iraszl's picture

The Potential Of Thorium As A Nuclear Fuel

Prof Robert Cywinski

A lecture by the University of Huddersfield’s Professor Bob Cywinski inspired a senior figure at the world’s leading science museum to stage an exhibition on safer alternatives to uranium as a source of nuclear power. And it has sparked public debate.

At the Science Museum in London, the gallery named Antenna focuses on contemporary issues in science and technology. Until January 2013 it features an exhibition named Can we get electricity from nuclear waste?

It is based on the case made by Professor Cywinski and his colleagues in favour of thorium as an alternative to uranium and the use of particle accelerators in tandem with nuclear reactors. The result would be safer reactors that produce less waste – and existing nuclear waste could be recycled to generate electricity.

The University of Huddersfield is home to the International Institute for Accelerator Applications, where senior research staff include Professor Cywinski – who is Dean of Applied Sciences – and Professor Roger Barlow, who headed a project at the Science and Technology Facilities Council’s Daresbury Laboratory that created a compact, simple and reliable particle accelerator named EMMA.
This technology would be central to the generation of electricity by thorium-fuelled reactors. A centrepiece of the exhibition at theScience Museum is one of the quadruple magnets from EMMA.

Professor Cywinski in explains the case for particle acceleration: “It removes the need for a chain reaction, making the reactor safer. We don’t have to use uranium. Protons from the accelerator bombard a heavy metal target within the reactor. This knocks neutrons off the heavy metal. These neutrons convert the element thorium into a nuclear fuel and then split its atoms, releasing energy.

“Conventional uranium-fuelled reactors produce highly radioactive waste which can last for thousands of years. Thorium produces far less of this waste. Even better, our reactors could use radioactive waste from conventional reactors as fuel. That means they could supply us with electricity by recycling existing dangerous waste.”

Dr Corinne Burns, who is Assistant Content Developer for Contemporary Science at the Science Museum, explained the genesis of the new Antenna exhibition.

“I attended a public lecture given by Bob Cywinski about the potential of thorium as a nuclear fuel of the future. He described energy amplifier technology. I thought it was a fantastic idea, and that more people should get to hear about it,” she said.

The exhibition has quickly generated interest and debate, according to Dr Burns.

Leading figures from science have responded to the issues raised in the Antenna exhibition. Highly supportive is Professor Jim Al-Khalili, the nuclear physicist and broadcaster: “I’m convinced that thorium reactors would address many of our current concerns about dangerous waste and safety. It will require investment, but the merits of thorium energy need to be considered in relation to subsidies given to renewable energy or the long-term prospects for nuclear fusion research. This energy offers real benefits and a real future.”


AlexC's picture

Good article, but one

Good article, but one misleading statement: "removes the need for a chain reaction" needs correction.

The accelerator-produced neutrons indeed make & fission U233, but the U233 fission also produces neutrons, which can also make & fission more U233 -- there is a chain reaction.

What the statement should say is the reaction is sub-critical, meaning the fuel density and neutron flux in the reactor are insufficient to maintain fission if the accelerator neutron flux is throttled back.

Safety depends on the fuel density and the speed with which the accelerator can be throttled.

This is all good, but the accelerator's power comes from the grid or local generator, so its power saps the output of such a plant. This may be about 20% of net power output, so it's not inconsequential, and it adds to waste heat produced by the plant.

In contrast, safety can be maintained naturally, without power loss, if molten salt fuel is uised -- the natural thermal expansion of the salt reduces fission rate (and breeding rate) when the reactor gets hotter. Thus, liquid salts automatically throttle fission & power to match thermal power removed from the salt when it cycles through a heat exchanger in the power block of the plant.

Liquid salt also provides prompt shutdown via natural drainage to storage, should excessive temperatures occur that are outside the range of thermal feedback above.

If such reactors had been at Fukushima, there would have been no nuclear disaster there. The salt from the ORNL MSRE reactor, shut down in 1969, is still in its underground tank in Tennessee.

Robert Steinhaus's picture

Fluid fueled Thorium LFTRs is

Thorium LFTRs reactors are a good and practical nuclear technology that will produce abundant amounts of inexpensive electricity reliably.

Thorium ADS is an idea the has limited appeal to nuclear engineers, as it adds an expensive and unreliable particle accelerator to an otherwise excellent and serviceable molten salt reactor. If a LFTR really needs a control rod to operate safely we can install one for substantially less than the ~$2 billion dollars it costs to build a large SRF Linear Accelerator. It takes power to operate a large particle accelerator. You have to provide about 1/3rd the output of a standard 1GWe nuclear power plant to supply the energy to operate the size of accelerator needed (and even then the accelerator is so weak and supplies so few spallation neutrons that the Thorium ADS operates at a Kef of ~0.97 - only just under normal reactor criticality having a Kef = 1.

If you want to transmute and burn nuclear waste with your reactor, you are better off selecting a technology that without the slightest exaggeration produces 10^6 times more neutrons than an accelerator to do the job, Thorium PACER. It would take in excess of one hundred Thorium ADS reactors to do the same work as one 1GWe U-233 Ignited PACER Fusion reactor while burning up long half-life Minor Actinides contained in LWR spent nuclear fuel. A 1GWe Thorium PACER also is capable of producing rare U-233 at rates that permit starting ten 1GWe LFTRs a year, better performance than any other current nuclear system of the same size.

U-233 Ignited PACER Fusion is practical fusion power.
For more info -

Robert Steinhaus's picture

Fluid fueled Thorium LFTRs is

An 8GW D-D Fusion PACER reactor is capable of producing 65,000 kilograms of U-233 fuel a year according to Austrian Professor Dr. Walter Siefritz. That would be enough rare U-233 to start eighty-one 1GWe LFTRs a year.
HACER: A Grand Design for Fusion Power by Walter Seifritz

Note: When scaled for standard commercial size of 1GWe, a D-D PACER fusion reactor would produce 8125 kilograms of U-233 per year in PACER fission suppressed breeding blankets inside the PACER cavity. In contrast, a 1GWe (ORNL-3996) MSBR optimized for breeding U-233 without Pa-233 extraction produces about 37 kilograms of U-233 a year. It takes in excess of 21 years for a 1GWe 2-region 2-fluid MSBR without Pa extraction to breed enough U-233 to start one additional 1GWe MSBR.
It is actually easier to create large PACER reactors that produce a high proportion of their energy from fusion (> 99%) when the reactor is larger - like 8GW. It takes high levels of design skill to make small PACER fusion plants around 1GWe output that exhibit high fuel utilization efficiency while producing a high proportion of their energy from fusion.