Keeping Score on Nuclear Accidents
Now that Japan has raised its assessment of the Fukushima accident to a 7 on the International Atomic Energy Agency’s scale, equal to the 1986 accident at Chernobyl, it may be time to review past accidents. Thomas Cochran, a physicist at the Natural Resources Defense Council, just did that in preparing to testify on Tuesday afternoon before the Senate Environment and Public Works Committee.
Some of the incidents that he lists are technically not meltdowns but rather “core damage accidents.” That term is used when an intact core holds in nearly all of the radioactive materials that are created by a reactor as it splits atoms of uranium and plutonium, leaving behind fragment atoms of materials like cesium, strontium and iodine, which seek to return to stability by giving off radiation. If the core melts, as it did at Fukushima, or explodes, as it did at Chernobyl, that radioactive material is released.
The seven-level scale for the accidents’ seriousness runs from “anomaly,” something that would probably not be mentioned in a newspaper, to “incident,” which might be, to an event with major off-site consequences for health and the environment, like Chernobyl or Fukushima.