How Nuclear Power Work

Mining

Uranium deposits are found in rocks around the world. The two largest producers of uranium are Canada and Australia. Uranium is recovered either by mining hard rock or by in situ leaching (ISL), where dissolved from the orebody in situ, the solution then being pumped back to the surface. If uranium is mined the rock is crushed and then leached to dissolve out the uranium, which is then precipitated out of solution as the uranium oxide U₃O₈, sometimes known as 'yellowcake'

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Conversion, Enrichment and Fuel Fabrication

Most reactors use fuel enriched in the U-235 isotope. The solid uranium oxide from the mine is converted into the gas UF₆, which is then enriched in the U-235 isotope by one of two physical methods of enrichment. Diffusion enrichment, works by exploiting the different speeds at which U-235 and U-238 pass through a membrane. Centrifuge enrichment, works by passing the gas through spinning cylinders, the centrifugal force moving the heavier U-238 to the outside of the cylinder, leaving a higher concentration of U-235 on the inside.


Uranium dioxide pellets are produced from the enriched UF₆ gas. The pellets are then encased in long metal tubes, usually made of zirconium alloy (zircalloy) or stainless steel, to form fuel rods. The rods are then sealed and assembled in clusters to form fuel assemblies for use in the core of the nuclear reactor.

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Electricity Generation

Nuclear reactors produce electricity by heating water to make steam. The steam is then used to drive turbines that generate electricity. In this sense  nuclear power  plants are similar to other thermal power stations, where the heat from burning coal or gas is used to produce stream. A key difference of nuclear reactors is that they don't emit carbon dioxide. A nuclear chain reaction is so-called because when a U-235 atom splits (or fissions) in the reactor's core the neutrons released cause other uranium atoms to also undergo fission. A moderator slows down the neutrons to achieve this. The nuclear reactor uses control rods to ensure that this chain reaction occurs at a controlled rate.

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Used Fuel Management

Used fuel from a nuclear reactor is first stored to allow most of the radiaoactivity to decay. Then it can either be reprocessed to recover the reusable portion, or it may be disposed of directly as waste. In reprocessing, the used f fuel is dissolved and the uranium and plutonium in the used fuel are separated from the waste fission products. Plutonium can then be combined uranium to make Mixed Oxide Fuel (MOX), which can be used in many modern reactors. Reprocessed uranium can be used in new uranium oxide fuel.

No underground facilities have yet been built for used fuel, although several are planned.

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Waste Management

Nuclear wastes range from low level wastes, which contain barely radioactive materials through to high level wastes such as used nuclear fuel that is not destined for reprocessing. Low level waste facilities are already in operation, taking wastes not only from the power generation sector, but also those from nuclear medicine. High level waste is currently kept in storage facilities and will finally be put into specially engineered underground repositories.

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Decommissioning

Nuclear facilities are decommissioned after the end of their operating lives. All nuclear materials, machinery and plant are removed and it is ensured that the site is returned to a state where it can be used for new purposes.

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Transport

Nuclear materials, such as feedstock in the fuel manufacture process, new fuel, used fuel and wastes are transported between nuclear facilities by road, rail and sea in specially designed containers. Care is taken to ensure that this is safe even in accident situations.

Welcome to Nuclear Power

Nuclear power is the use of sustained nuclear fission to generate heat and do useful work.Nuclear electric plants, nuclear ships and submarines use controlled nuclear energy to heat water and produce steam, while in space, nuclear energy decays naturally in a radioisotope thermoelectric generator. Scientists are experimenting with fusion energy for future generation, but these experiments do not currently generate useful energy.

Nuclear power provides about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity. Also, more than 150 naval vessels using nuclear propulsion have been built.

Nuclear power is controversial and there is an ongoing debate about the use of nuclear energy. Proponents, such as the World Nuclear Association and IAEA, contend that nuclear power is a sustainable energy source that reduces carbon emissions. Opponents, such asGreenpeace International and NIRS, believe that nuclear power poses many threats to people and the environment.

As of 2005, nuclear power provided 6.3% of the world's energy and 15% of the world's electricity, with the U.S., France, and Japan together accounting for 56.5% of nuclear generated electricity. In 2007, the IAEA reported there were 439 nuclear power reactors in operation in the world, operating in 31 countries. As of December 2009, the world had 436 reactors. Since commercial nuclear energy began in the mid 1950s, 2008 was the first year that no new nuclear power plant was connected to the grid, although two were connected in 2009.

Annual generation of nuclear power has been on a slight downward trend since 2007, decreasing 1.8% in 2009 to 2558 TWh with nuclear power meeting 13–14% of the world's electricity demand. One factor in the nuclear power percentage decrease since 2007 has been the prolonged shutdown of large reactors at the Kashiwazaki-Kariwa Nuclear Power Plant in Japan following the Niigata-Chuetsu-Oki earthquake.

The United States produces the most nuclear energy, with nuclear power providing 19% of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors—80% as of 2006. In the European Union as a whole, nuclear energy provides 30% of the electricity. Nuclear energy policy differs among European Union countries, and some, such as Austria, Estonia, Ireland and Italy, have no active nuclear power stations. In comparison, France has a large number of these plants, with 16 multi-unit stations in current use.

In the US, while the coal and gas electricity industry is projected to be worth $85 billion by 2013, nuclear power generators are forecast to be worth $18 billion.

Many military and some civilian (such as some icebreaker) ships use nuclear marine propulsion, a form of nuclear propulsion. A few space vehicles have been launched using full-fledged nuclear reactors: the Soviet RORSAT series and the American SNAP-10A.

International research is continuing into safety improvements such as passively safe plants, the use of nuclear fusion, and additional uses of process heat such as hydrogen production (in support of a hydrogen economy), for desalinating sea water, and for use in district heating systems.

Do you think Malaysian also should follow the Germany ?

Germany Takes Nuke-Free Stance After Japan Nuclear Crisis

The decision was prompted by the Japan nuclear crisis, which started when a 9.0 earthquake and tsunami on March 11 damaged several reactors at the Fukushima Daiichi nuclear power plant, leading to a nuclear meltdown and a serious release of radiation. In addition, thousands of anti-nuclear protesters in Germany took to the streets after the nuclear accident in Japan, calling for an end to German reliance on nuclear power.

It will take Germany 11 years to phase out all of its 17 nuclear reactors, although eight of those reactors are already offline and will never be used again as a result of the announcement. The other nine reactors will be phased out gradually, giving Germany time to increase its use of renewable energy from wind, solar and hydroelectric power. Six of the remaining nine reactors will be removed from service no later than the end of 2021, the other three will be taken offline by the end of 2022 at the latest.

http://video.about.com/environment/What-Are-Causes-of-Global-Warming.htm