The method of producing the radioisotope strontium-89

 

(57) Abstract:

Use: for the production of the radioisotope strontium-89, used in medicine in the treatment of cancer. The inventive method involves irradiation with neutrons in a nuclear reactor target containing fissile material, and subsequent removal from the target the target of the radioisotope. The target is performed with the thickness of the dividing layer, providing the ability to exit from the surface of the fragments pressure due to the energy of recoil. The fission fragments are removed from the zone output stream of inert gas, which is served in the filtration area for separating aerosol particles. Then direct the flow into the volume of the pre-exposure, in which the fragmentation of gaseous Kg-89, which is the predecessor of the Sr-89 in the decay chain fission elements with mass 89, separate from other radioisotopes due to their more rapid natural decay. After separation Kg-89 is sent to the recovery system, which can withstand Kr up to the complete collapse in the target radioisotope Sr-89. The technical result is to increase the productivity of the process and use the most common radioisotope research aderinoye receiving radioisotopes.

The present invention can be used for the production of the radioisotope strontium-89, widely used in nuclear medicine for cancer treatment. The Ministry of health in 1999 allowed the application in clinical conditions of the drug "Solution of strontium-89 chloride, isotonic" [the Ministry of health 128 from 15.04.99; registration certificate 99/128/1 from 19.04.99].

Due to the large variety of radioisotopes with their help you can examine and treat any system of the human body: circulatory, respiratory, cardiovascular, digestive, water-salt metabolism, brain and spinal cord. Using radioisotopes can be detected volumetric processes tumors and metastases, inflammatory foci [N. The [. Radiation pharmacology - the revolution in health care. Nuclear society, 2-3, September 1999, pages 35-38] . The production of medical radioisotopes has developed into an important industry, accounting for more than 50 % of the annual production of radioisotopes in the world. On the extent of use of radioisotopes in medicine, says, for example, the fact that today every fourth patient, circulating in the United States in the clinic, and every third coming into the hospital, the direction is of such procedures in the tens of millions.

The rapid development of radioisotope diagnosis and therapy in medical practice due to its ongoing development of new modifications of recording equipment and especially of new radiopharmaceuticals. One of the most modern and effective therapeutic radioisotope is strontium-89. It is used in Oncology for the treatment of pain, allowing you to refuse drugs. Preparation of strontium-89 is introduced into the body, sorbed and distributed by bone metastases, providing long-term analgesic effect, eliminating the need for frequent injecting drug was relieving the patient from habituation effect.

Strontium-89 has the following radiation characteristics:

the half - life of T1/2=50,5 day;

- method decomposition --(decays to a stable isotope89Y);

- maximum energy-particles E=1463 Kev;

the energy associated radiation E=909,1 Kev;

output - quanta - 9,3010-5(BCS)-1.

Known reactor a method of producing the radioisotope strontium-89, consisting of neutron irradiation of natural strontium [C. I. Levin. Getting radioactive is the eye of a nuclear reactor with a thermal spectrum neutrons. Natural strontium has the following isotopic composition:84Sr 0,56%,86Sr 9,9%,87Sr 7,0%, 88Sr is 82.6%. The result for the radiative capture reaction88Sr(n)89Sr in target formed target radioisotope strontium-89. The method is convenient because it is implemented in conventional nuclear research reactor. However, the cross section for the radiative capture reaction in thermal energy of the neutrons is only 610-27cm2that limits the performance of this method. Typically used for irradiation of highly enriched target with content88Sr>99.9% uptime. The use of enriched strontium is connected with the necessity of suppressing the formation of strontium-85 in the reaction84Sr(n)85Sr, which is an undesirable impurity, and the desire to increase the time between target radioisotope strontium-89.

For the selected prototype reactor a method of producing strontium-89, including the irradiation of the target with fissile material in a nuclear reactor and subsequent removal from the target the target of the radioisotope [patent RU 2155398 C1, IPC G 21 G 1/08, publ. 27.08.2000,]. Target is molten-salt nuclear fuel, representing a molten fluoride salts containing fissile material. Under the action of irradiated is strontium-89 in the decay chain of fission fragments with atomic mass 89. Salt melt krypton removed by bubbling an inert gas. In the system recovery krypton-89 stand up to the complete collapse in the target radioisotope.

The disadvantages of this method include the high temperature of the melt and its corrosiveness, which require installation of corrosion-resistant materials, capable of working in a hostile environment. The selection of the radioisotope must be of the recirculating fuel at high vapor pressure of fissile material in the free volume of the fuel channel.

The basis of the invention is based on the requirements of the performance and manufacturability of a new method of producing the radioisotope strontium-89 while maintaining a high specific activity and radionuclide purity, the possibility of use for its production reactors with a thermal spectrum of neutrons.

