Managing Nuclear Waste thru Transmutation and More . . .

Neutron Captures... Wikipedia

A first-of-a-kind reactor system has been set up in Belgium by coupling a subcritical assembly with a particle accelerator. The work is a major step in a program to research advanced waste management.

The equipment, known as Guinevere, is a demonstration model that supports the project for a larger version that will be called Myrrha (Multipurpose Hybrid Research Reactor for High-tech Applications). It was assembled by France's National Centre for Scientific Research and is managed by the Belgian Nuclear Research Centre (SCK-CEN) at Mol, about 50 kilometres east of Antwerp. The overall project is supported by 12 other European laboratories and the European Commission.

Nuclear terminology classifies an item of equipment as in a critical state if the chain fission reaction is self-sustaining and each reaction leads on average to one more. The term supercritical means the number of fissions is increasing, while subcritical means it is decreasing and will therefore dwindle to nothing. _World Nuclear News

Symmetry Magazine: Myrrha Reference Scheme
Dangerous radioactive isotopes with long half-lives can be transmuted to elements with much shorter half-lives, using spallation neutrons. Spallation neutrons are generated when a beam of protons is accelerated into a spallation target. Neutrons, lacking a charge, do not have to overcome the "coulomb barrier", and can be much more readily incorporated into atomic nuclei to transmute one isotope into another.

It should be noted that the initial neutron source will be Deuterium - Tritium collisions. As the project builds steam, it will incorporate the proton beam - spallation target approach to generating neutrons.

Myrrha will be able to produce radioisotopes and doped silicon, but its research functions would be particularly well suited to investigating transmutation. This is when certain radioactive isotopes with long half lives are made to 'catch' a neutron and thereby change into a different isotope that will decay more quickly to a stable form with no radioactivity. If achievable on an industrial scale, transmutation could greatly simplify the permanent geologic disposal of radioactive waste. Myrrha can also be used to test the feasibility of lead fast reactor technology and is seen as complimentary to the Jules Horowitz Reactor, a thermal spectrum reactor under construction in Cadarache, France.

The total cost of Myrrha has been put at €960 million ($1.2 billion), with 40% of this coming from the Belgian government. SCK-CEN is looking to set up an international consortium to ensure additional financing and has completed a memorandum of understanding with the Chinese Academy of Sciences focusing on Myrrha. _World Nuclear News

DLR BLogs: Myrrha CutawayMore details on Myrrha from Science Insider

Several kinds of nuclear fuel cycles are implemented today: most countries chose the so-called once-through cycle which basically considers spent nuclear fuel as waste, whereas others like France, UK, Japan and soon China reprocess their spent fuel to recover the energetically-valuable material Pu (and partially U) to produce Mixed Oxide Fuel (MOX) to be irradiated in a second cycle (a twice-through cycle). None of them allow a complete use of the natural resource; when discharged from reactor, 96% of spent nuclear fuel is still composed of U and Pu which can produce electricity and could be recycled.

Fast reactors

Although U-238 represents 99.2% of natural uranium, it is not fissile. It could be fertilised by neutron capture in order to produce Pu-239 which is fissile, and work with an implementation of Pu multi-recycling. This is however not possible in LWRs since neutron capture of U-238 is not efficient enough and the neutron capture of uneven isotopes of plutonium is high, leading to the formation of minor actinides. On the other hand, fast neutron spectra relatively increase the capture of neutrons by U-238, leading to the formation of plutonium isotopes which are all fissile in such conditions. For example, the ratio of the capture to fission cross sections of Pu-238, Pu-240 and Pu-242 are increased in fast spectra compared to thermal spectra by a factor of 22, 250 and 36 respectively. In conclusion, fast neutron spectra allow the effective consumption of U-238 to produce fissile plutonium isotopes which are subsequently fissioned to produce energy and electricity. Reactors using fast neutrons are hence potentially able to use more than 80% of the natural resources instead of < 1% for LWR. _ Much more including a look at transmutation nuclear waste management at WasteManagementWorld

Fuel recycling and nuclear waste management should be seen as integral to each other. Rather than wasting up to 99% of the energy in nuclear fuel as current LWRs can do, future generations of advanced reactors should be designed to utilise at least 80% of the energy -- thus extending the nuclear fuel supply of the planet by a factor of 80 or more.

Parenthetically, transmutation by the addition of a neutron is supposed to be behind the "cold fusion" or low energy nuclear reaction (LENR) efforts of a number of startup energy companies -- including Andrea Rossi's Leonardo Corporation, Defkalion of Greece, and Brillouin Energy. The methods being used by these startups for converting protons into neutrons is far from clear at this point.

In addition, sub-critical accelerator driven nuclear reactor designs have also been proposed for the use of thorium 232, an abundant fuel which is fertile rather than fissile -- it must be fed neutrons for conversion to fissile U 233, which spontaneously splits into smaller nuclei and more neutrons.

