The method of selection of the radionuclide carbon -14 from neutron-irradiated aluminum nitride

 

(57) Abstract:

Usage: in Radiokhimiya upon receipt of the radionuclide carbon - 14. The inventive method consists in a preliminary heat treatment of the target material (AlN) in a stream of oxygen at a temperature of 800-850oC for 5 to 30 hours to remove impurities of carbon-12, the irradiation of aluminium nitride in the neutron flux and, finally, the annealing of the irradiated material in an atmosphere of oxygen at a temperature 920-1180oC for 1 to 5 hours to extract from him radionuclide carbon-14. The method can reduce the duration of heat treatment of irradiated aluminum nitride, as well as an increase in the specific radioactivity of the final product. table 2.

The invention relates to the field of radiochemistry and can be used in the production of the radionuclide carbon-14, which is widely used for the synthesis of labeled compounds.

A method of obtaining carbon-14 from neutron-irradiated aluminum nitride, whereby fine powder of AlN is first heated in a stream of oxygen for 30 min to a temperature of 600-700oC, and then increase the temperature to 900oC and support it to the full oxide is produced by the material, due to the fact that at 900oC the oxidation process of aluminum nitride is quite slow, in addition, this method can not be used when working with piketirovany irradiated aluminum nitride.

Closest to the claimed method is the extraction of carbon-14 from neutron-irradiated aluminum nitride, namely, that of AlN after irradiation in the form of powder or pellets are heated in a stream of oxygen at a temperature 920-1180oC for 5 h /2/. When loading of aluminium nitride in a microwave reactor in powder form is almost complete burnout of the target product. However, when loading AlN in the form of tablets under the same conditions, the degree of extraction of carbon-14 is only 50% it Should be noted that this method does not allow to obtain the carbon-14 good quality, as contained in the original aluminum nitride stable isotope carbon-12 after irradiation and subsequent heat treatment in a stream of oxygen is also provided in the form of carbon dioxide and polluting the target of the drug, reducing its specific radioactivity.

An object of the invention is the increase in the specific radioactivity of carbon-14 to be extracted from the SS="ptx2">

This task is solved in that the original aluminum nitride before irradiation is subjected to heat treatment in a stream of oxygen at a temperature between 800 and 950oC for 5-30 hours Proposed processing mode allows you to virtually eliminate carbon-12 from the original target of the drug. Thus the oxidation of aluminum nitride practically does not occur, i.e., the nitrogen content therein remains unchanged. Subsequent processes reactor processing and oxidative roasting allows to obtain the product of carbon-14 higher specific radioactivity.

Comparison with the prototype shows that this method of obtaining a radionuclide carbon-14 from irradiated aluminum nitride by thermal oxidation in a stream of oxygen differs in that the aluminum nitride before irradiation pre-cleaned the stable carbon-12 at a temperature below the oxidation of AlN. In addition, when using this method achieves a more complete extraction of the target component from irradiated aluminum nitride.

Example 1. 50 g of the powder of aluminum nitride with the original carbon-12 in it to 0.33 wt. irradiated 121 day in the neutron flux 5,951013neutrons/cm2oC for 1 h was achieved almost complete recovery of carbon-14, which is in the form of dioxide is absorbed by a solution of barium hydroxide. The resulting barium carbonate had a specific radioactivity of 0.32 CI/g of carbon (1,181010Bq/g).

Example 2. 50 g of the same powder of aluminum nitride as in example 1 before irradiation was heated in a stream of oxygen for 5 hours at a temperature of 800oC. the content of carbon-12 in it decreased to 0.16 wt. After irradiation and heat treatment on the above modes (example 1), the specific radioactivity of the preparation of carbon-14 was 0.61 CI/g of carbon (2,331010Bq/g), i.e., increased 1.9 times.

Other examples are given in table. 1 (consumption of oxygen in the examples in table experiments was the same and amounted to 40-50 l/h).

Note,

1. When the temperature 90050oC cleanse AlN from carbon-12 is inefficient, since the aluminum nitride begins to be oxidized to aluminum oxide, thus reducing the proportion of the target element nitrogen, which is formed of carbon-14 when irradiated AlN in the neutron flux.

2. In the last column of the table. given the relative is counter-intuitive characteristic of the same drug (Aoextracted from neutron-irradiated AlN, not subjected to pre-treatment (example 1).

During the cleaning of aluminum nitride from carbon-12 less than 5 hours, the specific radioactivity emitted carbon-14 has increased slightly. Increase cleaning time in excess of 30 hours does not give a positive effect.

In addition, in the allocation of carbon-14 from tablets irradiated aluminum nitride proposed method achieved almost complete removal of the target product, while similar to the characteristic shown in the prototype, reaches only 50%

As can be seen from the table. in the time range 5-30 h a significant increase in the specific radioactivity of selected carbon-14 regardless of the form in which the aluminum nitride loaded into an oven (powder or tablets). You get a final product that has 2-3 times higher specific activity than when using as a target AlN, not subjected to a preliminary heat treatment in a stream of oxygen.

In table. 2 shows data on the burning of carbon-14 from both powder and tablets irradiated aluminum nitride contained in the prototype, as well as obtained using PvE pressing and pre-sintering of the pellets in both cases the same.

Are given in table. 2 evidence suggests that, compared with the prototype of the proposed method allows to increase the degree of extraction of the target product.

The method of selection of the radionuclide carbon-14 from neutron-irradiated aluminum nitride, which consists in heating the irradiated aluminum nitride in the form of powder or pellets in a stream of oxygen at 920 1180oC for 1 to 5 hours, wherein the aluminum nitride before irradiation is subjected to heat treatment in a stream of oxygen at 800 850oC for 5 to 30 hours

 

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