The problem is solved by the fact that in the method of producing radioisotope Sr-89, including the irradiation of targets containing fissile material by neutron nuclear reactor and subsequent removal from the target the target of the radioisotope, the target is performed with the thickness of the dividing layer, providing the ability to exit from the surface of the stream fed to the filter area, separate aerosol particles, direct the flow into the volume of the pre-exposure, where fragmentation of gaseous Kg-89, which is the predecessor of the Sr-89 in the decay chain fission elements with atomic mass 89, separate from other radioisotopes due to their more rapid natural decay, then send Kg-89 in the recovery system, which can withstand Kg to a complete collapse in the target radioisotope Sr-89.

As fissile material can be used uranium-233, and/or uranium-235, and/or uranium-238, and/or plutonium-238, and/or other transuranium elements.

The irradiation of a layer of fissile material is in an active area of research or power reactor with a thermal spectrum of neutrons.

The basis of the proposed method of production of the radioisotope strontium-89 is based on two parameters that characterize the process of fission of heavy nuclei by neutrons: high recoil energy of the fragment and the presence of genetic decay chain of elements with atomic mass A=8989Se-->89Br-->89Kr-->89Rb-->89Sr gaseous precursor strontium-89 is a radioactive inert gas krypton-89. It is known that formed in the fission of heavy the information is mostly the way the fission fragment loses its energy mainly due to the ionization of atoms of the lattice of fuel. The average mileage of the fragment depends on the properties of inhibitory substances. For the most common type of nuclear fuel uranium dioxide UO2mileage is 6 and 9 μm for heavy and light fragments, respectively [Yu, Degalan, N. N. Ponomarev-Stepnoi, C. F. Kuznetsov. The high-temperature behavior of nuclear fuel during irradiation. M.: Energoatomizdat, 1987, page 103]. There are other estimates of the magnitude of mileage fragments Kg Ha - 10-20 μm [Y. C. Chechetkin, E. K. aksin, C. M. Serkin. Cleanup of radioactive gaseous waste from NPPs. M.: Energoatomizdat, 1986, page 31].

The initial element in the decay chain of fragments with atomic mass A=89 is selenium-89 with a half-life of 0.4 [C. M. Kolobashkin, P. M. Rubtsov, V. D. Ruzhany and other Radiation characteristics of irradiated nuclear fuel. The Handbook. M.: Energoatomizdat, 1983, page 29]. If a division has occurred in the fuel blocks at a depth of not more than the length of the run of the fission fragment in this material or in a thin layer of fissile layer, whose thickness is comparable with the mean free path, due to the high energy impact of the great sources of fragments 89Se will leave fissile material and go into the gas gap separating the fuel and the outer structural shell fuel Eugenie in nuclear physics. M: Atomizdat, 1965, page 389]. Because the half-life of89Se is only 0.4 sec, the time is 2-3 with almost all kernel selenium-89 go to the next element of the chain - bromo-89. In turn,89VG with T1/2=4,6 with disintegrate in a relatively long-lived krypton-89, the half-life of which more than 190 C. the Majority related to krypton-89 fission fragments, which are metals, metalloids or alkaline earth elements tend to be precipitated on the surface of the structure of the fuel channel. The only exceptions are the fragments of krypton and xenon, which during the whole time of its existence remain in the gaseous state, accumulating in the gap between the fuel and the wall of the channel. A stream of inert gas, for example helium or argon, gaseous fragments removed from the gap of the fuel channel and sent to system recovery and purification, where they are separated from aerosols and solid particles, and then send in the amount of pre-exposure, in which the krypton-89, which is the predecessor of strontium-89 is separated from accompanying him radioisotopes due to their natural decay, then a krypton-89 sent to a recovery system where it can stand up to full RA is the process.

Great performance of the proposed method of producing the radioisotope strontium-89 due to the high cross section of the fission (n,f) on these nuclei, as235U233U or239Pu, reaching values 600-80010-24cm2for thermal neutrons, and a significant release of splinter krypton-89 in the act of division is about 4-5%. Estimated performance of the new method will be more than 1000 times higher than in the method, selected as a prototype. A significant difference in half-lives of isotopes of krypton89Kg and90Kr, components respectively 190,7 and 32,2, allows for the exposure of the gas phase removed from the fuel channel, to reduce the impurity content of strontium-90 in the target product to the level of ~ 10-4at.% and thus provide high radionuclide purity strontium-89.

Thin-film layers of nuclear fuel from metal, oxide or other chemical compounds have a number of advantages compared with other fuels, such as molten fluoride or chloride salts, an aqueous solution of salts of uranium. The main of them are:

- ease of production of a uniform film thickness of 5-10 μm from U, UO2or UN along the entire length of the fuel Kahn is on channel;

- compatible with a wide range of structural materials.

