Researchers at the Middlebury Institute of International Studies in California said they made the finding while investigating a mountain site outside the city of Leshan in the southwest Chinese province of Sichuan, where they suspected China was building a reactor to produce plutonium or tritium for weapons.

Instead, they concluded that China was building a prototype reactor for a large warship. The project at Leshan is dubbed the Longwei, or Dragon Might, Project and is also referred to as the Nuclear Power Development Project in documents.