"People think of uranium as the main naturally occurring radioactive element, and as the element largely responsible for the internal heat of the earth. But thorium is just as common if not more so. There was even research conducted into making nuclear power plants that ran on thorium rather than uranium fuel, though it didn't work out in the end."

There's a lot of research into thorium breeder reactors going on right now. Thorium-232 will absorb slow neutrons to produce uranium-233, which has somewhat similar properties to uranium-235 (used in conventional pressurized water reactors). India is especially pushing this technology, since they have 4 times as much thorium as uranium in reserves. Their first thorium research reactor went critical in 1996. Worldwide, a number of designs are in development. You're probably thinking of the US attempt in the Shippingport Atomic Power Station from 1977 to 1982 - it was actually a success (there was 1.3% more fissile material when they removed the rods than when they inserted them, after it generated 2.5 billion watts of power), but the reactor wasn't designed to be mass produced, and there was no follow through.

Thorium breeders have interesting potential not only to provide another fuel source many times more abundant than U-235 (which comprises only 0.7% of raw uranium), but also because of anti-proliferation qualities. Anti-proliferation thorium breeders use uranium enriched to about 20% (i.e., not enough to use in a uranium bomb) mixed in with a majority of thorium. Since the uranium is a relatively small percentage, the plutonium bred from the U-238 isn't as much of a proliferation risk as in a normal reactor, and the U-233 never becomes concentrated enough to pose a risk. Thorium reactors also don't produce much waste.

My favorite reactor design is still the Russian BREST reactor. It's a lead/bismuth cooled plutonium breeder that circulates heat via natural convection (vs the normal sodium-cooled pump-fed breeders that we used to use - the concept of using molten sodium filled with short-lived radioisotopes in a giant *concrete* building which contains highly radioactive fuel rods just sounds a bit nutty to me ;) And MONJU showed the risks when the sodium leaked and almost ate through the protective steel to the concrete). With BREST, you get high temperature heating (so you can directly split hydrogen from water with the heat if so desired), a nonreactive and self-containing coolant, safety even if all the coolant pumps fail, little built up pressure, and of course, you have a use for all of that U-238 and notably reduced radioactive waste. Nuclear reactor designs have really been advancing, and it's interesting to read about what's being worked on.

In case you're curious, the reason plutonium breeders need to use liquid metal coolant instead of water is because U-238 only becomes plutonium when hit with fast neutrons; the water moderator in light water reactor slows them down. Thorium reactors, on the other hand, use slow neutrons to breed U-233.

- Karen

Hi. I noticed that your Aeschynite sample is from Iveland in Norway. The small community of Iveland is actually famous for their mines and minerals. Here's a folder with some information about a local exhibition. They also have at least 5 mines that are open to the public for a small price, where you can dig for minerals yourself.

hydrogen, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluoride, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chloride, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, bromine, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium palladium, silver, cadmium, indium, tin, antimony, tellurium, iodine, cesium, barium, lanthanum, cerium, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, astatine, francium, radium, actinium, thorium, protactinium, uranium, neptunium and plutonium.