The proposed method of production of the radioisotope strontium-89 can be carried out as follows.

The uranium dioxide UO2or uranium metal is applied in a thin layer on the outer surface of cylindrical pipes made of corrosion-resistant metal, which is a part of the fuel channel. The thickness of the dividing layer does not exceed 5-7 microns, which provides a high specific output fragments. The inner surface of the pipe is cooled by flowing water, which provides heat removal during operation channel in a nuclear reactor. Fissile layer enclosed in a sealed metal shell connected to the gas circuit. The fuel channel is placed in the active area or the reflector of a nuclear reactor, in which the support conditions of the reaction of fission. In the fission reaction of uranium-235 in the gas gap between the fissile layer and the metal shell of the fuel channel are received shrapnel elements. The majority of fragments, which is non-volatile refractory metals, metalloids or alkaline earth elements, deposited on the surface of the structure of the fuel channel. The exception catabrosa condition, accumulate in the gap between the fuel and the wall of the channel. A stream of inert gas, for example helium or argon, it is removed from the active zone of the reactor and sealed path through the filtration system are directed to the amount of prior exposure, where the krypton-89 clear of concomitant krypton-90 due to the natural decay of the latter, giving a long-lived radioisotope strontium-90, and then the krypton-89 is sent to the recovery system, where it remains up to the complete collapse in the target radioisotope strontium-89. Evaporative system is a set of gas traps, which is sufficient for accumulation of krypton in several tens of minutes. The resulting decay of krypton-89 radioisotope strontium-89 is removed from the transport of inert gas through adsorption in the coal trap or chemical interaction in an acid environment. Cleared from the target radioisotope transport of inert gas recycle to the reactor core. After removal from the system capture the radioisotope strontium-89 is subjected to final radiochemical purification and translate into marketable form.

As an example of the implementation of the proposed method consider the following options SS="ptx2">

Reactor core "IL-8" consists of 16 fuel assemblies type IRT-3M. The length of the active part of the fuel assemblies 58 cm, the content of uranium to 90 g, and its enrichment - 90% 235U.

The side surface of the active area is surrounded by layers of metallic beryllium thickness of 30 cm, with removable inner layers. The use of beryllium to reduce the amount of the active zone and get in the reflector maximum density of neutrons.

The main parameters of the reactor IR-8": 8 MW; the surface area of heat transfer of 21.9 m2; average heat load 344 kW/m2; the water temperature at the input (output) from the active zone 47,5 (54,5)oWith; the amount of the active zone 47,4 l; weight235U in the active area of 4.35 kg; maximum density of thermal neutron flux of 1014neutrons/(cm2(C): in the active zone is 1.5, in water-filled holes removable beryllium reflector blocks is 2.5.

The metal channel is made of stainless steel OHNT containing cylindrical tubular fuel cell (SOFC), on the outer surface of which is coated with a layer of metallic uranium-235 90% enrichment, connected to the gas circuit, are placed instead of one of the fuel assemblies in aktivitelerini water reactor, pumped through the internal volume of TE. Coolant temperature 50oC. Transportation of gaseous products containing radioactive krypton-89, outside of the reactor is carried out using argon. The gas flow rate is about 1 l/min Gas circuit is equipped with a system of aerosol filters containing material FRR-17-1.5, filters FMSI to trap radioactive isotopes of iodine. On tight loop gas stream is served in a metal container, in which it held until the complete decay of krypton-90, the predecessor of the impurity of the radioisotope strontium-90. Then the gas flow is directed to the recovery system for the final extracts for 30 minutes until complete decay of krypton-89. After cooling in the heat exchanger argon recycle in the fuel solution.

Example 2. A loopback device in the reactor facility "Ruslan".

As the base of the reactor, which can be implemented new technology of production of fission radioisotope strontium-89, selected special reactor "Ruslan" pool-type reactor of the type P-1, intended for the production of radioisotope products General values.

Reaktorkerne active zone;

system control and protection;

- security;

The reactor R-1 is placed in the open top metal casing. The reactor core is submerged in a pool of water and is cooled by the flow of water passing through it in top - down direction. The driving pressure is created by the water column above the active area.

Active area recruited from the workers and specialized tapes and cassettes CPS (with control rods and emergency protection rods). Into the internal cavity of the cassettes are Central build with blocks for producing specialized and commercial radioisotope production.

On the periphery of the active zone, on its perimeter, is three-row radial screen for useful use of lateral leakage of neutrons from the core. All cassettes are arranged in the active area and the screen on a triangular grid with step 125 mm

The business and specialized, as well as cassettes CPS consists of four concentrically arranged hexagonal fuel elements with a height of the active part of about 1000 mm Outer size cassette turnkey is 121 mm All the fuel cartridge is made without the outer cover.

