THE FUTURE OF ISOTOPE PRODUCTION ON MEDIUM AND HIGH ENERGY PROTON BEAMS

摘要

The production of radionuclides on medium and high energy proton beams for medicine and other applications is an important direction of nuclear chemistry and industry. A number of radionuclides were produced in the past and are produced now at different facilities (LANL, BNL, TRIUMF, INR, iThemba, ARRONAX) on high current beams of protons of incident energies 66-800 MeV. The primary radionuclide is ~(82)Sr (T_(1/2)=25.5 d) which is used for preparing the generator of the shortlived daughter ~(82)Rb (T_(1/2)=1.3 min) applied in cardio diagnostics with PET in North America. Market needs are not satisfied with ~(82)Sr in USA. In addition, growing generator consumption is proposed in Europe and Asia in the near future, and the successful results of ~(82)Rb in oncology will result in a wider application of the generator. The potential for accelerator facilities to produce enough ~(82)Sr is the most critical problem. INR is developing a new facility based on cycling metallic Rb target and on-line Sr-extraction from liquid Rb target by high temperature adsorption. According to the calculations, such facility will be able accept several hundred μA beam and produce at least 3 Ci/day at EOB. This will cover the current and future demands of ~(82)Sr in North America, Europe and Asia. Another radionuclide, which is promising in future and may be produced at medium energy protons is ~(117m)Sn (T_(1/2)=14.0 d). It decays via isomeric transition with the emission of monoenergetic conversion electrons and may be effective for bone cancer diagnostics and therapy, as well as for atherosclerosis therapy. Having a 159-keV γ-line, ~(117m)Sn may be used with widely available SPECT scanners. The technology for no-carrier-added ~(117m)Sn production from Sb-containing intermetallic targets is a mutual development of INR and BNL. Therapeutical a-emitting ~(225)Ac and ~(223)Ra are reasonable to be produced in multi-Curie amounts from Th-target at proton energies 120 MeV and more. Besides the INR accelerator (158 MeV), production at the existing accelerators at BNL, TRIUMF and LANL may also provide high yields of these radionuclides. The direct medical application of ~(225)Ac produced by this method is problematic because of impurities of the longlived ~(227)Ac. However, ~(225)Ac obtained with middle energy protons is prospective for preparation of a ~(225)Ac/~(213)Bi isotope generator.