Many people are concerned about possible exposure to radiation as a result of a potential meltdown in the Fukushima reactors.
I’ve only got time for a quick cut here, and will say more in the comments below if asked, but I wanted to point everyone to an excellent blog post by Gia Milinovich which explains some of the scientific issues involved:
From her Twitter feed (@giagia):
I especially like her “Kylie Minogue vs. Mike Tyson” analogy.
A more formal explanation specific to the Fukushima accident is found in this Nature article.
Other isotopes created by nuclear reactors are not as worrisome for the environment. For example, tritium (3H, radioactive hydrogen) has a half-life of 13 years. By convention, we say something stays in the environment for 10 half-lives so that the radioactivity is reduced by 1/210 or less than 1/1000 of its starting amount, so tritium “stays in the environment” for about 130 years; but there is a lot of non-radioactive hydrogen in water that dilutes out the radioactive hydrogen and renders it pretty much harmless. Radioactive nitrogen (16N) is produced in large quantities but decays quickly to non-radioactive oxygen.
131I is both relatively long-lived and rare in the terrestrial environment. This means that it’s not diluted out by other “cold” atoms. There is a lot of iodine in the oceans, so if the prevailing winds and weather take the radioactive iodine into the Pacific Ocean, it will have minimal effects on the environment. If it blows back towards heavily populated land (such as Tokyo), there’s a much larger problem.
What’s worse, 131I concentrates in the thyroid gland. Most other isotopes will distribute themselves evenly through the body, reducing the damage caused by radioactive decay.
The technically minded here might like to read this report.
Even in a much, much larger accident such as Chernobyl, there is a small but measurable increased incidence of thyroid cancer especially in children. If you’re worried, stock up on potassium iodide pills.
- How Iodide Pills Work (livescience.com)
- Radiation exposure: How big is the threat in Japan? – Christian Science Monitor (news.google.com)
- Q&A: Is Japan facing Chernobyl threat? (cnn.com)
- Japanese authorities race to control nuclear crisis (ctv.ca)