Complete nuclear reactor units — pressure vessels, moderator systems, and associated primary-circuit components assembled as a reactor — are among the most tightly regulated capital goods in international trade, subject to Nuclear Regulatory Commission (NRC) licensing, Department of Energy oversight, and Nuclear Non-Proliferation Treaty commitments. Export and import of reactor systems require specific NRC authorizations, and 123 Agreements (civil nuclear cooperation agreements) govern the bilateral framework under which transfers occur. Commercial procurement is limited to a small number of specialized vendors and utility buyers, making this one of the lowest-volume but highest-value headings in the machinery classification.

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