Method of obtaining thorium-228 radionuclide

FIELD: physics.

SUBSTANCE: in the disclosed method of obtaining a 228Th radionuclide, which involves irradiating a target, the target material is a natural thorium isotope - 230Th, the target is placed in a linear electron accelerator and irradiated with γ-quanta of deceleration radiation, and the desired 228Th radionuclide accumulates therein during the threshold nuclear reaction 230Th(γ,2n)228Th. The target material can be 230ThF4 or 230ThO2 or 230Th metal.

EFFECT: obtaining α-radiating nuclides, which enables to eliminate shortage of therapeutic α-radiators on the market of medical radionuclides and satisfy increasing demand in the future.

2 cl

 

The technical field

The invention relates to a reactor technology for production of radionuclides for nuclear medicine.

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 a high level of energy 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-228/lead-212 (228Th/212Pb) and lead-212/bismuth-212 (212Pb/212Bi), the final element of the chain of decays which the radionuclide212Bi is used directly in the composition of the drug. Thus, of key importance is the production of the initial element of the chain - of radionuclide228Th.

Prior art

One of the most promising directions in nuclear medicine is t the targeted 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.

Currently an intensive search for α-emitters with acceptable nuclear-physical properties. Radionuclide212Bi formed by

the decay of228Th, is considered one of the most promising for use in cancer treatment.

The half-life of212Bi≈60,6 min, the average energy of the α particles of 7.8 MeV. In the decay of212Bi are formed radionuclides208Tl and212Ro, which lead to stable nuclide lead208Pb. Linear energy transfer (let) is ~80 Kev/μm, and the mileage of α-particles in biological tissue is less than 100 μm, which corresponds to only a few cell diameters.

Bismuth-212 is a typical radionuclide generator and finds use in radioimmunotherapy, mainly in the form of labelled them of monoclonal antibodies and other molecular carriers. The initial element of the chain collapse, leading to212Bi is the radionuclide228Th period of polur the decline of T 1/21,913 year. [Wahlbin and others, "Radionuclides for radiotherapy" // radiochemistry, 1997, t, No. 6, str-490]. To obtain212Bi may use two generator systems228Th/224Ra and224Ra/212Bi. The first224Ra is separated from the228Th through anion-exchange separation of these radionuclides from solution of nitric acid. The second generator of the224Ra secrete212Bi using cation-exchange resins and mineral acids [V.M. Savinov, V.B. have been Pavlovich, A.A. Kotovsky and other "Control of technological processes in the development of medical generators Ac-225-Bi-213 and Ra-224-Bi-212 alpha - and gamma-spectrometric methods" //Nuclear energy, No. 3,2003, str-126].

Because212Bi is a daughter product of the decay of the radionuclide228Th, in the manufacture of medical radionuclide212Bi determines the importance of the process of obtaining228Th, as the source material.

A method of obtaining a radionuclide,228Th [V.M. Savinov, V.B. have been Pavlovich, A.A. Kotovsky and other "Control of technological processes in the development of medical generators Ac-225-Bi-213 and Ra-224-Bi-212 alpha-and gamma-spectrometric methods." Izvestiya vuzov. Of nuclear energy. No. 3, str, 2003], which consists in radiochemical selection228Th of the "old" stocks233U, p is outstay admixture 232U, a daughter product of the decay of which is228Th. However, to rely on the wide involvement of the233U (and, correspondingly,232U) in the production process228Th is not necessary due to the difficulty of obtaining this isotope of uranium.

As a prototype the selected method of obtaining228Th, consisting in the accumulation of228Th in the target of radium-226 (226Ra), irradiated with neutrons in the high flux reactor [VY sheep, NS Marchenkov, Nuclide program RRC "Kurchatov Institute": the past, present, and future. Conversion of mechanical engineering, 2000, No. 3, p.38-47]. In the double neutron capture in the target accumulates228Th.

Significant disadvantages of the prototype are high radiotoxicity of the target material, the uniqueness of the high flux reactor, the operation of which is based the method of obtaining228Th of226Ra, and the process is multi-stage and is carried out by successive capture of two neutrons, as a result, the yield of the final product is low and cannot meet the growing market demand therapeutic α-emitters.

