A method of producing a radionuclide carbon-14 and device for its implementation

 

(57) Abstract:

The invention relates to applied radiochemistry and relates, in particular, production to obtain a radioactive isotope of carbon14With widely used as labeled organic compounds, as well as in the sources of radiation. The inventive purified from impurities calcium nitrate before irradiation is melted at a temperature of 500 - 510oC in the atmosphere of nitrogen oxides at a pressure of 0.2 - 0.5 MPa. Pieces of melted substance is loaded into the container, leaving a portion of the free volume. After irradiation in a neutron flux pierce the lid of the container and the portions served through holes formed nitric acid for the dissolution of irradiated substances, while stirring container up to 150 - 200oC. From the container periodically blown gaseous compounds of carbon-14 and sent for recycling. A device for implementing the inventive method consists of a metal container and cover having at the opposite ends of the recess. Inside the container along the entire height of the laid pipe for supplying nitric acid, which is tightly connected with one of the recesses of the cover. The second recess is intended for removal from contee deepening pierced another hole. An advantage of the claimed invention is to increase the output of carbon-14 high isotopic purity, reducing the number of generated radioactive waste, and improving the technological process. 2 S. p. f-crystals, 1 tab., 1 Il.

The invention relates to the field of applied radiochemistry and relates, in particular, production to obtain a radioactive isotope of carbon14With widely used as labeled organic compounds, as well as in the sources of radiation.

Education radionuclide carbon-14 is carried out by nuclear reactions14N(n, p)14With the irradiation of targets in a nuclear reactor by neutron flux. For the preparation of targets using different nitrogen compounds. A method of obtaining carbon-14 from irradiated in a nuclear reactor chetyrehokisi nitrogen /1/ Packed in containers. The disadvantage of this method is the low yield of the final product, due to the low density of the starting material. This method is implemented using a device consisting of aluminum container for liquid nitrogen-containing substances containing two tubes to fill the target and the gas phase selection connected with capacity stainless what is the necessity of using long inlet and outlet pipes, located in the reactor core, which leads to their high induced activity, and placement of recycling systems in the reactor hall, which complicates the possibility of the method. There is also known a method of producing carbon-14 from neutron-irradiated aluminum nitride /2,3/, according to which the aluminum nitride after irradiation in the form of powder or pellets are heated in a stream of oxygen at a temperature of 920 -1180oC for 1 -5 h, and the aluminum nitride before irradiation is subjected to heat treatment in a stream of oxygen at a temperature of 800 - 850oC for 5 to 30 hours the Disadvantages of this method are the need to work with highly radioactive substances at high temperatures and the formation of large quantities of high level waste.

The closest analogue method is a method of obtaining carbon-14 by irradiating the container with dry powdered calcium nitrate in a nuclear reactor, followed by dissolving the shells of the containers in the alkali solution, and then the decomposition of calcium carbonate with a solution of nitric acid /4/.

The closest similar devices in the same /4/. The device consists of a metal container for starting vedeti carbon-14 and the resulting radioactive waste.

Disadvantages of the method according closest analogue is the low volumetric content of nitrogen in the irradiated target (bulk density dry salt is about 1 g/cm3therefore, the volumetric content of nitrogen is only 0.17 g/cm3), the formation of large quantities of liquid radioactive waste by dissolving the shells of the containers and irradiated salt.

The disadvantage of the nearest similar devices is the necessity of immersing the container with irradiated material in the reagent solution is that, when dissolved leads to getting into the final product of stable compounds of carbon contained in the contamination of the external surface of the container and the material.

Task to be solved by the claimed method, is to increase the output of carbon-14 high isotopic purity, reducing the number of generated radioactive waste and improving the maintainability of the way.

Task to be solved by the claimed device is increased use of the functionality of the container for irradiation of the starting materials.

The essence of the method is that refined calcium nitrate before irradiation is melted at a temperature of 500 - 510 is esta, leaving part of the free volume after irradiation in a neutron flux removing radionuclide carbon-14 is carried out in the container by piercing the cover and feeding it through the holes formed in the portions of nitric acid, while stirring it to a temperature of 150 - 200oC and periodically blowing the resulting products in the system processing flow of gas not containing carbon compounds.

In the proposed method, instead of dry powdered calcium nitrate in containers placed fused, which has a higher density of 2.36 g/cm3) and volumetric content of nitrogen (0.39 g/cm3). This allows for the filling of the container pieces fused salt to get the win for the life of carbon-14 is more than 1.5 times. The presence of free volume formed between the pieces salt, to allow operation of the reagents directly into the cavity of the container. Thus, the container is irradiated with salt becomes a container, inside which there is the whole process of processing of the irradiated material and excretion of carbon-14. For additional purification from carbon-14 calcium nitrate pre-melted at a temperature of 500 - 510oC in the atmosphere ACS is nom flow targets to obtain products with high specific radioactivity. Exception transactions dissolution of the shell of the container in the proposed method also allows to increase the specific activity of the resulting products.

