New life for forgotten fuel

A molten-salt reactor built in the 1960s by nuclear physicist Alvin Weinberg and used for thorium until 1972

A relatively safe and clean form of nuclear energy, first developed and tested in the US in the late 1960s but neglected by the commercial nuclear industry, may be about to gain a new lease of life.

Supporters of reactors based on thorium, rather than uranium, are trying to re-awaken interest in this forgotten chemical element. Thorium should be safer than uranium because thorium reactors would shut down without any human intervention. Nor would they need mechanical cooling systems to remove excess heat, eliminating the possibility of accidents such as Fukushima.

“Not all nuclear power is equal. Thorium is inherently safer,” says Baroness Bryony Worthington, the Labour peer and campaigner for climate change. “It offers very low-cost, sustainable, safe forms of nuclear power.”

Baroness Worthington is patron of the Weinberg Foundation, a new organisation set up to campaign for the development of thorium technology. “It’s a fuel that no one has heard of, that everyone needs to hear of,” she says.

The organisation is named after the nuclear physicist Alvin Weinberg, who pioneered thorium energy in the US in the 1960s. Bob Cywinski, a physicist at the University of Huddersfield, believes thorium may have been ignored at that time because it would not have provided the plutonium useful for nuclear weapons.

“It’s an unfortunate fact that civil nuclear power has always had a link to the military. And thorium does not produce plutonium,” he says.

Cywinski believes it is time to look again at the technology. “Thorium has an energy density far greater than any other element in the periodic table: one tonne of thorium is equivalent to 200 tonnes of uranium. It’s 100 per cent useable; it doesn’t need processing or enriching. It’s an enormous untapped resource,” he says.

Thorium is more abundant than uranium, with enough thorium deposits to power the world for many thousands of years, and it generates much less radioactive waste when burned in reactors. It can even be mixed with waste from conventional reactors to burn it up.

The main obstacle is that the nuclear industry has a huge reactor and fuel infrastructure based on uranium and plutonium. An enormous additional investment would be needed to shift to thorium.

But Baroness Worthington believes we should be planning to start developing the technology now on a modest scale to prove the concept, and then scale up.

She suggests that one of the sites allocated for new nuclear reactors in the UK could be set aside for an innovative thorium project.

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The rare earth rush

A supply “risk list” of the chemical elements used in commerce and industry, compiled by the British Geological Survey, illustrates China’s domination of global production of minerals and metals. China is the leading producer of 27 of the 52 elements and groups of elements listed, including the 17 “rare earths” that have become critical for production in electronics, alternative energy and other high-tech sectors.

This is not primarily a consequence of China’s geological good fortune in having more than its fair share of deposits of these elements, the BGS says. Rather, China kept old mines going and opened new ones – and arranged to import ore from which it could extract rare metals – while the rest of the world neglected to invest in sources of supply.

“There is a risk not because we’re going to run out of these metals ... but because human factors such as resource nationalism could threaten supplies,” says Andrew Bloodworth, BGS head of science and minerals.

Now that the strategic importance of these materials has been recognised – and their price has risen in response to soaring demand – sources outside China are beginning to open up.

“The message from the geology is that there are loads of potential mines for rare earths and other strategic metals,” says Frances Wall, head of the Camborne School of Mines. Two important new mines for rare earths are opening at Mountain Pass in the US and Mount Weld in Australia.

Although the UK has no minable rare earth deposits, it does have a “world class” deposit of tungsten, an essential metal for hardening alloys, which is at the top of the BGS supply risk list. This deposit, at Hemerdon in Devon, was mined during the two world wars. Now Wolf Minerals, an Australian company, is preparing to re-open the mine.

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Diamonds reveal their deep, dirty secrets

Dirty diamonds from the Juina region of Brazil are of little value as gems because their crystals are deformed and they contain mineral inclusions, but some are very precious for scientists studying movements deep within the Earth.

A dirty diamond up from the depths

Analysis of tiny mineral fragments trapped within Brazilian diamonds shows that some have made a remarkable slow-motion journey over many millions of years from the Earth’s surface crust, down as far as 700km within the lower mantle and then back up.

The study, led by scientists at Bristol University and published in the journal Science, shows that the recycling of materials in the crust extends deeper into the planet’s interior than geologists had previously realised.

The range of minerals included in the diamonds could only have originated in the crust immediately beneath the ocean. But the crystal form of the diamonds shows that they must have crystallised under immense pressure at depths of 700km or more.

The carbon that formed the diamonds may once have been organic material – the remains of marine life – that accumulated on the ocean floor. “These super-deep diamonds tend to be really grungy from the gemological viewpoint – beaten up and deformed by their long journey through the Earth’s crust and mantle,” says Michael Walter of Bristol. “But the inclusions are fantastically useful for studying the inaccessible part of the deep Earth.”

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Fathers spread the word

Our “mother tongue” has more to do with the language spoken by our forefathers than by our female ancestors, writes Jonathan Wood.

Research is revealing that language change in prehistoric times occurred when groups of successful men moved into new areas and brought their language with them, say Peter Forster and Colin Renfrew from the University of Cambridge in the journal Science.

Several studies, involving thousands of people in different communities around the world, have compared genetic markers that are transmitted exclusively down the male line from father to son with others that come from the mother. Whether looking at Polynesian, Indian or African tribes – or Vikings who kidnapped British women and took them to Iceland – the studies have found that the genes of the colonising men correlate with the language that ends up being spoken.

As prehistoric Polynesians spread out across the Pacific, for example, they came across existing Melanesian populations. Today, the New Guinean coast contains pockets of Polynesian-speaking areas separated by Melanesian speakers. It is the Polynesian male Y chromosome that follows the pattern of Polynesian speakers, not DNA from the maternal line.

“Prehistoric women may have more readily adopted the language of immigrant males, particularly if these newcomers brought with them military prowess or a perceived higher status associated with farming or metalworking,” says Forster.