Parts of the above article were taken from an earlier article at Al Fin blog

New Subcritical Thorium Reactor Revolution

GWPF
Somewhere in Cheshire an energy revolution is brewing. Modern nuclear researchers are developing new approaches to safe subcritical reactors, using fertile thorium as fuel. The new reactor designs will be incredibly safe, proliferation resistant, and will produce only miniscule and easily stored amounts of long-lived nuclear waste.

Imagine a safe, clean nuclear reactor that used a fuel that was hugely abundant, produced only minute quantities of radioactive waste and was almost impossible to adapt to make weapons. It sounds too good to be true, but this isn’t science fiction. This is what lies in store if we harness the power of a silvery metal found in river sands, soil and granite rock the world over: thorium.

One ton of thorium can produce as much energy as 200 tons of uranium, or 3.5 million tons of coal, and the thorium deposits that have already been identified would meet the entire world’s energy needs for at least 10,000 years. Unlike uranium, it’s easy and cheap to refine, and it’s far less toxic. Happily, it produces energy without producing any carbon dioxide: so an economy that ran on thorium power would have virtually no carbon footprint.

Better still, a thorium reactor would be incapable of having a meltdown, and would generate only 0.6 per cent of the radioactive waste of a conventional nuclear plant. It could even be adapted to ‘burn’ existing, stockpiled uranium waste in its core, thus enormously reducing its radioactive half-life and toxicity.

...The good news is that, thanks to funding from the Research Councils UK Basic Technology Programme, we’ve taken the first, critical step to making this dream a reality – constructing an incredibly hi-tech, cutting-edge machine with a surprisingly ordinary name: Emma.

Daresbury, the science park where Emma lives in a big, bare building with solid concrete walls more than two feet thick, isn’t especially scenic – it’s overlooked by a power station and stands on the boggy Cheshire flatland between Runcorn and Warrington, at the head of the Mersey estuary.


...Emma is a particle accelerator, the first of an entirely new type. Since the first such machines were built nearly 80 years ago, accelerators – devices that propel beams of electrons, protons or other particles to high speeds – have played a vital role in experimental physics, opening up fresh insights into the origins of the universe and the nature of matter. But most are big and expensive. The best known and biggest of all is the Large Hadron Collider operated by CERN in Switzerland, an underground ring 17 miles in circumference, which cost billions to construct.

Emma is different. She is the world’s first ‘non- scaling, fixed-field, alternating-gradient’ (NS-FFAG) accelerator. In layman’s terms, says Bliss, this means she is a ‘pocket-sized’ machine, the prototype of a new generation that will be significantly smaller and cheaper than its predecessors.

And this is Emma’s special significance. Making particle accelerators affordable means they could be built and used in practical, everyday settings – such as thorium power stations. The key to thorium energy is likely to be the further development of ‘pocket-sized’ machines – precisely the kind of accelerator that looks and behaves like Emma.

... Thorium atoms only start to undergo fissile nuclear reactions and thus to release their energy when they’re bombarded with neutrons, and these would have to be supplied by an external source – ultimately, an accelerator.

‘This means the margin of safety is far greater than with a conventional plant,’ says Cywinski. ‘If the accelerator fails, all that will happen is that the reaction will subside. To stop the reactor, all you would have to do is switch off the accelerator.’
And if hit by an earthquake, he adds, even one as powerful as the one that wrecked Fukushima, a thorium plant would be ‘intrinsically safer’.

‘There’d be some residual radioactivity heating the core, but sustained nuclear fission would simply stop. Everything would cool much faster. You’d be left not with potential catastrophe, but just a heap of molten metal and metal oxides.’

This type of plant – dubbed the Energy Amplifier by the Nobel Prize-winning physicist Carlo Rubbia in 1993, when he patented the basic design – wouldn’t be simple. Because neutrons carry no electrical charge, the magnets in a particle accelerator have no effect on them.

Hence, the way to generate the neutrons necessary to trigger nuclear reactions in thorium would be to build a ‘spallation source’ in the middle of the reactor core. This is a substance – molten lead, for example – which produces neutrons when you fire a beam of protons at it. That beam, in turn, would come from a particle accelerator.

...Last year, ThorEA published a report, Towards An Alternative Nuclear Future, which concluded it should be possible to build the first 600MW power plant fuelled by thorium with three attached ‘pocket-sized’ NS-FFAG accelerators within 15 years, at a cost of about £2 billion – making it highly competitive in relation to fossil-fuel or conventional nuclear alternatives. _GWPF_from_MailOnline

Using "pocket-sized" accelerators to generate spallation neutrons to breed fissile U233 from fertile Th232 might allow for highly scalable and versatile reactor designs, which would certainly be safer than any nuclear reactors currently generating power. And nuclear is by far the safest form of power generation currently in existence.

