Radioactive iodine in food is of immediate concern, but it has a relatively short half-life and will naturally decay over a short time frame.

食品中的放射性碘直接引起人们的关注，但是它的半衰期相对较短并将在短时间内自然衰变。

youdao

Most famously, uranium-238 decays into lead-206 with a half life of 4.5 billion years, though radioactive rubidium and samarium are also useful for dating things billions of years old.

最为有名的就是铀- 238衰变为铅- 206的半衰期为45亿年，当然放射性铷和钐也同样对测算几十亿年前的物体的年龄很有用。

youdao

The city's challenge, chiefly, is to dispose of cesium-137, a radioactive isotope with a half-life of 30 years.

这座城市面临的最大问题就是处理铯—137，这是一种半衰期为30年的放射性同位素。

youdao

Cesium-137 has a radioactive half-life of about 30 years, and traces of the isotope still persist from above-ground nuclear bomb tests in the 1950s and '60s.

CNN: Fukushima tuna study finds minuscule health risks

Because of the short half life of radioactive iodine (8 days), in a month or so the water should be fine again.

FORBES: Japan Warns On Radioactive Water

Once read they will self-destruct in your brain faster than the half-life of radioactive cobalt.

CNN: ASIANOW - TIME Asia | Asia Buzz: Geomancy for the Millennium