Bismuth-213 radionuclide obtaining method

FIELD: power industry.

SUBSTANCE: solution containing radionuclides thorium-229, thorium-228 and daughter decay products of these radionuclides is bubbled with gas, thus extracting from them one of daughter radionuclides of thorium-228 - gaseous radon-220. Gas is supplied through aerosol filter to sorption device, and cleaned solution containing mixture of radionuclides thorium-228, thorium-229, as well as daughter decay products of these radionuclides are supplied to radiochemical processing by means ion-exchange resins in order to obtain target radionuclide bismuth-213. As bubbling gas there used is air and/or helium and/or argon and/or krypton and/or xenon. As sorption device there used is hollow volume the dimensions of which provide the residence time of radon-220, which is sufficient for its complete decay to stable radionuclide lead-208, or trap with activated carbon.

EFFECT: reducing the radiation dose intensity in the work area.

4 cl

 

The invention relates to a technology for production of radionuclides for nuclear medicine, in particular for the treatment of cancer.

In the treatment of cancer becoming more widely used are α-emitting radionuclides. This is due to the large initial energy (5-8 MeV) and short run (tens of microns) of α-particles in biological tissues and, consequently, a high level of Targoviste in the field of localization decaying nuclides. The native α-emitting radionuclides (monoclinally antibodies, peptides with high specificity can deliver them right into the tumor site or metastatic lesion. Due to the small runs of α-particles is possible selective effects of radiation on pathological objects with minimal radiation exposure to surrounding healthy tissues.

The present invention can be used to create generators α-emitters thorium-229/anemone-225 (229Th/225Ac) and anemone-225/bismuth-213 (225Ac/213Bi), finite elements in the decay chain which radionuclides anemone-225 and bismuth-213 can be used as part of medical radiopharmaceuticals, and anemone-225 as "parent" of a radionuclide generator anemone-225/bismuth-213.

PRIOR art

One of the promising directions in nuclear medicine is e is radioimmunotherapy using α-emitters. The use of short-lived α-emitting radionuclides for cancer therapy is of interest from a radiobiological point of view because it is the most effective way of lethal destruction of tumor cells due to the short run of α-particles in tissue and high ionizing ability.

Collectively, nuclear, chemical and biomedical parameters is considered to be the most promising radionuclide213Bi (T1/2=45,6 min). Ongoing clinical trials of this radionuclide show its high efficiency in the treatment of cancer. It is particularly important that the radionuclide213Bi can be used early in the treatment of almost all types of cancer and also as a Supplement to other forms of therapy (surgery, chemotherapy).

Bismuth-213 is the product of the decay chain radionuclides, the initial elements of which are long-lived radionuclides of the uranium-233 (T1/2=159 thousand years) and thorium-229 (T1/2=7340 tel years).

In terms of long-term prospects for the production of α-emitters in nuclear medicine is a crucial life of thorium-229, as a starting material to obtain the target radionuclide bismuth-213. Proposed several ways to obtain t the rija-229 [Isotopes: properties, the receiving application. In 2 volumes. Tom. Edited Vounaria. M, FIZMATLIT, 2005, str-389]:

- from stocks isotope uranium233U;

in a nuclear reactor as a result of multiple captures of neutrons isotope of radium226Ra the reaction226Ra(3n, 2β)229Th;

in a nuclear reactor during irradiation isotope of thorium230Th fast neutrons in the reaction230Th(n, 2n)229Th;

as a result of exposure230Th protons at the cyclotron reactions230Th(p, pn)229Th and230Th(p, 2n)229Pa(1,4 d, β-)229Th.

Unfortunately, the above methods of obtaining thorium-229 have the disadvantage that upon irradiation of natural thorium simultaneously with radionuclide thorium-229 accumulated radionuclide thorium-228. For example, during irradiation in the reactor radium-226 share of thorium-228 in the target reaches huge values - depending on the irradiation conditions from 25 to 50 wt.% [Wounaan, Nsamankow Nuclide programs RRC "Kurchatov Institute": the past, present, and future. // Conversion in mechanical engineering. No. 3, 2000, p.38-47].

Artificial isotope of uranium, uranium-233 produced in the course of irradiation of natural thorium in the nuclear reactor in the radiative capture of neutrons:

232Th(n, γ)→233Th→233Pa→233U.

In parallel with the formation of uranium-233 during irradiation in the reactor nature is underwater thorium occurs formation of radionuclide thorium-228 in the following reactions:

232Th(γ, n)231Th→231Pa(n, γ)232Pa→232U⇒228Th

232Th(n, 2n)231Th→231Pa(n, γ)232Pa→232U⇒228Th

232Th(n, γ)233Th→233Pa(γ, n)232Pa→232U⇒228Th.

