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Is The Nuclear Option A Viable Option?

Nuclear power supplies a sixth of the world’s electricity.
Along with hydropower (which supplies slightly more than a sixth), it is the major source of “carbon-free” energy today.
The fossil-fuel alternatives have their drawbacks. Natural gas is attractive in a carbon-constrained world because it has lower carbon content relative to other fossil fuels and because advanced power plants have low capital costs. But the cost of the electricity
produced is very sensitive to natural gas prices, which have become much higher and more volatile in recent years. In contrast, coal prices are relatively low and stable, but coal is the most carbon-intensive source of electricity. The capture and sequestration of carbon dioxide, which will add significantly to the cost, must be demonstrated and introduced on a large scale if coal-powered electricity is to expand significantly without emitting unacceptable quantities of carbon into the atmosphere. These concerns raise doubts about new investments in gas- or coal-powered plants. In an open fuel cycle, also known as a once-through cycle, the uranium is “burned” once in a reactor, and spent fuel is stored in geologic repositories. The spent fuel includes plutonium that could be chemically extracted and turned into fuel for use in another nuclear plant. Doing that results in a closed fuel cycle, which some people advocate.
A longer-term option could involve recycling all the transuranics (plutonium is one example of a transuranic element), perhaps in a so-called fast reactor. In this approach, nearly all the very long lived components of the waste are eliminated, thereby transforming the nuclear waste debate. Substantial research and development is needed, however, to work through daunting technical and economic challenges to making this scheme work.

