水溶液ターゲットによる89Zr製造：溶液組成が照射中の化学反応に与える影響
This study investigated a solution-based target approach for producing 89Zr by bombarding aqueous yttrium salt solutions with 14 MeV protons using a niobium target via the 89Y(p,n)89Zr nuclear reaction. While this method reduces the capital and operational costs associated with solid target systems, radiolytic decomposition of water generating molecular hydrogen and oxygen was identified as a critical obstacle. A systematic mechanistic investigation revealed that gas evolution rates varied more than 40-fold depending on solution composition under identical irradiation conditions. Chloride salts showed increasing gas evolution in the order Na < Ca < Y, whereas the corresponding nitrate salts exhibited the opposite trend. Addition of nitric acid to the irradiation solution further suppressed gas formation. Under optimized conditions (2.75 M yttrium nitrate, 1.5 N HNO3, 20 μA for 2 hours), 89Zr was obtained at a moderate yield of 4.36 ± 0.48 MBq/μA·h with high effective specific activity of 464 ± 215 MBq/μg. The authors suggest this nitrate-based approach may be extended to other radiometals including 64Cu, 68Ga, and 86Y.
Proton irradiation induces radiolytic decomposition of water, generating molecular hydrogen and oxygen gas. Nitrate ions and nitric acid act as radical scavengers, suppressing gas evolution and stabilizing the solution target environment.
The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).
See also:
https://h2-papers.org/en/papers/24607433