Development of photonuclear technology of medical radionuclides production

Since 50s of the last century it has been known that photonuclear reactions can lead to generation of the most part of known isotopes. For this purpose it was necessary to create an intense 15-25 MeV photon source. At that time (as well as now) photons were usually produced as bremsstrahlung (braking) radiation of high-energy electrons. Efficiency of electron energy conversion into such high-energy photons is usually low and does not exceed 15%. In addition, photonuclear reaction cross-sections are also small. Thus, generation of effective radioisotopes for practical use could be only realized on the basis of powerful high-intensity linear electron accelerators [1], which had not been created at that moment, while more powerful isotope sources, i.e. nuclear reactors were considerably more efficient in production of new nuclei as fission and radiation capture products. Moreover, the development of charged heavy particle accelerators provided a new source for production of radioisotopes. These two methods (nuclear methods) are the basic ways at present in production of radionuclides, and for a long period of time practical use of photonuclear reactions was limited predominantly by activation analysis.

Recent intense interest to photonuclear reactions is determined by realization of a number of new applications. There are following examples of practical application: nuclear waste processing, creation of intense neutron sources, production of radioactive nuclei beams, activation analysis and inspection technology, radiological protection, astrophysical nuclear fusion, etc.

The detailed analysis of photonuclear methods including prospects and problems of the nuclear technology development showed that in some cases photonuclear methods taking into account economic, technical and ecological factors can be competitive with nuclear methods of radioisotopes generation [2, 3]. Issues of these methods usage for production of medical isotopes have drawn attention of researchers in other countries, too. For example, in the middle of 90s in the USA researches were carried out under the guidance of Prof. L.M. Lidsky for study a possibility of commercial production of medical isotopes, in particular 99mTc, with the use of linear electrons accelerator. On the basis of obtained data the conclusion was made that in the USA production of 99mTc by photonuclear method is not competitive with the reactor method. However, production of other radionuclides can be profitable. Subsequent detailed calculations [4] showed that with considerable production volumes and optimization of accelerator settings production of 99mTc can be merchantable in the USA, too. At the same time photonuclear method is more advantageous in terms of ecological cleanness as results in fewer radioactive wastes. In addition, photonuclear technologies unlike nuclear ones are realized on the equipment which can’t be used for weapon manufacture.

In the middle of 90s of the last century wide experience of “Accelerator” S&R Establishment employees and creation of high-intensity acceleration equipment allowed to start researches in the field of use of photonuclear methods for medical isotopes production. Studying the conditions of photonuclear production of medical radioisotopes was the main task of these researches in order to determine the list of the isotopes which production by this method could be commercially effective. This research included not only the determination of conditions for the maximum increase of isotope yield, but also evaluation of production and operation stages.

Much attention was initially focused on research of a possibility for photonuclear production of  under the  reaction, which is the parent isotope for production 99mTc. This problem is the most urgent for Ukraine where there are no production facilities for this important isotope. The results of research showed that under our conditions with the use of existing (or modernized) acceleration equipment we can produce up to several Ku 99mTc (enriched Mo) in the form of sodium pertechnetate during one week cycle [5]. In addition, researches were carried out for a possibility of production of 57Co [6], 186Re [7] and other isotopes.

On the basis of the results of the research carried out by our division, and also the experience of the Russian production engineers [8], we developed the technology of sodium pertechnetate production with the double extraction of 99mТс by methyl ethyl ketone from the solution of metal molybdenum.

To implement this technology the research radiochemical laboratory was created in the “Accelerator” S&R Establishment for work with samples irradiated at electron accelerators, for carrying out research of radioisotope extraction technologies, including medical purpose technologies. The laboratory is a complex of premises and radioprotective equipment which enables the works with open ionizing radiation sources of Class I.

At present the researches are being carried out in “Accelerator” S&R Establishment for getting of necessary nuclear-physical data. Full-scale irradiation experiments are being conducted [9]. Radionuclides 99mTc and 67Cu [10, 11] were chosen for the first stage. The technology of their extraction from the irradiated targets is being developed. It is planned to use KUT-30 accelerator as the basic accelerator for production of radionuclides.

Research and developments in the field of photonuclear methods of medical isotopes production were carried out with financial support from the US Department of Energy and in close contact with a group of American scientists from the Argonne National Laboratory headed by Dave East.

[1] M.P. Zykov, G.E. Kodina. Mo-99 Production Methods // Radiochemistry - 1999, v.41, N.3, p.193-204.

[2] V.I. Nikiforov, V.L. Uvarov. Estimation of Photonuclear Isotope Yield in Production Targets // Radiochemistry - 2010, v.52, N.3, p.268-273.

[3] V.L. Uvarov, N.P. Dikiy, A.N. Dovbnya, Ye.P. Medvedyeva, G.D. Pugachov, Yu.D. Tur. // Proceedings of PAC97 - 1997, p.3840-3841.

[4] R.G. Bennett, J.D. Christian, D.A. Petti, W.K. Terry, S.B. Grover. // Nucl. Technol. - 1999, v.126, N.1, p.102-121.

[5] N.P. Dikiy, A.N. Dovbnya, V.L. Uvarov. Fundamentals of Technological Cycle Technetium-99m Production at Electron Accelerator // Problems of Atomic Science and Technology - 2004, N.1, p.168-171.

[6] N.P. Dikiy, N.A. Dovbnya, O.A. Repikhov, I.N. Shlyakhov, V.L. Uvarov, Ja.N. Kravchenko. Electron Linac Production of Co-57 for Gamma-chamber Calibration // Problems of Atomic Science and Technology - 2001, N.5, p.200-2002.

[7] A.N. Dovbnya, N.P. Dikiy, A.S. Zadvornyi, G.P. Kotin, A.V. Torgovkin, B.I. Shramenko. Production of Isotopes 184Re, 186Re and 188Re at Linear Electron Accelerators of NSC KIPT // Problems of Atomic Science and Technology - 2001, N.5, p.203-205.

[8] M.P. Zykov, V.N. Romanovskiy, D.V. Vester et al. Application of Extraction Generator for Production of Radiopharmaceuticals on the basis of 99mТс // Radiochemistry - 2001, v. 43, edit.3, p.264-266.

[9] A.N. Dovbnya, G.P. Kovtun, A.V. Torgovkin, V.L. Uvarov, B.I. Shramenko. Estimation of Os, Ir, Sc, In Isotope Production at Electron Linear Accelerators // Problems of Atomic Science and Technology - 2006, N.3, (47), p.168-170.

[10] N.I. Aizatsky, E.Z. Biller, V.M. Boryskin et al. Development in NSC KIPT of Photonuclear Technology of Medical Radionuclides Production // Ukrainian Journal of Radiology - 2007, N.2, p.221.

[11] N.І. Aizatsky, N.P. Dikiy, A.N. Dovbnya, Yu.V. Lyashko, O.M. Medvedyeva, V.I. Nikiforov, A.E. Tenishev, A.V. Torgovkin, V.L. Uvarov, V.A. Shevchenko, B.I. Shramenko. Production of Carrier-free Cu-67 at Electron Accelerators // Ukrainian Journal of Radiology - 2007, N.2, p.223.