci of europium isotopes. That is, the coefficient of purification of gadolinium from europium was equal to 2 · 10 ³ . The necessary purification of gadolinium was achieved in subsequent cementation cycles.

Claims (1)

A device for separating radioactive elements with different ability to form amalgams, characterized in that it has electrolysis, separation and regeneration cells arranged vertically one below the other, equipped with stirrers located on one shaft, a container for collecting regenerated mercury, a pipe transporting a screw tightly seated in a pipe and rotating with it with a separate drive, mercury moves from cell to cell through hydraulic locks under the action of gravity.