Below, you can see researcher Rachael Buckley standing inside the EMMA device.

Thorium itself is plentiful, and will be quite cheap once the infrastructure is developed. The cost for subcritical reactor designs depends mainly on the cost of the accelerators and reactor vessels, and containment. The fuel itself is a negligible expense. And by reducing the quantity of waste to be stored and lowering the proliferation potential of the reactor dramatically, those costs would also plummet.

This technology will also be useful in the perpetual fight against cancer.

‘I’m optimistic we can build a machine that overcomes the technical challenges and would be applicable for cancer therapy straight away,’ he says. ‘I think Pamela can be built for an overall cost of £10-15 million, and would take about five years. And that would be a crucial stepping stone towards a thorium power station. It wouldn’t be cheap. But it would be highly competitive.’

Read more: http://www.dailymail.co.uk/home/moslive/article-2001548/Electron-Model-Many-Applications-Technology-save-world.html#ixzz1P4ubEPYz

It will take time to put the pieces together, but the writing is on the wall, if modern humans will only take the time to read it and take action.

You Can Run Civilisation on Thorium for Hundreds of Thousands of Years and It's Essentially Free

"Once you start looking more closely, it blows your mind away. You can run civilisation on thorium for hundreds of thousands of years, and it’s essentially free. You don’t have to deal with uranium cartels," he said.

Thorium is so common that miners treat it as a nuisance, a radioactive by-product if they try to dig up rare earth metals. The US and Australia are full of the stuff. So are the granite rocks of Cornwall. You do not need much: all is potentially usable as fuel, compared to just 0.7pc for uranium. _Telegraph

NBF

A sub-critical nuclear reactor is far safer than a conventional reactor, but it will only work when fed neutrons from the outside. In the case of the sub-critical Rubbia reactor design discussed below, the outside neutrons are provided via "spallation." The entire process is completely controllable, and thus safe.

...work by Nobel laureate Carlo Rubbia at CERN (European Organization for Nuclear Research) on the use of thorium as a cheap, clean and safe alternative to uranium in reactors may be the magic bullet we have all been hoping for, though we have barely begun to crack the potential of solar power.

Dr Rubbia says a tonne of the silvery metal – named after the Norse god of thunder, who also gave us Thor’s day or Thursday - produces as much energy as 200 tonnes of uranium, or 3,500,000 tonnes of coal. A mere fistful would light London for a week.

Thorium eats its own hazardous waste. It can even scavenge the plutonium left by uranium reactors, acting as an eco-cleaner. "It’s the Big One," said Kirk Sorensen, a former NASA rocket engineer and now chief nuclear technologist at Teledyne Brown Engineering.

...The Norwegian group Aker Solutions has bought Dr Rubbia’s patent for the thorium fuel-cycle, and is working on his design for a proton accelerator at its UK operation.
Victoria Ashley, the project manager, said it could lead to a network of pint-sized 600MW reactors that are lodged underground, can supply small grids, and do not require a safety citadel. It will take £2bn to build the first one, and Aker needs £100mn for the next test phase.

...A few US pioneers are exploring a truly radical shift to a liquid fuel based on molten-fluoride salts, an idea once pursued by US physicist Alvin Weinberg at Oak Ridge National Lab in Tennessee in the 1960s. The original documents were retrieved by Mr Sorensen.
Moving away from solid fuel may overcome some of thorium’s "idiosyncracies". "You have to use the right machine. You don’t use diesel in a petrol car: you build a diesel engine," said Mr Sorensen.

Thorium-fluoride reactors can operate at atmospheric temperature. "The plants would be much smaller and less expensive. You wouldn’t need those huge containment domes because there’s no pressurized water in the reactor. It’s close-fitting," he said.
Nuclear power could become routine and unthreatening. But first there is the barrier of establishment prejudice.

... _Telegraph_via_NextBigFuture

More on the Rubbia "energy amplifier" here and here (PDF)


H/T NextBigFuture

Super-safe Sub-critical Reactors Driven by Accelerator

If you pump neutrons into a subcritical fissionable fuel assembly to create fission, you can control the fission reaction -- analogous to controlling the speed of an internal combustion engine with a carburetor or metered fuel injectors.

Brian Wang has a lot more information on this approach, and other fascinating new approaches to nuclear power. Apparently the cost of pumping neutrons has dropped considerably with the coming of cheaper superconducting particle accelerators for generating proton beams -- which generate spallation neutrons.

Eventually the neutron source for these reactions will come from fusion reactors, but for now the idea is to use a linear accelerator to produce spallation neutrons, to drive the sub-critical fuels to fission.

http://nextbigfuture.com/2010/04/molten-salt-based-accelerator-driven.html


Also check out how existing nuclear reactors can be uprated to produce between 20% and 50% more power -- using annular fuel rod technology.