Researchers in the Netherlands have begun nuclear fission tests using thorium salts – a method said to be far cleaner and safer than uranium-based systems.

Dutch firm NRG has revealed a plan to test small scale reactors that use molten salt as fission fuel, marking the first time scientists have embarked on such experiments since the 1970s.

Experts say thorium is more difficult to weaponize compared to uranium, and could even make for ‘meltdown-proof’ reactors.

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Dutch firm NRG has revealed a plan to test small scale reactors that use molten salt as fission fuel. Inside the Petten test reactor (pictured), where the thorium salt is being tested, fast-moving charged particles cause it to glow

THE 'SAFER' OPTION Experts say thorium is more difficult to weaponize compared to uranium, and could even make for ‘meltdown-proof’ reactors. Thorium is more readily found in nature than uranium, and is not usable by itself in a thermal neutron reactor, as it’s not fissile, according to the World Nuclear Association. But, it is ‘fertile,’ meaning it transmutes to uranium-233 (U-233) when bombarded with neutrons. As Technology Review notes, designs that use thorium in the liquid form would be self-regulating. This means that if they reach excessive temperatures, the primary salt would be drained into dump tanks to prevent an uncontrolled reaction. ‘MSRs have large negative temperature and void coefficients of reactivity, and are designed to shut down due to expansion of the fuel salt as temperature increases beyond design limits,' according to the World Nuclear Association. Advertisement

Thorium is more readily found in nature than uranium, and is not usable by itself in a thermal neutron reactor, as it’s not fissile, according to the World Nuclear Association.

But, it is ‘fertile,’ meaning it transmutes to uranium-233 (U-233) when bombarded with neutrons.

It’s said that the use of thorium in molten salt reactors would produce less toxic waste in the long run, and could be more easily reprocessed.

‘This is a technology with much perspective for large scale energy production,’ said Sander de Groot, of NRG.

‘We want to have a head-start once the technology will break through. We see this as a commercial opportunity for the long-term.’

The first experiment will build off the concept of the waste-burning MSR, or Molten Salt Fast Reactor.

This could, theoretically, be able to use spent fuel from typical uranium fission reactions, according to MIT Technology Review.

The researchers plan to use four ‘crucibles’ containing a mixture of lithium fluoride and thorium fluoride.

These will be placed within concentric steel tubes each roughly 50 cm high, according to Thorium Energy World.

The tubes will then be brought to a radiation field of the High Flux Reactor, where the thorium will then transmute to uranium, which will subsequently begin fission.

Researchers in the Netherlands have begun nuclear fission tests using thorium salts – a method said to be far cleaner and safer than uranium-based systems. The first experiment will build off the concept of the waste-burning MSR. A 'crucible' is pictured on right

The researchers plan to use four ‘crucibles’ containing a mixture of lithium fluoride and thorium fluoride. This container, with salt at the center, is illustrated above

The experiments across several small-scale reactor designs could pave the way for ‘meltdown-proof nuclear power, Technology Review notes, as designs that use thorium in the liquid form would be self-regulating.

‘Safety is high due to passive cooling up to any size,’ the World Nuclear Association explains.

‘Also, several designs have freeze plugs so that if excessive temperatures are reached, the primary salt will be drained by gravity away from the moderator into dump tanks configured to prevent criticality.

‘MSRs have large negative temperature and void coefficients of reactivity, and are designed to shut down due to expansion of the fuel salt as temperature increases beyond design limits.’

It’s said that the use of thorium in molten salt reactors would produce less toxic waste in the long run, and could be more easily reprocessed. A close-up view of the Petten reactor is shown

The researchers plan to stick to standard materials, such as stainless steel, for the experiments, unless it proves unsuitable.

In the tests to follow, they will use a different mixture that contains beryllium, forming what’s known as FliBe.

These will focus on the interaction between the salt and the containment materials.

China has also shown interest in MSR technology, with plans to have thorium-based reactors added to the grid within the next two decades.