Pros -
1. Little Pollution As demand for electricity soars, the pollution produced from fossil fuel-burning plants is heading towards dangerous levels. Burning coal produces carbon dioxide, which depletes the protection of the ozone. The soft coal, which many power plants burn, contains sulphur. When the gaseous by-products are absorbed in clouds, precipitation becomes sulphuric acid. Coal also contains radioactive material. A coal-fired power plant emits more radiation into the air than a nuclear power plant.
The world's reserves of fossil fuels are running out. The sulphurous coal which many plants use is more polluting than the coal that was previously used. Most of the anthracite, which plants also burn, has been used up. As more soft coal is used, the amount of pollution will increase. According to estimates, fossil fuels will be burned up within fifty years. There are large reserves of uranium. This is still a more lengthy solution to the current burning of coal, gas, and oil.
2. Reliability Nuclear power plants need little fuel, so they are less vulnerable to shortages because of strikes or natural disasters. International relations will have little effect on the supply of fuel to the reactors because uranium is evenly deposited around the globe. One disadvantage of uranium mining is that it leaves the residues from chemical processing of the ore, which leads to radon exposure to the public. These effects do not outweigh the benefits by the fact that mining uranium out of the ground reduces future radon exposures. Coal burning leaves ashes that will increase future radon exposures. The estimates of radon show that it is safer to use nuclear fuel than burn coal. Mining of the fuel required to operate a nuclear plant for one year will avert a few hundred deaths, while the ashes from a coal-burning plant will cause 30 deaths.
3. Safety Safety is both a pro and con, depending on which way you see it. The results of a compromised reactor core can be disastrous, but the precautions that prevent this from happening prevent it well. Nuclear power is one the safest methods of producing energy. There are a number of safety mechanisms that make the chances of reactor accidents very low. A series of barriers separates the radiation and heat of the reactor core from the outside. The reactor core is contained within a 9-inch thick steel pressure vessel. The pressure vessel is surrounded by a thick concrete wall. This is inside a sealed steel containment structure, which itself is inside a steel-reinforced concrete dome four feet thick. The dome is designed to withstand extremes such as earthquakes or a direct hit by a crashing airliner. There are also a large number of sensors that pick up increases in radiation or humidity. An increase in radiation or humidity could mean there is a leak. There are systems that control and stop the chain reaction if necessary. An Emergency Core Cooling System ensures that in the event of an accident there is enough cooling water to cool the reactor.
Also, a nuclear reactor emits virtually no carbon dioxide (CO2), the main greenhouse gas released from human activities (though of course building the power station produces a lot of CO2). They say nuclear power is safe, and that the 1957 Windscale fire in the UK, Three Mile Island in the US in 1979, and even Chernobyl have killed massively fewer people than the oil and coal industries. Beyond that, they say modern reactors are inherently far safer than those built 20 or 30 years ago, reducing a small risk still further. Supporters say uranium prices have remained steady for decades, meaning nuclear energy is far more secure than fossil fuels can ever be.
Cons -
1. Meltdowns If there is a loss of coolant water in a fission reactor, the rods would overheat. The rods that contain the uranium fuel pellets would dissolve, leaving the fuel exposed. The temperature would increase with the lack of a cooling source. When the fuel rods heat to 2800°C, the fuel would melt, and a white-hot molten mass would melt its way through the containment vessels to the ground below it. This is a worst case scenario, as there are many precautions taken to avoid this. Emergency water reservoirs are designed to immediately flood the core in the case of sudden loss of coolant. There are normally multiple sources of water to draw from, as the low pressure injection pumps, containment spray system, and refuelling pumps are all potentially available, and all draw water from different sources.
2. Radiation Radiation doses of about 200 rems cause radiation sickness, but only if this large amount of radiation is received all at once. The average person receives about 200 millirems a year from everyday objects and outer space. This is referred to as background radiation. If all our power came from nuclear plants we would receive an extra 2/10 of a millirem a year. The three major effects of radiation (cancer, radiation sickness and genetic mutation) are nearly untraceable at levels below about 50 rems. In a study of 100,000 survivors of the atomic bombs dropped on Hiroshima and Nagasaki, there have been 400 more cancer deaths than normal, and there is not an above average rate of genetic disease in their children.
3. Waste Disposal The by-products of the fissioning of uranium-235 remains radioactive for thousands of years, requiring safe disposal away from society until they lose their significant radiation values. Many underground sites have been constructed, only to be filled within months. Storage facilities are not sufficient to store the world’s nuclear waste, which limits the amount of nuclear fuel that can be used per year. Transportation of the waste is risky, as many unknown variables may affect the containment vessels. If one of these vessels were compromised, the results may be deadly.
There is also an inevitable link between civil and military atoms, they retort. If we say we need them to stave off climate change, then so can countries like Iran and North Korea - and there is no impermeable barrier between electricity and bombs. They say nuclear energy is economic only under a very restricted analysis - by the time you have factored in the costs of construction, insurance, waste disposal and decommissioning, you need huge subsidies. And, opponents ask, what happens to the waste? The only answer we have come up with so far entails storing the most radioactive waste under guard for millennia, until it has decayed to safe levels. Certainly nuclear power would provide energy to a centralised supply system. But it would do nothing directly to reduce CO2 from transport, unless it made the advent of the hydrogen economy likelier. Also, given the long planning and construction lead times, it would be a good decade or so before we saw any new power stations, even if we decided to go ahead today.
Chernobyl
On April 25th -26th, 1986 the World's worst nuclear power accident occurred at Chernobyl in the former USSR (now Ukraine). The Chernobyl nuclear power plant located 80 miles north of Kiev had 4 reactors and whilst testing reactor number 4 numerous safety procedures were disregarded. At 1:23am the chain reaction in the reactor became out of control creating explosions and a fireball which blew off the reactor's heavy steel and concrete lid. The Chernobyl accident killed more than 30 people immediately, and as a result of the high radiation levels in the surrounding 20-mile radius, 135,00 people had to be evacuated.
One of the causes was a design fault in the reactor - The reactor type used at Chernobyl suffers from instability at low power and thus may experience a rapid , uncontrollable power increase. Although other reactor types have this problem they incorporate design features to stop instability from occurring. The cause of this instability is:
§ Water is a better coolant than steam
§ The water acts as a moderator and neutron absorber (slowing down the reaction) whilst steam does not.
Another was that there was a violation of procedures - While running a test of the reactor numerous safety procedure were violated by the station technicians.
§ Only 6 - 8 control rods were used during the test despite there been a standard operating order stating that a minimum of 30 rods were required to retain control.
§ The reactor's emergency cooling system was disabled.

‘Technical Stuff’!!

21.2.07 08:56

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