Tuesday, July 13, 2010
Saturday, July 10, 2010
Even without Inherently Safe Nuclear Reactors, the nuclear industry has the best track record of all power producing industries as far as safety is concerned. There has been only one severe accident in the history of nuclear power usage that caused loss of life. This accident occurred at Chernobyl in the Ukraine, and resulted in the loss of 56 lives.
While the accident at Chernobyl was horrible and something we want to avoid in the future, it pales in comparison to the loss of life from other energy sources. Chernobyl was caused by what could be described as an unsafe experiment in reactor physics done by ill trained personal. The Chernobyl reactor was also an unsafe design that does not lose moderation when the coolant is lost. The Chernobyl reactor used graphite as a moderator, while western designs typically use the coolant itself as a moderator. When a design that uses the coolant as a moderator experience loss of coolant, the nuclear reaction slows and becomes less intense. The opposite happened in the Chernobyl reactor, and without the containment that is standard in Western designs there was release of radiation into the environment. We can definitely do better, and avoid this sort of accident in the future.
In the United States and the European Block, we have never had a commercial nuclear accident that caused the loss of life. There have been studies and analysis that considered the replacement of the Barsebäck nuclear reactor in Sweden with coal power. For the same generating capacity the study concluded with a high probability that around 200 lives per year would be lost by replacing one nuclear reactor with a coal fired plant producing the same energy output.
Here is a chart detailing deaths per terawatt hour:
One nuclear power plant typically produces 1 gigawatt continually. Over an entire year if run at 100% capacity it generates 8760 gigawatt hours of electricity, this can also be expressed as 8.76 terawatt hours.
The mean average number of deaths per terawatt hour for coal is 25 deaths for the European Union. The mean average number of deaths per terawatt hour of generating capacity for nuclear is 0.02 deaths (An ExternE report, a research project done in the European Union to determine the external costs for energy generated was the source for the numbers used in the following calculation.)
8.76 terawatt hours * 25 deaths per terawatt hours = 219 deaths per year from coal.
8.76 terawatt hours * 0.04 deaths per terawatt hours = 0.3504 deaths per year from nuclear.
The study makes a further statement that the risk of death from a nuclear accident was very unlikely and the risk of death from coal was very high, essentially 100%.
The chart above came from the following report available on the internet:
Additional information about the ExternE project in general is available at:
Nuclear power is the safest power producing technology we currently possess. To call nuclear power unsafe just does not make sense given the numbers. Additionally with basic fundamental research, we will only further improve the situation.
Thursday, July 8, 2010
We have been told that spent nuclear fuel is a huge problem. It is something that is currently a difficulty, but with investments in technologies that we have known about for 40 years the problem becomes much more manageable. Even in its current state, nuclear waste is significantly better then our other energy choices. The coal plants that currently produce around 50% of our power have a much nastier waste problem. Based of statistics from 2005, there is approximately 336 gigawatts of generating capacity from coal in the United States. In total these plants burn 1.05 billion short tons of coal, and generate 120 million short tons of toxic waste. To put things in perspective that is roughly equivalent to having something the size of a 1990 Honda Civic for every family in America. (A 1990 Honda Civic weighs 1 metric ton, 120 million short tons is approximately 108,862,000 metric tons and as of the 2000 census we have 105,480,101 households in the United States.)
The amount of arsenic alone in this amount of coal is enough to kill every man woman and child on the planet ten times over. In the 1.05 billion tons of coal there is 7884 tons of arsenic, 109 tons of mercury, 1167 tons of beryllium, 8810 tons of chromium, 750 tons of cadmium, and 2587 tons of selenium, and 9339 tons of nickel. Coal combustion waste is the second largest waste stream in the United States.
If we average out the 120 million tons of coal waste by gigawatt of electricity generated for a year, we get an average of 357,000 short tons (323,994 metric tons) of toxic waste per gigawatt / year. A single large nuclear power plant generates only 35 metric tons of spent nuclear fuel per year, while producing 1 gigawatt over that year. If we could replace all of our coal generating capacity with nuclear reactors tomorrow, we would produce approximately 11,760 metric tons of spent nuclear fuel per year. This is still a large amount of waste, but it is about 1 / 10,000th the amount of waste.
Most of the spent fuel is not waste, but in the United States we do not reprocess our fuel. Around 1 ton of the spent fuel consists of fission products, and 0.3 tons is plutonium. The remainder of the fuel is primarily a mix of U-235 and U-238. With an efficient reprocessing technology we can reduce the waste portion of spent nuclear fuel significantly. If we remove the Uranium metal from our spent nuclear fuel, we are left with only 437 metric tons of waste to match the generating capacity of coal. The plutonium is the longest lived component of the waste portion, and the 101 metric tons produced of it can be burnt in fast reactors as fuel. By reprocessing our fuel and burning it in fast reactors we are left with 437 metric tons of fission products. Many of these fission products are useful industrially, but even if we consider it all as waste we have 4 / 100,000th the quantity of the coal waste. An efficient and responsible nuclear industry would produce 437 honda civic's worth of nuclear waste per year. Nuclear waste processed in this manner would decay in about 300-500 years to the activity level of Uranium ore.
Why are we burning coal when we could do so much better?