Thursday, July 8, 2010

Isn't Spent Nuclear Fuel a Problem?

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?

No comments:

Post a Comment