n 1980, the International Atomic Energy Agency (IAEA) observed that protactinium, a chemical element generated in thorium reactors, could be separated and allowed to decay to isotopically pure uranium 233—suitable material for making nuclear weapons. The IAEA report, titled “Advanced Fuel Cycle and Reactor Concepts,” concluded that the proliferation resistance of thorium fuel cycles “would be equivalent to” the uranium/plutonium fuel cycles of conventional civilian nuclear reactors, assuming both included spent fuel reprocessing to isolate fissile material.
Decades later, the story changed. “Th[orium]-based fuels and fuel cycles have intrinsic proliferation resistance,” according to the IAEA in 2005. Mainstream media have repeated this view ever since, often without caveat. Several scholars have recognized the inherent proliferation risk of protactinium separations in the thorium fuel cycle, but the perception that thorium reactors cannot be used to make weapons persists. While technology has advanced, the fundamental radiochemistry that governs nuclear fuel reprocessing remains unchanged. Thus, this shift in perspective is puzzling and reflects a failure to recognize the importance of protactinium radiochemistry in thorium fuel cycles.
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