What reading that article told me is that, first of all, it is unfortunate that Science magazine, a highly respected journal, should fall for such sensationalism. Secondly, the article told me that, even in the "hot zone", the radiation is not outside of the normal range of background radiation.
From the linked article:
Radiation in this zone is 0.4 microsieverts per hour, or about 3.5 millisieverts per year. That is a fraction of the radiation found throughout much of Fukushima Prefecture, which surrounds the nuclear power plant. But it is still 10 times background levels and even above the 1-millisievert-per-year limit for ordinary citizens set by Japanese law. The health effects of such low doses are not clear and are passionately debated. But it is known that children are more susceptible to radiation than adults, and few parents want to take chances with a child's health. Besides, The law should be observed, Yamauchi says. Kyo Kageura, an information scientist at the University of Tokyo, says there should be a public discussion of the issue, based on a scrupulous presentation of the data, including to what extent the 1-millisievert limit can be achieved.
The 1 millisievert limit set by the Japanese government is highly unrealistic. The average background exposure worldwide is 3 millisieverts, and ranges from "0 to tens" according to this Wiki article. Actually, I have my doubts about the low end of the range; I don't know that any place exists where background radiation is zero.
For clarity, the limits are all annual limits.
You would want to check the background levels of radiation before humans invented nuclear energy and bombs. Pre-nuclear metals from WWII like German made ships command a high salvage price since it is ‘clean’ from background readings.
Like I said, nuclear radiation is new to the human race as some of the radionuclides (byproducts) never existed before in nature.
If you think radiation just disappears, you are fooling yourself, sometimes it takes hundreds of thousands of years to breakdown.