<![CDATA[The production of high-purity ¹⁷⁷Lu via the direct (n,γ) route is highly dependent not only on isotopic enrichment of the target material but also on the strategic selection of encapsulation materials to reduce radionuclidic impurities. In order to optimize the production of high-specific-activity ¹⁷⁷LuCl₃, this work combines a double-layer containment system consisting of quartz ampoules (SiO₂) and high-purity aluminum capsules (Al 1070) with an enriched Lu₂O₃target (74% ¹⁷⁶Lu). Irradiation was performed in the RSG-GA Siwabessy reactor (BRIN, Indonesia) at a thermal neutron flux of 2 × 10¹⁴ n·cm⁻²·s⁻¹ for 99 and 193 hours. The target was dissolved in HCl/H₂O₂to form ¹⁷⁷LuCl₃and then characterized for radionuclidic purity using high-resolution gamma spectrometry (HPGe) at 48 hours post-end of irradiation (EOI). The results exhibit that this integrated system produces products without detectable container-derived radionuclidic impurities at 48 h post-EOI: activation products from the quartz (¹⁹O, T½ = 26.47s; ³¹Si, T½ = 2.62 h) and aluminum (²⁸Al, T½ = 2.24 min) containers decayed completely within 24 hours. Under normal HPGe conditions, the metastable isomer ¹⁷⁷ᵐLu (T½ = 160.4 d, σ = 2.85 barn), the sole co-produced radionuclidic species, is present at <1% of total activity at EOI, is not detected spectroscopically from initial state of ¹⁷⁷Lu, which can be clinically negligible during the typical therapeutic window (1–14 days post-production). The specific activity obtained was 11 718 mCi/mg (CV = 5.9%) after 193 hours of irradiation, a level adequate for effective radiolabeling of monoclonal antibodies and peptides in targeted radionuclide therapy, despite the presence of stable Lu carrier. This study demonstrates that the interaction between target chemistry and container physics, rather than irradiation parameters alone, is a critical determinant in producing pharmaceutical-grade ¹⁷⁷Lu that meets international radionuclidic purity standards (>99.9%). This approach provides a scalable, separation-free production model applicable to medium-flux research reactors globally.]]>
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