Mo Production for Medicine
Development of High-Effective and Low-Waste Technology of Fission-Fragment 99 Mo Production for Medical Purpose Based on Use of Fluoride Molten Salts
Tech Area / Field
- FIR-ISO/Isotopes/Fission Reactors
3 Approved without Funding
Kurchatov Research Center, Russia, Moscow
Project summaryThe use of radioactive nuclides in medical researches spreads widely. On these needs more than 50 % of annual radionuclides production is spent all over the world. At present more than 70 % of diagnostic researches are carried out with help of radionuclide 99mTc generated in decay of 99 Mo. The needs of world market in 99Mo make more than 500 thousand Ci/year and annually grow on 15-20 %.
One of the known ways of 99Mo production is a neutron capture by 98Mo (n,g)99Mo. The advantage of this technology is that the radioactive wastes are practically absent. However it has small productivity, and a received 99Mo is characterized by low specific activity because of presence in final product of isotopic carrier 99Mo.
The second the way of 99Mo production in fission reactor is based on neutron fission of uranium. The high-enriched uranium target is irradiated in fission reactor, and then is radiochemicaly processed for extraction of 99Mo, specific activity of which reaches several tens of kCi per gram of molybdenum. This technology has received a wide distribution. The most complicate problem of fission-fragment molybdenum production is the necessity of disposing of plenty of radioactive wastes, as at uranium fission the wide fission fragment spectrum is formed with the total activity at the end of irradiation exceeding by two order of magnitude the activity of 99Mo.
The purpose of project is the execution of complex experimental and caiculational researches for substantiation of new high-effective and low-waste technology of fission-fragment 99Mo production based on use of fluoride molten salts.
The principal of the proposed technology consists in following. The molten salt fuel on base of fluorides of lithium, beryllium, zirconium and uranium is irradiated in neutron flux of nuclear reactor. The fission-fragment molybdenum, formed as a result of 235U fission, not having steady soluble in fuel salts substances, will flow in gas space over a mirror of molten salt and be there in form of aerosol. The spontaneous separation of molybdenum from molten salt fuel happens. According to experimental data, from molten salt will leave about 50 % of molybdenum. The majority of fission fragments, such as Zr, Ba, Sr, Cs, Br, I, having the steady good soluble in the molted salt complexes, remains in molten salt. Taking this into account, it is proposed to remove fission-fragment molybdenum from gas space over molten salt surface, to catch it and to result in the form, convenient for subsequent use in technetium generators. As the majority of fission fragments and practically whole uranium will remain in fuel salt, in the new technology considerably decreases the quantity of radioactive wastes in comparisons with conventional production of fission-fragment molybdenum, where the output of wastes reaches the tens Ci on 1 Ci of 99Mo.
In frameworks of project it is planned to execute the series of model and life-condition researches of fission-fragment 99Mo formation in molten salt nuclear fuel under neutron irradiation, to study the behavior of molybdenum in fluoride molten salts, to develop the ways of removal of aerosol and molybdenum fluorides from gas phase over a molten salt surface, subsequent its depositing on adsorbents and transferring of radionuclide 99Mo in form, suitable for preparation of 99mTc generators.
The life-condition test of technology of fission-fragment molybdenum production in molten salt nuclear fuel is planned to conduct in the RRC KI research reactors IR-8 or ARGUS.
Main activities of the project
1. The execution of comparative analysis of the modern technologies of 99Mo production from the point of view of economic and ecological perspectives of their further use.
2. The substantiation of advantages of the modern technologies of 99Mo production on the basis of use of molten salt nuclear fuel.
3. The researches of physical-chemical aspects of fission-fragment molybdenum behavior in fluoride molten salts. The determination of its solubility in molten salts of various composition, the chemical form of existence, the rate of removing from fuel composition and depositing on structural materials.
4. The researches by IR-spectroscopic methods of vapor phase over the molten salts for determination of molecular structure of fluorides and aerosols.
5. The execution of calculational researches for substantiation of creation of experimental installation for demonstration of possibilities of the molten salts technology of 99Mo production.
6. Designing and manufacturing of experimental installation.
7. Execution of a complex of calculation studies and of a series of technological experiments for:
- demonstration of serviceability of proposed method of 99Mo production;
- optimization of the way of molybdenum extracting from the gas volume over the molten salt;
- optimization of the way of 99Mo depositing and transformation to commodity form;
- experimental estimation of the given method productivity;
- determination of radionuclide cleanliness of received product;
- determination of composition and amount of radioactive wastes, accompanying to extraction of 99Mo on given technology, and research of opportunity of their utilization.
The received results will give the detailed information about the behavior of fission-fragment molybdenum in molten salts, the ways of its removal from reactor active zone and chemical processing for making its commodity form. In particular the following results are expected.
1. The technology of 99Mo production will be developed based on the unique properties of molten salt nuclear fuel and the features of behavior in it of some fission fragments.
2. The migration rate of fission-fragment molybdenum to the liquid-gas surface in steady state condition and at purging of inert gas through the molten salt.
3. The molecular composition of the gas phase over the molten salt.
4. The balance ratio on distribution of fission-fragment 99Mo between the liquid salt, gas phase and the structural materials surfaces.
5. The efficiency of fission-fragment molybdenum depositing on adsorbents of various structure.
6. The structure and amount of radioactive wastes accompanying the depositing of 99Mo on adsorbents.
7. The experimental estimation of the proposed technology productivity and of radionuclide cleanliness of the product.
8. The technique of mock-up experiment on reception of fission-fragment molybdenum at an installation with isotopic neutrons source.
9. The measurement techniques of:
- spectral structure of gas phase,
- migration of fission-fragment molybdenum in molten salt.
Potential role of foreign collaborators
The cooperation with foreign interested institutions on a project subject in areas of task definition, discussions and uses of activity results is possible.