Energy Sources - Nuclear - Fission

Fission

Nuclear power stations use nuclear fission to generate energy by the reaction of uranium-235 inside a nuclear reactor. The reactor uses uranium rods, the atoms of which are split in the process of fission, releasing a large amount of energy. The process continues as a chain reaction with other nuclei. The energy heats water to create steam, which spins a turbine generator, producing electricity.

Stated estimates for fission fuel supply at known usage rates vary vastly, from several decades to billions of years; among other differences between the former and the latter estimates, some assume usage only of the currently popular uranium-235, and others assume the factor of a hundred fuel efficiency increase which would come from utilizing uranium-238 through breeder reactors. The Earth's crust contains around 40 trillion tons of uranium and 120 trillion tons of thorium, but, depending on assumptions, reserve figures can be millions of times less for the portion assumed affordable to extract in the future, for the amount of quality ores of far above average crustal concentration.

At the present rate of use, there are (as of 2007) about 70 years left of presently inventoried uranium-235 reserves identified as economically recoverable at the current natural uranium price of US$130/kg. (For any typical element, though, the amount of proved reserves inventoried at a time may be considered "a poor indicator of the total future supply of a mineral resource"; among examples with other elements, tin, copper, iron, lead, and zinc all had both production from 1950 to 2000 and reserves in 2000 much exceed world reserves in 1950, which would be impossible except for how "proved reserves are like an inventory of cars to an auto dealer" at a time rather than the total affordable to extract in the future).

The nuclear industry argues that the cost of fuel is a minor cost factor for fission power; if needed, more expensive, more difficult to extract sources of uranium could be used in the future, such as lower-grade ores, and, if prices increased enough, from sources such as granite and seawater. Increasing the price of uranium would have little effect on the overall cost of nuclear power; a doubling in the cost of natural uranium would increase the total cost of nuclear power with typical present reactors by 5 percent (without considering usage of breeder reactors for handling greater uranium price rise). On the other hand, if the price of natural gas was doubled, the cost of gas-fired power would increase by about 60 percent.

Opponents on the other hand argue that the correlation between price and production is not linear, but as the ores' concentration becomes smaller, the difficulty (energy and resource consumption are increasing, while the yields are decreasing) of extraction rises very fast, and that the assertion that a higher price will yield more uranium is overly optimistic. As many as eleven countries have depleted their uranium resources, and only Canada has mines left that produce better than 1% concentration ore. Some state uranium from seawater is dubious as a source.

Nuclear meltdowns and other reactor accidents, such as the Fukushima I nuclear accident (2011), Three Mile Island accident (1979) and the Chernobyl disaster (1986), have caused much public concern. Research is being done to lessen the known problems of current reactor technology by developing automated and passively safe reactors. Historically, however, coal and hydropower power generation have both been the cause of more deaths per energy unit produced than nuclear power generation.

Nuclear proliferation is the spread of nuclear technology which may happen from nation to nation or through other black market channels, including nuclear power plants and related technology including nuclear weapons.

The long-term radioactive waste storage problems of nuclear power have not been solved. Several countries have considered using underground repositories. Nuclear waste takes up little space compared to wastes from the chemical industry which remain toxic indefinitely. Spent fuel rods are now stored in concrete casks close to the nuclear reactors. The amounts of waste could be reduced in several ways. Both nuclear reprocessing and breeder reactors could reduce the amounts of waste. Subcritical reactors or fusion reactors could greatly reduce the time the waste has to be stored. Subcritical reactors may also be able to do the same to already existing waste. The only long-term way of dealing with waste today is by geological storage.

At present, nuclear energy is in decline, according to a 2007 World Nuclear Industry Status Report presented by the Greens/EFA group in the European Parliament. The report outlines that the proportion of nuclear energy in power production has decreased in 21 out of 31 countries, with five fewer functioning nuclear reactors than five years ago. There are currently 32 nuclear power plants under construction or in the pipeline, 20 fewer than at the end of the 1990s.

Thorium can be used as fuel in a nuclear reactor. One of the early pioneers of the technology was U.S. physicist Alvin Weinberg at Oak Ridge National Laboratory in Tennessee, who helped develop a working nuclear plant using liquid fuel in the 1960s. A thorium fuel cycle offers several potential advantages over a uranium fuel cycle including much greater abundance on Earth, superior physical and nuclear properties of the fuel, enhanced proliferation resistance, and reduced nuclear waste production. Nobel laureate Carlo Rubbia at CERN (European Organization for Nuclear Research), has worked on developing the use of thorium as an alternative to uranium in reactors. Rubbia states that a tonne of thorium can produce as much energy as 200 tonnes of uranium, or 3,500,000 tonnes of coal. In event of a thorium fuel cycle, even common granite rock with 13 ppm (0.0013%) thorium concentration (just twice the crustal average, along with 4 ppm uranium) contains potential nuclear energy equivalent to 50 times the entire rock's mass in coal, although there is no tendency to resort to such very low-grade deposits as long as much higher-grade deposits remain available and cheaper to extract.