06 August 2008

Moab More Terrifying Than Three Mile Island

Moab, Utah, a village just over the Colorado border from Grand Junction, Colorado is known for its hiking and mountain biking tourism and quaint restaurants, and is vigorously advertising on the radio these days. It is a perfectly safe place to be a tourist, as long as you know that you that the only way to get a wine list in a restaurant is to ask for one, they can't leave them out in Utah.

Fortunately for tourism boosters, Moab has never gotten the fear inspiring press coverage that Three Mile Island or Yucca Mountain have, but the radioactive waste stored near there on the banks of the Colorado River deserves it, despite the fact that this is not the "high level" nuclear waste found at the other two sites. Downstream from Moab are both Las Vegas and Las Angeles (via water projects). A hardly unprecedented flood in the Colorado River could plunge this radioactive waste into this watershed bring the waste close to large human populations, perhaps even into drinking or irrigation water, and exposing fish eaten by local sportsmen.

Coyote Gulch reports on a long belated plan to relocate this waste to a better location by rail (emphasis added).

[The Department of Energy] already has extracted 487,000 pounds of ammonia and 2,100 pounds of uranium from the 130-acre pile, which many people worry might be washed into the Colorado, a source of drinking water for 50 million people.... By rail, there will be one shipment a day, with 17 cars carrying 68 containers for the first three years.


More than 18,000 rail cars of radioactive waste tailings is nothing to sniff at, and an engorged Colorado River could move that waste very fast. We are talking about multiple tons of uranium here mixed into this huge slag pile.

In contrast, Three Mile Island had a containment system that worked, so the worst U.S. nuclear power plant accident ever caused was no harmful contamination outside the plant.

Yucca Mountain likewise would have carefully planned containment and require events orders of magnitude less plausible than a Colorado River flood to pose a serious threat to people or wildlife. Yucca Moutain is also as isolated from immediately local population centers as Moab. With nuclear waste, the danger to populations very close to the radiation source matter much more than large but distant populations (like Salt Lake City with respect to Moab waste, or Las Vegas with respect to Yucca Mountain waste) because radiation intensity declines in proportion to the square of distance from the source.

For example, radiation is 100 times weaker at 10 miles away from the source than at 1 mile from the source, and 10,000 times weaker at 100 miles away from the source, than 1 mile from the source. Likewise, the intensity at 528 feet is 100 times as great as at 1 mile, the intensity at 53 feet is 10000 time as intense as at 1 mile, and the intensity at 5 feet, 4 inches is 1,000,000 times as intense as at 1 mile.

Further, because uranium has such a long half life, it has fairly low intensity radiation even at the source compared to some radioactive materials. One might think of it as a slow steady burn, the nuclear equivalent of a burning peat swamp or underground coal fire, rather than an intense powerful burn like a prairie fire.

Entry of nuclear waste into the fast moving watershed of the Colorado River could bring waste much closer to people than unlikely events like the entry of nuclear waste into much slower moving groundwater aquifers in the middle of nowhere not used widely for human consumption near Yucca Mountain.

The American West should breath easier when the work is done and the threat is reduced.

3 comments:

Anonymous said...

Hi Andrew,

I'd bet that with the small quantities found within the drinking water, combined with the small amount that is absorbed by the human body, combined with the 4.5 billion year half-life of u238, that not a single person will ever be subject to a single alpha particle, which itself is harmless. I'd likely get a more toxic increase in radiation levels by moving from Salt Lake City (my home) to the Denver/Aurora area, a 1000 foot increase in elevation.

Andrew Oh-Willeke said...

If the Colorado River floods before this mess is cleaned up, a lot of people are going to be exposed to health impacting levels of radiation.

Also, I have no doubt that most people are exposed to alpha particles and other radioactivity products in their lives, although Uranium 238 is probably not the most important source of that radiation.

Uranium 235 rather than Uranium 238 is the principal nuclear power plant fuel. This has a very long half-life as well, although it is an order of magnitude shorter than that of Uranium 238. But, nuclear power plants break up Uranium 235 much faster than natural radioactive decay would.

Spent nuclear fuel, in turn, is not dangerous mostly because of the Uranium 235 itself. Instead, it is dangerous as a result of other fission products created during the nuclear reaction "such as cesium-137 and strontium-90, called “fission products,” that account for most of the heat and penetrating radiation in high-level waste. Some uranium atoms also capture neutrons from fissioning uranium atoms nearby to form heavier elements like plutonium. These heavier-than-uranium, or 'transuranic,' elements do not produce nearly the amount of heat or penetrating radiation that fission products do, but they take much longer to decay. Transuranic wastes, also called 'TRU,' therefore account for most of the radioactive hazard remaining in high-level waste after a thousand years. . . . Strontium-90 and cesium-137 have half-lives of about 30 years (that means that half the radioactivity of a given quantity of strontium-90, for example, will decay in 30 years). Plutonium-239 has a half-life of 24,000 years."

Andrew Oh-Willeke said...

According to the U.S. NRC:

"During storage, the spent fuel cools down and also begins to lose most of its radioactivity through radioactive decay, which we've already discussed. In three months, for example, the spent fuel will have lost 50 percent of its radiation; in one year it will have lost about 80 percent; and in 10 years it will have lost 90 percent. Nevertheless, because some radioactivity remains hazardous for thousands of years, the waste must be carefully and permanently isolated from the environment. . . . The radioactive particles in low-level waste emit the same types of radiation that everyone receives from nature. Most low-level waste fades away to natural levels of radioactivity in months or years. Virtually all of it diminishes to natural levels in less than 300 years."

One researcher puts the question like this: How much high level nuclear waste, in the form in which it is stored, "converted into digestible form, would have a good chance of killing a person who eats it — this may be called a "lethal dose." . . .

Shortly after burial 0.01 oz.
After 100 years 0.1 oz.
After 600 years 1 oz.
After 20,000 years 1 lb."