The equilibrium concentration of uranium-232 and, accordingly, thorium-228, depending on the conditions of irradiation of thorium in a reactor is in the range 1000-6000 mm. ppm [Wemmerlov, Mofchanov, Angeles "the Use of thorium in nuclear reactors". Energoatomizdat. M., 1983].

Bismuth-213 is a typical radionuclide generator and finds application mainly in the form of labelled them of monoclonal antibodies and other molecular media.

A method of obtaining a radionuclide, bismuth-213 [C.Apostolidis, R.Molinet, G.Rasmussen, and A.Morgenstem Production of Ac-225 from Th-229 for Targeted α Therapy. // Anal. Chem. 2005, 77, 6288-6291]. To obtain bismuth-213 use two generator system229Th/225Ac and225Ac/213Bi. First of thorium-229 is maintained for some time (several tens of days) for the accumulation of daughter products decay (DPR), then anemone-225 along with the rest of the DPR is separated from the thorium-229 due to the anion-exchange separation of the nitric acid solution, then the cation of weak nitric acid solution carry out the separation sea anemone-225 and radionuclides radium. In the second system (225 Ac/213Bi) from Actinia-225 using cation-exchange resins and various acids allocate the target radionuclide bismuth-213.

A prototype of the selected method of producing bismuth-213 radiochemical redistribution solution containing other radionuclides thorium thorium-229, described in [Vmoshninov, Webpublic, ASI and other "Control of technological processes in the development of medical generators225Ac/213Bi and224Ra/212Bi alpha - and gamma-spectrometric methods." // Nuclear energy, No. 3, 2003, str-126].

As a source of raw material for radionuclide bismuth-213, the authors used a mixture of radionuclides of the thorium containing among other radionuclides of the thorium-229 and thorium-228. To obtain bismuth-213 has completed the following transactions:

- well-refined solution radionuclides thorium (thorium-229, thorium-228 and thorium-232) in concentrated (8 molar) nitric acid was kept approximately thirty days to accumulate one of the daughter products of the decay (DPR) - radionuclide anemone-225;

after aging the solution containing the radionuclides of the thorium and DPR was passed through a column of anion exchange resin;

the radionuclides of the thorium from a solution of concentrated nitric acid was barbirollis on the anion exchange resin, and the DWP, including anemone-225, was collected at the outlet of the column;

- received Rast is the PR, containing the DWP, including anemone-225, was diluted with water and brought to odnomestnoi concentration of nitric acid;

- the Department of sea anemone-225 from radium isotopes and other DPR conducted by adsorption sea anemone-225 on the cation exchanger from odnopolyarnogo solution of nitric acid followed by rinsing of the sorbate solution of the same pH;

- desorption sea anemone-225 from the column was performed 3,0-10,0 molar solution of nitric acid or hydrochloric acid;

- obtained solution of sea anemone-225 was kondicionirovanie to odnomestnoi concentration of nitric acid and from barbirolli anemone-225 on the cation exchanger. After soaking sea anemone-225 on the cation exchanger within 1-5 hours to accumulate the desired activity of the bismuth-213 through the cation exchanger missed the solution, extracting bismuth-213 (parameters extraction solution are selected based on the requirements of the consumer bismuth-213, for example lamivudin solution may be 0.01 M solution of DTPA - Diethylenetriamine-N,N,N',N",N"-pentaoxa acid or 0.1 M HI - itestosterone acid);

- at the last stage was conducted air conditioning solution of bismuth-213 to the required parameters.

Nuclear transformations in the decay chain of thorium-228 is accompanied by intense gamma rays with energies up to 2.6 MeV. One milligram of thorium-229 and its decay daughters in equilibrium creates at a distance of 50 cm dose rate of about 1.2 Mr/HR, thorium-228 with whom their DPR under the same conditions creates the dose rate hundreds of times faster. It should be emphasized that the main contribution (up to 85%) in the dose load when working with a mixture of radionuclides thorium-228, thorium-229 generates the final radionuclide chain of thorium-228 - thallium-208.

Because of the high radiation power to ensure the safety of staff radiochemical work allocation sea anemone-225 and bismuth-213 is carried out in protective chambers - "light" with the local biological defense) or "heavy" with remote control processes, which significantly complicates the work. High doses have a negative impact on the used chemicals and ion exchange resins (change or disappear useful properties), equipment containing electronics (equipment fails).

