Is the “Superfuel” Thorium Risker Than We Thought?

From Popular Mechanics

By Phil McKenna

Imagine a cheap, plentiful source of energy that could provide safe, emissions-free power for hundreds of years without refueling and without any risk of nuclear proliferation. The fuel is thorium, and it has been trumpeted by proponents as a “superfuel” that eludes many of the pitfalls of today’s nuclear energy. But now, as a number of countries including China, India, and the United States explore the potential use of thorium for nuclear power, researchers say one of the biggest claims made about the fuel—its proliferation resistance—doesn’t add up.

“It may not be as resistant as touted and in some cases the risk of proliferation may be worse than other fuels,” says Stephen Ashley of the University of Cambridge. In an article published in the journal Nature online today, Ashley and his colleagues highlight the potential dangers of thorium fuel.

When thorium is irradiated, or exposed to radiation to prepare it for use as a fuel in nuclear reactions, the process forms small amounts of uranium-232. That highly radioactive isotope makes any handling of the fuel outside of a large reactor or reprocessing facility incredibly dangerous. The lethal gamma rays uranium-232 emits make any would-be bomb-maker think twice before trying to steal thorium.

But Ashley and his co-authors say a simple tweak in the thorium irradiation recipe can sidestep the radioactive isotope’s formation. If an element known as protactinium-233 is extracted from thorium early in the irradiation process, no uranium-232 will form. Instead, the separated protactinium-233 will decay into high purity uranium-233, which can be used in nuclear weapons.

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