Study on 99Mo production by solution irradiation method (1). Characterization of aqueous molybdate solutions under unirradiation

The solution irradiation method is proposed as a new production technique for 99Mo, which is the parent nuclide of 99mTc used as a radiopharmaceutical. In this new method, an aqueous molybdenum solution is irradiated with neutrons in a nuclear reactor, and more efficient and lower-cost 99Mo production than conventional 99Mo production can be realized by using the 98Mo (n, γ) 99Mo reaction and the molybdenum adsorbent of PZC. Aiming at the practical application of this method, unirradiation tests, gamma-ray irradiation tests, and neutron irradiation tests should be needed in order to characterize the aqueous molybdenum solution as the irradiation target. In the present study, the schematic structure of the 99Mo production system with the new method was investigated, and two kinds of aqueous molybdate solutions (an aqueous ammonium molybdate solution and an aqueous potassium molybdate solution) were selected as candidates for the irradiation target of the new method, and then the molybdenum adsorption performance of PZC with the solutions, the properties of the molybdates to be materials of the solutions, the compatibility between the solutions and structural materials, and the chemical stability of the solutions were investigated under unirradiation. As a result, it was found that the aqueous potassium molybdate solution is promising as the target in terms of the molybdenum content, the compatibility with the structural materials, and the chemical stability and that the aqueous ammonium molybdate solution with suitable pH adjustment has an aptitude for the target. In addition, it became clear that stainless steel having good compatibility with the solutions has a potential as the structural material of capsules, pipes and so on. (author)