Research
Accelerator Driven Thorium Reactors
By HSNW 3/9/10
Sep 6, 2010 - 11:34:45 AM

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,

Georgia nuclear power plant faces hurdles,” 22 February 2010 HSNW).

Nuclear plants need fuel, though, which means building controversial uranium mines. Thorium, on the other hand, is so abundant that it is almost an annoyance. It is considered a waste product when mining for rare-earth metals.

Boyle notes that thorium also solves the nonproliferation problem. The Nuclear Nonproliferation Treaty (NPT) prohibits processes that can yield atomic bomb ingredients, making it difficult to refine highly radioactive isotopes. Thorium-based accelerator-driven plants, however, only produce a small amount of plutonium, which could allow the United States and other nations to promote nuclear power without running afoul of the NPT.

Evans-Pritchard says Obama needs a Roosevelt moment, recalling the famous breakfast meeting when Albert Einstein convinced the president to start the Manhattan Project.
Accelerator Driven Thorium Reactor at a glance

How does the ADTR power station work? The ADTR power station uses thorium as its main fuel. As a nuclear material, thorium is not fissile; it is described as “fertile” — which means that by capturing nuclear particles or neutrons it “breeds” or converts to a type of uranium which is able to react in a fission process and produce energy.

In order to provide these neutrons, initially a small amount of material is required along with the use of the accelerator which, through a process known as spallation, provides further neutrons. These spallation neutrons initiate the fission process that goes on to breed further uranium from the thorium.

Aker Solutions says the ADTR power station concept has the following benefits:

* Thorium is an abundant mineral deposit; there being 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. Put simply, in energy terms, one ton of thorium mined is equivalent to 200 tons of uranium mined, which is equivalent to 3.5 million tons of mined coal.
* The concept incorporates intrinsic safety features which are fundamental to its design. A significant advantage of this type of process over conventional reactors is that the accelerator is the main source of reactor control; turn off the accelerator and the reaction reduces virtually instantaneously.
* The ADTR power station has proliferation resistance advantages compared to other reactor systems, specifically long fuel residence time mitigates material diversion, the degree of self-protection afforded by irradiated fuel and no enrichment process is needed. Additionally, there is no requirement for enrichment technology with the thorium cycle.
* Construction below ground means that the reactor is highly resistant to damage from aircraft impact.
* Actinides from a thorium reactor are 0.006 times the amount from a conventional reactor.
* The ADTR power station can be configured as an actinide “burner” reducing long term waste burden.