Disclosure of inventions

The basis of the invention is the creation of technology-based method of obtaining α-emitting nuclides, based on the use of available cheap raw materials, posvalue is about to eliminate the deficit therapeutic α-emitters in the market of medical radionuclides and to meet the growing needs in the future.

The problem is solved by the fact that in the method of producing a radionuclide228Th, including the irradiation of the target, as the target material take natural isotope of thorium -230Th, the target is placed in a linear electron accelerator and irradiated with γ-rays bremsstrahlung, and in the process threshold nuclear reactions230Th(γ,2n)228Th accumulate it targeted radionuclide228Th.

As the target material can be used connection230ThF4or230ThO2or metal230Th.

In the proposed method of production228Th used the existence of natural radionuclide230Th - product of the natural decay of238U. it is Known that radioactive decay of238U in the chain of child products in addition to isotope234U, are formed long-lived α-emitters: isotope230Th, and isotope226Ra with half-lives respectively 8,1·104and 1.59·103years. The content of these isotopes in natural uranium is estimated by the following figures: thorium 17.9 g/t of uranium and radium 352 mg/t of uranium. In the processing of uranium ores and radioactive isotopes emit as by-products [Webscience, Benadryl, the Technology of uranium, gosatomizdat, Moscow, 1961].

The enriched uranium hexafluoride UF6thorium is separated and remains in the "stubs" when CFT is rirovanie [Matveev L.V. etc.. the Problem of accumulation of232U and236Pu in a nuclear reactor, "Nuclear technology abroad", 1980, No. 4, p.10-17]. However, the main source of230Th, available for use at present, are a waste dump in the separation of UF6 production, where during long-term storage is its accumulation [Smirnov, Y. and others, Handling, removal and disposal of mining waste production, "Nuclear technology abroad", 1981, No. 3, p.15-20].

The irradiation of targets containing230Th, in the electronic accelerator, the reaction230Th(γ,2n)228Th in the target store target radionuclide228Th.

Accumulated in the target228Th has a genetic decay chain elements, leading to radionuclide212Bi, which is directly used in radioimmunotherapy [VA Halkin and other Radionuclides for radiotherapy. Radiochemistry, 1997, t, No. 6, str].

The proposed method of obtaining228Th has significant advantages compared with prototype:

- targeted radionuclide228Th receive, using as starting material a by-product in the processing of uranium ore -230Th

- reduces the radiotoxicity of the target material;

- to retrieve the target radionuclide228Th use fairly common and relatively simple will accelerate the l electrons with energies of ≈50 MeV.

An example of carrying out the invention

The target containing the radionuclide230Th in the form of a metallic thorium mass 10 g is placed in the electronic accelerator with electron energy of 50 MeV. Thorium is sealed in the body of the target, made of refractory metal is tantalum. In the irradiation process, a duration of 240 hours, the resulting threshold nuclear reactions230Th(γ,2n)228Th in the target store target radionuclide228Th, which is the primary element in the decay chain radionuclides leading212Bi directly used in radioimmunotherapy.

After irradiation, the target containing228Th, is extracted from the accelerator, is kept in a month to reduce the induced activity of the material of construction of the hull of the target, then it produce thorium, dissolving it with hydrochloric acid, and is used for radionuclide212Bi.

The proposed method of obtaining228Th allows, in comparison with the method chosen for the prototype, to reduce the complexity of the process, to reduce the radiotoxicity of the target material by using as starting material a by-product uranium production230Th.

1. A method of producing a radionuclide thorium-228, including the irradiation of the target, characterized in that as the target material take natural from the top of thorium - 230Th, the target is placed in the electronic accelerator, is irradiated with γ-quanta-ray accelerator, where in the process a threshold nuclear reactions230Th(γ,2n)228Th accumulate in target target radionuclide thorium-228.

2. The method according to claim 1, characterized in that as the target material use connections230ThF4or230ThO2or metal230Th.



 

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