1. Nuclear fission produces heat and no carbon dioxide. 2. Catalytic converters
ID: 303 • Letter: 1
Question
1. Nuclear fission produces heat and no carbon dioxide.
2. Catalytic converters contain expensive trace metals.
3. The stratosphere contains 1000 times less water and 1000 times more ozone than does the troposphere.
4. Ozone is produced photochemically in the troposphere and the stratosphere, but by different reactions.
5. Air temperature decreases with altitude up to approximately 18 km above the earth, and then it increases with altitude up to 50km.
Nuclear fission produces heat and no carbon dioxide. Catalytic converters contain expensive trace metals. The stratosphere contains 1000 times less water and 1000 times more ozone than does the troposphere. Ozone is produced photochemically in the troposphere and the stratosphere, but by different reactions. Air temperature decreases with altitude up to approximately 18 km above the earth, and then it increases with altitude up to 50km.Explanation / Answer
The first self-sustaining controlled nuclear reaction occurred in 1942 in Chicago and it only took 14 years for that entirely new technology to be transformed into an integrated power station at Calder Hall in England. Since then, nuclear power has grown quickly so that, by 2004, it produced 6% of the world's electric power. But it is rather localised; because nuclear power can lead to nuclear weapons, it is difficult for poorer countries to get hold of the technology. Consequently, if you look at the spread of nuclear power, in 2004 there were the three countries of North America, two countries in South America, eighteen in Europe and Eurasia, six in Asia, just one in Africa and none in the Middle East apart from Israel. In total there are 441 commercial nuclear plants in the world with about 30 being constructed.
The principle of nuclear fission is very simple; like fossil fuel power stations, water is heated, turned to steam and then directed to turn turbines which generate electricity. The difference is that the fuel is not burnt to generate the heat. The fuel is uranium-235 which is a radioactive element. When it absorbs an extra neutron (a building block of its atom), it splits into two ('fission' meaning to 'split' or 'cleave' as in 'fissure') and releases energy. If a chain reaction can be initiated, then this continuous heat can be used to produce steam.
There are several problems with nuclear power which could prevent it becoming the answer to our energy fears.
The current R/P ration for nuclear power is about 15 years if we consider suitable high-grade ores. This would drop to three years if we were able to produce all electricity from nuclear. The only way to avoid this is to use fast-breeder reactors which reprocess spent fuel to create more fuel. Unfortunately this fuel is plutonium, one of the most toxic materials known and a basis for nuclear weapons. Few fast-breeders have been constructed and they have been extremely expensive due to the high safety standards needed. Breeder reactors will not become available for large-scale power generation within the next three decades.
It has long been claimed, and still is by many, that nuclear power emits no carbon dioxide, thereby making it a superior choice for future power with the threat of climate change. It is true that the process of generating heat and steam from nuclear materials does not produce carbon dioxide in itself, but to ignore all of the other processes used in nuclear power is either ignorant or disingenuous. It is rather like claiming that a pumped storage hydroelectric plant is a power creator; it is only if you ignore the fact that more electricity is used to pump the water up in the first place than is generated when it falls.
Large amounts of carbon dioxide are emitted during the building and decommissioning of the power plants, and during the mining, refining and enriching of the uranium. Since you can hardly have nuclear power without the plants or the uranium, that carbon dioxide is as much part of the emission from nuclear power as the direct releases from fossil fuels. (To be fair, this also applies to renewable sources since turbines and solar cells have to be constructed, transported and built, and then maintained. But the amount of carbon dioxide emitted is far less than nuclear.)
The other pollutant that is produced by nuclear is, of course, radioactive waste. The waste includes 1,000 tonnes of high- and low-level waste per year per plant, waste that includes parts that remain dangerous for hundreds or thousands of years. Uranium mill tailings can amount to much more. The problem of dealing with this waste has still not been solved.
The disasters at Three Mile Island and Chernobyl created deep-rooted fears in the minds of the public. While the possibility of a plant exploding like a nuclear bomb are virtually nil, and the number of accidents is low, the dangers created by even one accident have far more serious consequences than an accident happening in a fossil fuel or renewable generator.
2)
Catalytic converter production requires palladium or platinum
3) The tropopause marks the end of the troposphere and the beginning of the stratosphere, the atmosphere
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