The method of producing bismuth-213 adopted for the prototype, has the following main drawbacks:

- in the original solution of the radionuclide thorium-228 and thorium-229 while the shutter is accumulated impurity daughter products of the decay of thorium-228, which affect all subsequent operations and significantly increase the dose of radiation. This radiation causes increase biological protection to ensure the safety of staff, to take additional measures to prevent or reduce radiolysis of ion-exchange resins, organic extractants and chemical reagents and additional the additional the radiation protection of electronic equipment, used in the work, switch to remote control (with the use of mechanical manipulators) technological operations.

DISCLOSURE of INVENTIONS

Object of the invention is the improvement of the technological process of obtaining a radionuclide bismuth-213 to reduce the dose of radiation during technological processes.

To solve the problem in the method of producing a radionuclide bismuth-213, including radiochemical redistribution solution containing a mixture of radionuclides thorium-228, thorium-229, and daughter products of the decay of these radionuclides, and sequential extraction of this solution with ion exchange resins radionuclide bismuth-213, are invited to pre-solution containing radionuclides of the thorium-229, thorium-228 and daughter decay products of thorium-229 and thorium-228, barbthroat gas and to remove from the solution of one of the daughter radionuclide thorium-228 - gaseous radon-220, and send it via aerosol the filter on the sorption device, and the purified solution containing a mixture of radionuclides thorium-228, thorium-229 and daughter decay products of these radionuclides, send radiochemical redistribution using ion exchange resins to obtain targeted radionuclide bismuth-213.

The bubbling fluidised bed gas using air and/or the men, and/or argon and/or krypton and/or xenon.

As a sorption device using hollow volume, the size of which provide the residence time of radon-220, sufficient for its full decay to stable lead-208.

As sorption devices use the trap with activated charcoal.

This "parasitic" activity, create a workplace additional dose will accumulate in the sorption device. The sorption device may be removed or at a safe distance or isolated biological protection while radon-220 does not decay to the stable isotope lead-208. The sorption device (it can be a long tube, or a large vessel or trap with a sorbent, such as activated charcoal) should ensure that the time of flow through the gas flow is not less than 10 minutes (about ten half-lives of radon-220 - 55,6).

In the proposed method of obtaining a radionuclide bismuth-213 is used among the daughter products of the decay of thorium-228 gaseous radionuclide radon-220, which may be removed from a solution containing a mixture of radionuclides thorium-228, thorium-229, and daughter products of the decay of these radionuclides, and focuses on the sorption device, and the purified solution containing a mixture of radionuclides that is s-228, thorium-229 and daughter products of the decay of these radionuclides, sent for radiochemical redistribution by means of ion exchange resins to obtain targeted radionuclide bismuth-213.

The half-life of radon-220 is of 55.6 seconds, allowing its removal from aqueous acid solutions by using a sparging gas [Schema decay of radionuclides. The energy and intensity of radiation. Publication ICRP 38. In two parts. Part two. Book 2. M, Energoatomizdat, 1987, str-205].

The inert gas radon 6.7 times heavier than air, has a low solubility in water [Assenov, Utebayev Isotopes of radon and their degradation products in nature. M, Atomizdat, 1975]. Due to the low solubility of radon escapes easily from the water into the air. In thermal waters with temperatures above 30°C, the solubility of radon in water is reduced by half with respect to the so-called "cold" radon waters with temperatures up to 10°C. Rapid radon in the air also contributes to the saturation of radon waters by nitrogen and carbon dioxide. According to some authors, the loss of radon from water released from her carbon dioxide reaches 36%.

Isotopes of radon in extremely rare cases, enter into chemical compounds. Chemical compounds of radon-220 is not known.

In the presence in solution of splawa the observed gas bubbles atoms of radon in the process of diffusion in the liquid penetrate into the volume of the bubbles and are carried to the surface of the solution. Next, the flow of the gas radon-220 is transported by technological gas communications and its transfer to the recovery system, where holding up to the complete collapse in the stable element lead-208.

The proposed method for radionuclide bismuth-213 has advantages in comparison with the described prototype:

all technological operations, starting with the first (extract solution of a mixture of thorium-229 and thorium-228 for accumulation target DPR) due to the removal from solution of gaseous radioactive radon-220 and its decay daughters (including thallium-208) significantly reduced the dose of ionizing radiation;

- significant reduction in dose rate ionizing radiation in the technological process allows to reduce the capacity of biological protection while maintaining safety standards for personnel and for equipment and chemical reagents;

- reduction of the capacity of biological protection may allow you to navigate with the remote control processes (which really limits the ability to "manual" and significantly reduce the cost of the work (the cost of protective equipment is the main part of the cost, the cost of protective equipment depends substantially on its "power" - dose ionizing radiation, in which the protective equipment is provided to staff prior to stymie by the standards of the dose).