To extend the functionality of the device when implementing the method proposed container with irradiated salt to use as a container for the entire process of processing of the irradiated material and excretion of carbon-14. For this purpose, the opposite ends of the container cover asked to perform two grooves, intended for installation precollege device delivery system of nitric acid and removal from the container of gaseous compounds of carbon-14, and the inside of the container to establish a supply pipe nitric acid, which is tightly connected with one of the recesses of the cover. The presence of the recesses allows you to remotely interfaced prikolnoe device with the container and to carry out puncture the lid of the container with less effort. The supply pipe of nitric acid in the lower part of the container allows the complete dissolution of calcium nitrate and decomposition generated by the irradiation of nitrite and calcium carbonate, as well as to accelerate the degassing of the resulting solution by ozonation through Regionalliga carbon-14 is used by the device, consisting of a metal cylindrical shell plate 1 (the drawing), the cover 2 is made on its opposite ends with recesses of 3.4. Calcium nitrate in the form of separate pieces 6 fused substance is placed inside the container in a free package to eliminate the negative effects of radiation-induced swelling. Inside the container along the entire height padded tube 5, which after a puncture through the cavities 3 is fed to the nitric acid solution, and then gas for stirring the resulting solution of calcium nitrate and the ousting of dissolved carbon dioxide-14. The tube 5 is hermetically attached to the lid 2 of the container and separated from the outer surface of the septum, which is opened when the puncture. For removal of the upper part of the container gases formed in the lid 2 of the container at the location of the recesses 4 is pierced another hole. The puncture is carried out using precollege device, worn on the cover of the container. Gases from the container is supplied into the system of collection and recycling.

The method and the device are illustrated by the examples, where the sample N 1 illustrates the obtaining of carbon-14 from irradiated in a nuclear reactor chetyrehokisi nitrogen /1/, example N 2 corresponds to the method of example No. 1. In an aluminum container with a volume of 14 liters, fitted with two tubes to fill the target and selection of the gas phase, put 1500 g camerahouse nitrogen and lowered container with a target channel of a nuclear reactor at 220 h, selecting the gas phase in the stainless steel tank every 24 h exposure. From this tank the gas phase was passed through a solution of sodium hydroxide. After irradiation container with the target removed from the reactor, measured by the number of remaining target material, and a solution of sodium hydroxide were combined and precipitated carbon-14 in the form of barium carbonate. The amount of carbon-14 obtained in this way was 2.4107Bq/h or 1,7103Bq/(cm3h). Example No. 2. Aluminum containers with a diameter of 36 mm and a length of 102 mm (volume of 100 cm3) fills dehydrated powdered calcium nitrate (107 g). In the irradiation process was formed to 6.8 MCI carbon-14 per 1 g of nitrogen, i.e., only 120 MCI of C-14 on the container. After irradiation for 3 of the container is loaded into the apparatus, the solvent, it was poured 3.7 M the alkaline solution was heated to 75oC and kept for 1 h to destroy aluminum shell containers. Then the apparatus was filled with concentrated nitric acid and gases blew off Poti or 4,2103Bq/(cm3h), losses could occur due to the leakage through the alkaline trap carbon dioxide, methane and other volatile carbon compounds. In this redesign process was formed 7 litres of liquid radioactive waste.

Example No. 3. In an aluminum container with a volume of 1 l was downloaded 1.6 kg calcium nitrate, pre-melted under pressure and split into pieces. After sealing by welding the container was placed in the irradiation channel of a nuclear reactor. After the end of the campaign, the container was removed from the reactor, the lid with special precollege devices have been made 2 holes, through which was blowing through the internal cavity of the container by the flow of pure nitrogen. Then into the container through an opening in communication with the tube, gradually introduced 300 cm35 M nitric acid. At the bottom of the container was heated on a hotplate to a temperature of 150 - 200oC, necessary for the complete dissolution of calcium nitrate and decomposition formed by irradiation of nitrite and calcium carbonate. The resulting gases are passed through an absorber of nitrogen oxides, the node afterburners and alkaline traps. After entering the acid on the same line within 1 h poetry). The number obtained in this way carbon-14 was 1.2107Bq/h or 1,2104Bq/(cm3h). After completion of the selection process carbon dioxide-14 heating of the container is stopped, while inside it solution hardened, forming a solid crystalline with a small amount of free nitric acid. To improve its stability and removal of the acid in the container through remaining after puncture of his cover holes peppered the solid absorber water and acid - calcium oxide, and then the container was tightly kuprili plugs and transferred for disposal as solid radioactive waste.

Comparative characteristics of the outputs of carbon-14 in various ways to get presented in the table.

The claimed invention (method and device) allow to increase the output of carbon-14 high isotopic purity, to reduce the number of generated radioactive waste and improve the manufacturability of the process.

Bibliography:

1. Russian Federation patent RU N 2106032 MKI.6 G 21 G 01/06, 1/08 "Method of production of the isotope carbon-14"

2. Hata, K., Shikata E., Amano H. Release of Carbon-14 from Neutron-Irradiated Aluminium Nitride in the Dry Procedure.- Journal of Nuclear Science and Technology, 1973, v.l0, N 2, p is irradiated with neutrons aluminum nitride".

4. E. E. Kulish, "Some issues of radioactive isotopes in a nuclear reactor". Obtaining isotopes. Powerful gamma-ray installation. Radiometry and dosimetry. M.: Izd-vo an SSSR, 1958, S. 23-25. The closest analogue.

1. A method of producing a radionuclide carbon-14 by the irradiation of dehydrated calcium nitrate in a metal container with neutrons, the subsequent opening of the container, the dissolution of irradiated substances in nitric acid and feeding the extracted radioactive gaseous product containing carbon-14, in the processing system, wherein the calcium nitrate before irradiation is melted at a temperature of 500 to 510°C. in the atmosphere of nitrogen oxides at a pressure of 0.2 - 0.5 MPa and loaded into a container in the form of pieces of processed substances, and removing the carbon-14 is carried out in the container, piercing the cover and feeding it through the holes formed in the portions of nitric acid, while stirring it up to 150 - 200°C and periodically blowing the resulting products in the system processing flow of gas not containing carbon compounds.

2. A device for receiving radionuclide carbon-14, consisting of a metal container with a lid to download irradiated wasastjerna to install precollege device delivery system of nitric acid and removal from the container of gaseous products, containing carbon-14, and inside the container is installed pipe nitric acid, which is tightly connected with one of the recesses of the cover.

 

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