Hi gungho,here is an Australian perspective --
Narration
Energy: it's something you normally don't think about. It pours in from the burning of coal, oil and gas, or from hydro-electric dams. And we keep needing more and more of it -- but that means more greenhouse gases. Nuclear power doesn't generate any gases -- but you try and say that in polite company.
Wilson da Silva PTC
It's not every day you hear about a potential solution to the energy problems of the 21st century in a cafe. But I did -- from my friend Andrew.
Dr Andrew Studer, Physicist
Heard about a great new idea the other day; a thing called an energy amplifier. It's like a nuclear reactor driven by a particle accelerator. And the whole point is you can use thorium instead of uranium, and apparently this produces a heap less waste. The thing can never melt down or blow up. And you can actually use it to reprocess plutonium and nuclear waste from old bombs.
Wilson da Silva
Are we talking about a green nuclear reactor here?
Dr Andrew Studer, Physicist
Well, the whole thing is that it uses thorium which you can't do in an ordinary reactor. You don't have to have this particle accelerator driving it to make it work.
Wilson da Silva
And, what, you can turn it off if there's a risk of a meltdown?
Dr Andrew Studer, Physicist
Well, it can't meltdown because you are in complete control of how much energy's going into it in the first place. So there's no way the thing can ever overheat and blow up.
Narration
It sounds too good to be true, doesn't it? But there's a whole community of scientists out there working on this rather novel idea of a thorium reactor, otherwise known as an energy amplifier ... calculating, designing and experimenting. Three prototype reactors are to be built in Spain, and more are on the drawing boards.
Wilson da Silva PTC
It's sort of like a regular reactor, only it uses thorium instead. You know what we really need? We need to see how a regular nuclear reactor works. But it's not like we have that many of them in Australia.
Wilson da Silva PTC
I'm with Dr Sue Town who's a physicist here at the HIFAR reactor at Lucas Heights in Sydney.
Dr Sue Town, physicist
Looking in here you're basically looking at he top of the reactor, 25 uranium fuel elements that we have, various control arms and safety rods that we have,
Wilson da Silva
Ok, so those things in the middle are basically the fuel rods that drive the reactor?
Dr Sue Town
Yes... we've got 25, they're Uranium 235 that have been enriched to 60%, the total weight is 280g per fuel element of Uranium 235 plus 238.
Wilson da Silva
And uranium is what powers most reactors around the world? Whether research reactors or power reactors?
Dr Sue Town
Right. Basically you have a neutron which bombards an Uranium 235 atom which splits the atom which gives rise to further neutrons coming out of the atom and that then produces fission.
Wilson da Silva
That's what causes criticality isn't it, when you get it to the point where there's a chain reaction occurring?
Dr Sue Town
Yes, that's what a reactor's all about, basically producing that and being able to control and maintain it ...
Narration
It's pretty easy really: just pack enough uranium together and a chain reaction occurs. That's criticality. Now this may be a research reactor, but power reactors work the same way: except that the superhot uranium core turns water instantly into steam, driving turbines and generating electricity -- and lots of it.
But they do have their drawbacks: they produce tonnes of radioactive waste that stays dangerous for a quarter of a million years. A byproduct is plutonium, which is great for making nuclear weapons. And there's always the chance, however remote, of a catastrophic meltdown.
Wilson da Siva PTC
Thorium is also radioactive, although not as much as uranium. No matter how much you pour into the core of a reactor, it can never go critical, or 'try to blow up'. So what you do is you heat it up. Not with a microwave oven, but with a particle accelerator. Basically a big particle gun which fires neutrons into the core of the thorium reactor -- to the point where it is tickling criticality.
The only Australian researching thorium reactors is Dr Reza Hashemi-Nezhad of High Energy Physics ...
We're going to try to catch a physicist in is natural habitat ... (knock, knock).
Wilson da Silva
So what is this thing going to look like?
Dr Reza Hashemi-Nezhad
It's principle is very simple. It's made of a big container which is 30 metres deep. It contains a coolant vessel inside which is filled with the lead. We have the fuel here, which is made of thorium. And then this beam of the protons is fired through a tube into the middle of the fuel. And you produce a lot of neutrons, and produce ... nuclear fission and generate energy.
Narration
This is one reactor that ain't ever gonna meltdown. If it tries to overheat, you simply switch off the accelerator ... and the reaction just fizzles out.
And it produces zero plutonium -- so no bombs. The thorium core is so efficient it can even burn old plutonium, as well as nuclear waste, cooking the whole lot into oblivion.
Dr Reza Hashemi-Nezhad
This sub-critical nuclear reactor is the only logical way of burning the plutonium, producing energy, and getting rid of one of the most dangerous substances on the Earth.
Wilson da Silva PTC
Thorium reactors do produce some waste, but not much. (points to pile of toilet rolls) If this was the amount of waste produced by a conventional reactor, a thorium reactor would generate about this much. (pull one out, others collapse) Three per cent.
The good news is, thorium waste is radioactive for only five hundred years. If you think that's long, try a quarter of a million.
Narration
That's how long conventional waste, on average, stays dangerous. But some of it is radioactive for 20 million years.
In a small way, Dr Hashemi-Nezhad is contributing to the design of thorium reactors. He had these samples irradiated at a powerful accelerator in Moscow to try and predict how neutrons might behave in the core of the reactor.
Dr Reza Hashemi-Nezhad This is a joint group: couple of teams from Russia, couple of teams from Germany; in Strasbourg, France; and China and India are involved in this project and are doing different bits of work. The final results will be compared with each other.
When thorium reactors were first suggested in 1989, scientists just couldn't believe such a simple idea would work. As often happens in science, the discovery was always there to be made: it just took someone to see the possibility, and pounce on it.
Dr Reza Hashemi-Nezhad
If you look at it from any angle, it is much safer than existing reactors, and less harmful than even coal-burning power station.
Narration
There are plans for three reactors in Spain by 2005, while American scientists want to build them to incinerate weapons plutonium. If the science holds true, the first power reactors could be on-line within decades. And there's enough thorium in the ground to power the planet for another 4,400 centuries.
Further Information
Dr Reza Hashemi Nezhad
Room 357
High Energy Physics Department
Physics Building, Physics Road
University of Sydney
Rochell Buckland
Public Relations
ANSTO
Lucas Heights NSW 2234
Web Links
A Realistic Plutonium Elimination Scheme With Fast Energy Amplifiers And Thorium-Plutonium Fuel, a report produced by the European Organization for Nuclear Research.
Conceptual Design Of A Fast Neutron Operated High Power Energy Amplifier, also produced by the European Organization for Nuclear Research.
Reactors Coupled With Accelerators paper delivered at a From seminar at JRC - ISPRA seminar on July 2, 1996.
Closing the Fuel Cycle with Accelerator Driven Systems, International Workshop on the Physics of Accelerator-Driven Systems for Nuclear Transmutation and Clean Energy, 29th Sept. - 3rd Oct. 1997, Trento, Italy.
Some Safety and Fuel Cycle Considerations in Accelerator Driven Systems NATO Advanced Research Workshop on Advanced Nuclear Systems Consuming Excess Plutonium, Moscow, Russia, 13-16 October 1996.
Further links see - Accelerator Driven Systems and Thorium: an E-Print and Links Library (last updated 13th May 1998).
Homepage of University of Sydney School of Physics
Background on Carlo Rubbia , the 1984 Nobel Laureate in Physics who has become a key proponent of the ADS system.
MKY
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