It's already been more than five years since three reactors melted down at Japan's Fukushima Daiichi Nuclear Power Plant, but the consequences of the disaster will linger for a while yet. Those monitoring the situation have received some good news, however, with scientists reporting that after suffering the largest ever release of radioactive material into the world's oceans, radiation levels across the Pacific are fast returning to normal.
How to stop the spread of radioactive material from the Fukushima site is a problem that continues to plague the containment effort even now. Tons of groundwater still flows into the reactor basements each day, with some of that then spilling into the sea after mixing with the radioactive material. Signs of contamination have been detected as far away as sites off the US West Coast.
Japan has sought to stem the bleeding by activating an underground ice wall around the facility, which is designed to seal away the nuclear waste. But according to researchers at Australia's Edith Cowan University (ECU), the material continues to seep out into the waters off Japan's east coast.
The ECU scientists partnered with international researchers as part of the Scientific Committee on Oceanic Research to conduct a major review assessing the radioactive caesium levels right across the Pacific, between Japan's coast to North America. Caesium lends itself particularly well to the task of monitoring radiation levels as it is a by-product of nuclear power and is highly soluble in water.
In the immediate aftermath of the nuclear disaster, radiation levels off the coast of Japan were tens of millions of times higher than normal. But after assessing data from 20 studies of radioactivity associated with the Fukushima disaster, the researchers are reporting that these levels are now fast returning to normal.
"Oceanic currents have dispersed the radioactive material across the Pacific Ocean as far away as North America,"says ECU Professor of Environmental Radiochemistry, Pere Masqué. "Radiation levels across the ocean are likely to return to levels associated with background nuclear weapon testing over the next four to five years. As an example, in 2011 about half of fish samples in coastal waters off Fukushima contained unsafe levels of radioactive material, however by 2015 that number had dropped to less than one per cent above the limit. However, the seafloor and harbor near the Fukushima plant are still highly contaminated and monitoring of radioactivity levels and sea life in that area must continue."
Source: Edith Cowan University
Nuclear apologists also pretend that we get a higher exposure from background radiation (when we fly, for example) or x-rays then we get from nuclear accidents.
In fact, there was exactly zero background radioactive cesium or iodine before above-ground nuclear testing and nuclear accidents started.
Wikipedia provides some details on the distribution of cesium-137 due to human activities:
Small amounts of caesium-134 and caesium-137 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Chernobyl disaster.
Caesium-137 is unique in that it is totally anthropogenic. Unlike most other radioisotopes, caesium-137 is not produced from its non-radioactive isotope, but from uranium. It did not occur in nature before nuclear weapons testing began. By observing the characteristic gamma rays emitted by this isotope, it is possible to determine whether the contents of a given sealed container were made before or after the advent of atomic bomb explosions. This procedure has been used by researchers to check the authenticity of certain rare wines, most notably the purported “Jefferson bottles”.
As the EPA notes:
Cesium-133 is the only naturally occurring isotope and is non-radioactive; all other isotopes, including cesium-137, are produced by human activity.
Similarly, iodine-131 is not a naturally occurring isotope. As the Encyclopedia Britannica notes:
The only naturally occurring isotope of iodine is stable iodine-127. An exceptionally useful radioactive isotope is iodine-131…
(Fukushima has spewed much more radioactive cesium and iodine than Chernobyl. The amount of radioactive cesium released by Fukushima was some 20-30 times higher than initially admitted. Japanese experts say that Fukushima is currently releasing up to 93 billion becquerels of radioactive cesium into the ocean each day. And the cesium levels hitting the west coast of North America will keep increasing for several years. Fukushima is still spewing radiation into the environment, and the amount of radioactive fuel at Fukushima dwarfs Chernobyl.)
As such, the concept of “background radiation” is largely a misnomer. Most of the radiation we encounter today – especially the most dangerous types – did not even exist in nature before we started tinkering with nuclear weapons and reactors. In a sense, we are all guinea pigs.