An EXAMPLE of carrying out the INVENTION

As a source of raw material for radionuclide bismuth-212, a mixture of radionuclides thorium (thorium-229, thorium-228 and thorium-232).

To obtain bismuth-213 mixture of radionuclides of the thorium and the resulting daughter products of the decay of these radionuclides is kept in a solution of nitric acid (8MHNO3placed in the flask-bubbler volume of 50 ml Total volume of solution of 10 ml.

The tube immersed in an acid solution in the flask-bubbler using a peristaltic pump, air is injected with a flow rate of ~50 ml/min as the pumped gas can be used any of the mentioned in the formula gases or their mixtures. The air was selected as the most affordable gas.

After passing the solution the air containing the atoms of radon-220, via aerosol filter comes sorption volume, which is a PTFE tube with a diameter of 8 mm and a length of over one meter or gas trap with activated carbon. Sorption volume surrounded by the lead biological protection. The time course of gas sorption amount sufficient for complete decay of radon-220 and subsidence of its daughter nuclides ("solid" radionuclide lead-212) on the tube wall. Cleared from the DWP air in the closed circuit is returned to the flask bubbler with the initial solution of radionuclides Tory is -229 and thorium-228.

The duration of the sparging of the solution containing the radionuclide thorium-228, thorium-229, subsidiaries and their degradation products, is not less than 50 hours and provides a complete collapse in the initial solution accumulated radionuclide lead-212 - parent radionuclide thallium-208, giving the largest contribution to the dose rate of gamma radiation solution of thorium-229 and thorium-228. After 50 hours the solution, purified from the daughter products of the decay of thorium-228, sent for radiochemical redistribution using ion-exchange resins for targeted radionuclide bismuth-213, according to the technology described in method chosen for the prototype [Vmoshninov, Webpublic, ASI and other "Control of technological processes in the development of medical generators225Ac/213Bi and224Ra/212Bi alpha - and gamma-spectrometric methods." // Nuclear energy, No. 3, 2003, str-126].

All solutions, including the solution in the flask-bubbler, are subjected to spectrometric analysis to determine the radionuclide composition and information material balance.

The proposed method of producing bismuth-213 allows, in comparison with the method chosen for the prototype, significantly reduce the dose of radiation at the place of work that will lead to a decrease in the power required shielding to perform safety standards as the La staff, so for the equipment and chemical reagents. The decrease in the power of biological protection may allow you to navigate with the remote control processes (which really limits the ability to "manual" and significantly reduce the cost of the work (the cost of protective equipment is the main part of the cost, the cost of protective equipment depends on its "power").

1. A method of producing a radionuclide bismuth-213, including radiochemical redistribution solution containing a mixture of radionuclides thorium-228, thorium-229 and daughter products of the decay of these radionuclides, and sequential extraction of this solution with ion exchange resins radionuclide bismuth-213, characterized in that the solution containing the radionuclide thorium-229, thorium-228 and daughter decay products of thorium-229 and thorium-228, bubbled gas, thereby removing one of the daughter radionuclide thorium-228 - gaseous radon-220, and direct the gas through particulate filter on the sorption device and the purified solution containing a mixture of radionuclides thorium-228, thorium-229, and daughter products of the decay of these radionuclides are sent to radiochemical redistribution using ion exchange resins to obtain targeted radionuclide bismuth-213.

2. The method according to claim 1, characterized in that as a bubbling fluidised bed gas use air or helium, and/or argon and/or krypton and/or xenon.

3. The method according to claim 1, characterized in that as a sorption device using hollow volume, the size of which provide the residence time of radon-220, sufficient for its full decay to stable lead-208.

4. The method according to claim 1, characterized in that as sorption devices use the trap with activated carbon.



 

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SUBSTANCE: solution containing mixture of radionuclides thorium-228 and thorium-229, as well as daughter decay products of these radionuclides is bubbled with gas, thus extracting from them one of daughter decay products of thorium-228 - gaseous radionuclide radon-220. Gas is supplied through aerosol filter to sorption device where as a result of radioactive decay as per chain 220Rn→216Po→212Pb there accumulated is radionuclide lead-212, which, after attainment of saturation of activity of lead-212, is desorbed. The obtained solution is supplied to column with ion-exchange resin from which the daughter decay product of radionuclide bismuth-212 is washed from time to time. As bubbling gas there used is air and/or nitrogen and/or helium and/or argon and/or krypton and/or xenon. As sorption device there used is hollow volume the dimensions of which provide the residence time of radon-220, which is sufficient for its complete decay to radionuclide lead-212, or trap with activated carbon.

EFFECT: reducing the labour intensity of the process and the content of doping radionuclides.

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