Everything you need to know about nuclear

The twin disasters of a natural catastrophe and a nuclear crisis in Japan have raised plenty of questions about nuclear energy, many of which have been met with blind emotion, or left unanswered.

To help you make your own mind up about this issue, Business Spectator has compiled a guide to the situation in Japan, radiation and radioactivity, next-generation uranium plants and their alternatives.

An invisible threat

Esther Inglis-Arkell from tech site Gizmodo explains:

"At least one of the explosions at the nuclear power plants has vented steam that contains radioactive materials. The nuclear power plant produces energy by fission of uranium-235, the split of uranium-235 into smaller atoms. Two types of these atoms, cesium-137 and iodine-121 were found about 100km from the Fukushima Daiichi power plant. These radioactive materials can't be detected biologically, and so can be rubbed on the skin, eaten, or breathed in. These atoms break down into even smaller atoms, or their neutrons can change to protons. When this happens, they give off highly energetic gamma rays.

... Gamma rays travel like any other electromagnetic waves – cutting a fairly straight line through world. They can move through a vacuum, or through air or water. They can also cut through light elements like aluminium or most metals. Lead can cut down on gamma radiation, but it can't really stop it. One inch of lead will cut any amount of gamma radiation by half. Another inch will cut it by another half, and so on, and so on. Practically speaking, a few feet of lead will weed out pretty much any gamma radiation, but technically nothing can block all gamma rays from coming through.

Radioactive materials are also tough to contain. Although they can be measured, and scrubbed off, they are tiny, invisible atoms. Once they are released into the air, they can get blown by the wind or rain down on the land, get absorbed or eaten by plants and animals, adhere to matter, and scatter out through the world."

The radiation risks

According to the New York Times:

"The American Embassy recommends Americans within 50 miles (80km) of the Fukushima reactors evacuate, based on an analysis by the Nuclear Regulatory Commission. The recommendation was based on a model that predicts potential radiation levels depending on whether the containment vessels remain intact, weather patterns, and other factors. Here are the results of the model:

Nearly 2 million people live within 50 miles of the plant. This is a much larger area than that established by the Japanese, who have told everyone within 12 miles to evacuate and those between 12 and 19 miles to take shelter."

Disposing of the danger

Matthew L Wald writes in the New York Times:

"The international consensus is that eventually, reactor wastes will have to be buried. The United States plans to do that with all spent reactor fuel, and that includes the rubble from the core at Three Mile Island, which suffered a partial melt-down in 1979. It is sitting in containers at the Idaho National Laboratory, near Idaho Falls.

In the shorter term, the cores from Fukushima are also likely to go into containers, steel cylinders filled with inert gas and then sealed and placed into concrete silos. Such 'dry cask storage' can keep reactor wastes isolated for decades, with minimal requirements for inspection, and no moving parts.

The Japanese 'recycle' some of their fuel, chopping it up, dissolving it in acid, and then using a chemical separation process to leach out the plutonium that was created by the reactor's operation. The plutonium is then formed into new fuel. The remaining materials can be embedded in glass. That could also happen to the reactor core rubble from Fukushima. But those wastes, too, will probably eventually be buried."

Disaster-proofing reactors

Gizmodo's Rachel Swaby explains:

"When world's most advanced operational reactors, called the third generation, are pitted against the direct impact of a jetliner, the structure wins … They fare better in earthquakes, too, and have streamlined systems that make them less susceptible to operational issues like the ones plaguing the Tokyo Electric Power Company.

... China is currently invested in the AP1000 reactor, which is considered Gen III , or the honours class version of these new energy plants. In an event that a coolant pipe bursts, this reactor takes care of the problem without needing operator intervention, pumps, or ac power. If the temperature gets too high, gravity funnels water in from a cooling from a tank above the reactor. It is one of those, as mentioned before, that passively mitigates serious issues.

There are a slew of others that strive for the same. The Kerena, out of Germany, has a core catcher that allows the hazardous nuclear fuel to stay sealed-off and safe from the world in the event of a total meltdown. ACR, currently waiting for certification in Canada, has two independent fast shutdown systems as well as a slew of other passive safety measures. The next decade, if not overwhelmed by current concerns, should see a lot more of these.

At the same time, companies and governments all over the planet are brainstorming the far future. While generation three reactors polish up an older standard, the fourth group of plants will see a total redesign. Uranium will be swapped for the depleted stuff and sodium or helium could replace water as a coolant."

Or is thorium the answer?

Last year, Ambrose Evans-Pritchard gave thorium a spirited tick in London's Telegraph newspaper:

"Nobel laureate Carlo Rubbia says a tonne of the silvery metal 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 burns the plutonium residue 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.

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 0.7 per cent for uranium.

... The Norwegian group Aker Solutions has bought Dr Rubbia's patent for an accelerator-driven sub-critical reactor, and is working on his design for a thorium version 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 £2 billion to build the first one, and Aker needs £100 million for the next test phase.

... 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 pressurised water in the reactor. It's close-fitting,' Ashley said."