Nuclear mattersSmall thorium reactors could lead to fossil-fuel-free world within five years

Published 3 September 2010

An argument is made that nuclear reactors which use thorium as an accelerator (hence the technical name: Accelerator Driven Thorium Reactors, or ADTR) could lead to fossil-fuel-free world within five years; thorium is an abundant mineral deposit, with 3 to 5 times more thorium in the world than uranium; more importantly, virtually all of the thorium mined can be used as fuel compared to only 0.7 percent of the uranium recovered in its natural state, this means, in energy terms, that one ton of thorium mined is equivalent to 200 tons of uranium mined, which is equivalent to 3.5 million tons of mined coal; ADTRs also enjoy proliferation resistance advantages compared to other reactor systems

An abundant metal with vast energy potential could quickly wean the world off oil, if only Western political leaders would muster the will to do it. This past weekend Ambrose Evans-Pritchard made a strong case in the Telegraph for thorium reactors as the key to a fossil-fuel-free world within five years, saying the ball is now in President Barack Obama’s court.

Thorium, named for the Norse god of thunder, is much more abundant than uranium and has 200 times that metal’s energy potential. Thorium is also a more efficient fuel source: unlike natural uranium, which must be highly refined before it can be used in nuclear reactors, all thorium is potentially usable as fuel.

Evans-Pritchard says thorium could be used as an energy amplifier in next-generation nuclear power plants, an idea conceived by Nobel laureate Carlo Rubbia, former director of the European Organization for Nuclear research (CERN).

Known as an accelerator-driven system — or, more precisely, the Accelerator Driven Thorium Reactor (ADTR) — it would use a particle accelerator to produce a proton beam and aim it at lump of heavy metal, producing excess neutrons. Thorium is a good choice because it has a high neutron yield per neutron absorbed.

Rebecca Boyle writes that thorium nuclei would absorb the excess neutrons, resulting in uranium-233, a fissile isotope which is not found in nature. Moderated neutrons would produce fissioned U-233, which releases enough energy to power the particle accelerator, plus an excess that can drive a power plant. Rubbia says a fistful of thorium could light up London for a week.

The idea needs refining, but is so promising that at least one private firm is getting involved. The Norwegian firm Aker Solutions bought Rubbia’s patent for this thorium fuel cycle, and is working on his design for a proton accelerator.

Evans-Pritchard says this $1.8 billion (£1.2 billion) project could lead to a network of tiny underground nuclear reactors, producing about 600 MW each. Their small size would negate the enormous security apparatus required of full-size nuclear power plants.

After a three-decade lull, nuclear power is enjoying a renaissance in the United States. The 2005 energy bill included $2 billion for six new nuclear power plants, and this past February, Obama announced $8.3 billion in loan guarantees for new nuclear plants (“U.S. gives loan guarantees for new nuclear power reactors in Georgia,” 18 February 2010 HSNW — but see “Federal loans notwithstanding,