Centralita Central cavity serves for installation of the Central Assembly, and in the cassette cor - siting regulatory or emergency core.

In Fig. 1 shows a diagram of a gas circuit for producing Sr-89 in the reactor "Ruslan", where 1 is the active area; 2 - irradiating device; 3 - valve; 4 - delay line; 5 - filter; 6 - ventilator; 7 - valve; 8 - device deposition of strontium; 9 - valve; 10 - filter; 11 - gate. The reactor loop is a closed pressurized loop, which includes the irradiation device, piping, valves, filters, ventilator and other technological elements. The procedure is the following.

After the reactor is at power and open the valves 3, 7, 9 and 11 and turns on the ventilator 6. Transport of inert gas, passing the irradiation device 2 enters the delay line 4, the function which performs the tube, and a discharge gas from the irradiation device. The purpose of the delay line is to hold the gas before entering the deposition device 8 for a time sufficient for the decay of krypton-90 - predecessor of the main impurity element strontium-90, to acceptable, from the point of view of medical requirements level.

The length, the diameter of the discharge tube and the gas flow rate is determined from the condition abesalom the drug should not exceed 210-4%. For example, when the gas flow rate of 0.2 l/min, time delay 10 min and the internal tube diameter 10 mm length of the delay line will be 26 PM

Not settled in the delay line 4 isotopes of rubidium and strontium are caught on the filter 5. After passing the filter, the gas enters the device deposition of strontium-89 8. The time required for decay of krypton-89 in the target radioisotope, is ~ 15 minutes is Not deposited in the deposition device 8 isotopes of rubidium and strontium are caught on the filter 10, and the gas is returned to the reactor.

After the end of the cycle developments strontium-89 valves 7 and 9 are closed. Deposited in the deposition device 8 and the filter 10 strontium-89 is removed by a specially developed technology.

In Fig. 2 shows a schematic irradiation device for producing Sr-89 in radial screen, where 1 - casing; 2 - gas supply; 3 - gas outlet; 4 - body irradiator; 5 - Nickel filter; 6 - TVEL; 7 - displacer. The irradiation device is placed in the casing 1, having the form of a hexagon with the size of the "turnkey" 121 mm On the outer surface of a fuel rod 6 on the length of 800-900 mm galvanised layer of uranium-235 90% enrichment, a thickness of 5 μm. At a distance of 15 mm from the uranium layer is Nickel filet for filing in the gap between the fuel rod 6 and the filter 5 transport gas argon, washed fissile layer. Passing through the filter 5, argon purged from the non-volatile fission products. Together with the argon is transferred krypton-89 at delay line device in the deposition gas circuit for producing Sr-89, shown in Fig. 1.

In Fig. 3 shows an irradiation device for producing strontium-89 in the reactor core, where 1 is the gas outlet; 2 - gas supply; 3 - medium pipe; 4 - screen absorber; 5 - fuel rod; 6 - body irradiation device. The diameter of the outer body irradiation device 6 80 mm On the outer surface of a fuel rod 5 on the length of 800-900 mm applied layer of uranium-235 90% enrichment, a thickness of 5 μm. Further along the radius of the irradiation device is a wall of a fuel rod 5. In the gap between the fissile layer and the wall of the fuel rod transport is served argon gas, washer fissile layer. Together with this gas is transferred krypton-89 at delay line device in the deposition gas circuit for producing Sr-89, shown in Fig. 1. Sinter filter is the output gas stream from the reactor core, and Fig. 3 is not shown.

The proposed method of producing the radioisotope strontium-89 allows more than one thousand times in comparison with the method, is the most common nuclear research reactors with a thermal spectrum neutrons.

1. The method of producing radioisotope Sr-89, including irradiation with neutrons in a nuclear reactor target containing fissile material, and subsequent removal from the target the target of the radioisotope, characterized in that the target perform with a thickness of fissile layer, providing the ability to exit from the surface of the fission fragments at the expense of the energy of recoil nuclei, fission fragments are removed from the zone output flow of the inert gas stream is fed to the filter area, separate aerosol particles, direct the flow into the volume of the pre-exposure, fragmentation of gaseous Kg-89, which is the predecessor of the Sr-89 in the decay chain fission elements with atomic mass 89, separated from other radioisotopes due to their more rapid natural decay, then send Kg-89 in the recovery system, which can withstand Kg to a complete collapse in the target radioisotope Sr-89.

2. The method according to p. 1, characterized in that as the fissile material used uranium-235, and/or uranium-233, or plutonium-239.

3. The method according to p. 1, wherein filtering the gas stream passing through the exercise of multilayer metal-ceramic filters with temporiti selective structure-based Nike fission elements from the reactor core provide a flow of helium.

 

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