NEW AGE NUCLEAR- THORIUM NUCLEAR REACTOR DESIGNS ADVANCING

FuturePundit, 22 June 2006
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The use of thorium to power nuclear reactors holds out the prospect of a huge reduction in nuclear wastes, a nuclear fuel cycle that is much more proliferation resistant, lower costs, and a fuel that is many times more plentiful than uranium. Australian science writer Tim Dean examines the prospects for thorium reactors in a recent article and finds two avenues of technological advance that might make thorium powered nuclear reactors feasible. The more immediately promising approach uses a mixture of thorium with other radioactive materials.
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The main stumbling block until now has been how to provide thorium fuel with enough neutrons to keep the reaction going, and do so in an efficient and economical way.

In recent years two new technologies have been developed to do just this.

One company that has already begun developing thorium-fuelled nuclear power is the aptly named Thorium Power, based just outside Washington DC. The way Thorium Power gets around the sub-criticality of thorium is to create mixed fuels using a combination of enriched uranium, plutonium and thorium.

At the centre of the fuel rod is the 'seed' for the reaction, which contains plutonium.

Wrapped around the core is the 'blanket', which is made from a mixture of uranium and thorium. The seed then provides the necessary neutrons to the blanket to kick-start the thorium fuel cycle. Meanwhile, the plutonium and uranium are also undergoing fission.

The primary benefit of Thorium Power's system is that it can be used in existing nuclear plants with slight modification, such as Russian VVER-1000 reactors. Seth Grae, president and chief executive of Thorium Power, and his team are actively working with the Russians to develop a commercial product by the end of this decade. They already have thorium fuel running in the IR-8 research reactor at the Kurchatov Institute in Moscow.

The potential to use existing reactors to burn thorium lowers the barrier to use of thorium. Success in existing reactors could catalyze the construction of new reactors designed to use thorium from their start.

He also goes over Carlo Rubbia's proposal to use a particle accelerator to shoot a stream of protons into a thorium reactor.

AN ALTERNATIVE DESIGN does away with the requirements for uranium or plutonium altogether, and relies on thorium as its primary fuel source. This design, which was originally dubbed an Energy Amplifier but has more recently been named an Accelerator Driven System (ADS), was proposed by Italian Nobel physics laureate Carlos Rubbia, a former director of one of the world's leading nuclear physics labs, CERN, the European Organisation for Nuclear Research.

An ADS reactor is sub-critical, which means it needs help to get the thorium to react. To do this, a particle accelerator fires protons at a lead target. When struck by high- energy protons the lead, called a spallation target, releases neutrons that collide with nuclei in the thorium fuel, which begins the fuel cycle that ends in the fission of U- 233.

Governments should accelerate research into new nuclear reactor designs that promise to lower wastes and reduce costs.