30 June 2011

What About Thorium?

The raw material, thorium, is much more abundant than uranium and emits only low-level alpha particles. It has one isotope and therefore, does not require an enrichment cycle to be used as fuel. It is many times more energy efficient than uranium.

A thorium reactor produces no plutonium that can be made into atomic weapons and less longer-lived radionuclides than a uranium-based reactor. Because there is no chain reaction, there is no chance of a meltdown. Nuclear waste from past operations that contain fissile uranium and plutonium can be used as start-up fuel. _ResourceInvestor
For humans to enjoy a clean and abundant energy future, they will need to move to energy from nuclear reactions -- which means nuclear fission, for now. Thorium is the main alternative to uranium as a large-scale nuclear fuel. Here are some basic facts about thorium:
Thorium is a naturally-occurring, slightly radioactive metal discovered in 1828 by a Swedish chemist, Jons Jakob Berzelius, who named it after Thor, the Norse god of thunder. The silvery white metal is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium. Typical garden variety soil commonly contains an average of around 6 parts per million (ppm) of thorium.

Thorium oxide, also called thoria, has one of the highest melting points of all oxides at 3300°C. When this oxide is heated in air, thorium metal turnings ignite and burn brilliantly with a white light. Because of these properties, thorium has found applications in welding electrodes, heat-resistant ceramics, light bulb elements, lantern mantles and arc-light lamps. Glass containing thorium oxide has a high refractive index and dispersion and is used in high quality lenses for cameras and scientific instruments.
Sources and geographical distribution
The most common source of thorium is the rare earth phosphate mineral, monazite, which may contain up to about 12 percent thorium phosphate; however, the average is closer to a 6-7 percent range. Monazite is found in igneous and other rocks but the richest concentrations are in placer deposits, concentrated by wave and current action with other heavy minerals. World monazite resources are estimated to be about 12 million tonnes, two-thirds of which are in heavy mineral sands deposits on the south and east coasts of India. Australia is estimated by the USGS to host approximately 24 percent of the world’s thorium reserves. A large vein deposit of thorium and rare earth metals have been discovered in the Lemhi Pass region of Idaho and Montana.
Going nuclear
Although not fissile itself, thorium has started to reemerge as a tempting prospect to employ as fuel in nuclear power reactors. Thorium 232 will absorb slow neutrons to produce uranium 233, which is fissile (and long-lived). The irradiated fuel can then be unloaded from the reactor, the uranium 233 separated from the thorium, and fed back into another reactor as part of a closed fuel cycle. Alternatively, uranium 233 can be bred from thorium in a blanket, the uranium 233 separated, and then fed into the core.
The use of thorium-based fuel cycles has been studied for about 40 years, but on a much smaller scale than uranium or uranium/plutonium cycles. Basic research and development has been conducted in Germany, India, Japan, Russia, the UK and the USA. China and India have been among primary catalysts in research efforts to use it. Test reactor irradiation of thorium fuel to high burn-ups has also been conducted and several test reactors have either been partially or completely loaded with thorium-based fuel.
Thorium can be used in Generation IV and other advanced nuclear fuel cycle systems.
China has been working on developing the technology for sodium cooled fast reactors which are a type of liquid fluoride thorium reactors (LFTRs). The advanced breeder concept features a molten salt as the coolant, usually a fluoride salt mixture. This is hot, but not under pressure, and does not boil below about 1400°C. Much research has focused on lithium and beryllium additions to the salt mixture. In mid-2009, AECL signed agreements with three Chinese entities to develop and demonstrate the use of thorium fuel in the Candu reactors at Qinshan in China. _UraniumInvesting
The best ongoing source for information on thorium energy is Kirk Sorensen's blog "Energy from Thorium".

Kirk is featured in the introductory video below. You can click on the YouTube icon on the video below to watch the vid at YouTube, and to find links to several related videos -- some of them well over an hour in length.

Another blog dedicated to the molten salt reactor is the Nuclear Green blog.

Here's more on thorium, from a piece in Popsci from last summer:
An abundant metal with vast energy potential could quickly wean the world off oil, if only Western political leaders would muster the will to do it, a UK newspaper says today. The Telegraph makes the case for thorium reactors as the key to a fossil-fuel-free world within five years, and puts the ball firmly in President Barack Obama's court.

Thorium, named for the Norse god of thunder, is much more abundant than uranium and has 200 times that metal's energy potential. Thorium is also a more efficient fuel source -- unlike natural uranium, which must be highly refined before it can be used in nuclear reactors, all thorium is potentially usable as fuel. _Popsci

Another basic overview on thorium

An overview of thorium by Wired magazine

Adapted from an earlier article on Al Fin Energy

The US Nuclear Regulatory Commission under the Obama regime has been very unhelpful, in terms of new reactor development and licensing. It is likely that China will develop the first successful molten salt reactor (MSR) using thorium fuel. Mass production of small modular reactors based upon thorium MSRs would give China a significant head start on what is likely to become a huge energy industry.


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Blogger kurt9 said...

Thorium is readily available and comes as a byproduct of several current mining practices. It comes as a byproduct of Rare Earth mining (a mine in CA was shutdown because it was creating too much Thorium waste). It is also abundant in the ash that results from coal power plants. Think of Coal power plants as the first step in processing Thorium for nuclear power plants and you get the idea.

Thursday, 30 June, 2011  
Blogger rbl said...

Your first link is a bit confused about thorium based fission reactors. There is certainly a chain reaction going on; it's just using 233U instead of 235U.

A complication of thorium nuclear chemistry is the tendency toward n,2n reactions. What you'd like to have happen is
232Th + n -> 233Th -> 233Pa -> 233U
233U + n -> (fission products) + ~200MeV

What Nature often gives you is
Th232 + n -> 231Th + 2n;
231Th->231Pa(a nasty long-lived Nwaste)
233U + n -> 232U + 2n
232U and its decay daughters are powerful gamma emitters. Thorium fans claim this bug is actually a feature, as it contaminates 233U so badly it can't be handled as a bomb component.

Kirk Sorenson and other experts are well aware of these problems, but there are too many 'net fanbois that think thorium is some kind of clean miracle fuel. Actually, it will require a major effort in nuclear, chemical, and materials engineering to get it to work.

Monday, 04 July, 2011  
Blogger al fin said...

Thanks for the comments.

You may have misread the article, rbl. Which link specifically do you refer to? None of them seem to make the error you suggest.

No one here is looking at thorium as a magical energy elixir. On the other hand, several decades have been lost which could have been spent developing thorium reactor systems which deftly avoid the inevitable problems one faces with any attempt to cheat mother nature out of large scale energy.

Making up for lost time seems called for.

Monday, 04 July, 2011  
Blogger rbl said...

Your top "resource Investor" link is a geologist, and I wouldn't expect him to be up on nuclear chemistry. He says "Because there is no chain reaction, there is no chance of a meltdown", - well, there is a chain reaction, but the fuel is already melted.

With "fast" neutrons, there is a greater chance of hitting a nucleus and knocking 2 neutrons out, the n,2n reaction.

The nuclear engineer's problem is to design the molten salt components and the graphite moderator to get enough fissions to generate the heat, but minimize the unwanted reactions.

The chemical engineer's problems are chemically stripping the fission products out of the 233U fuel salt, and separating 233Pa and 233U from the 232Th blanket salt.

The Materials engineering challenge is to find metals that can withstand neutron bombardment, high temperature, and attack by fluoride salts.

These are all fairly new technology, and I would expect several generations of prototypes before LFTRs can start to replace other power generators.

Thursday, 07 July, 2011  

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