Making the invisible visible: measuring radiation in Japan | Asia| An in-depth look at news from across the continent | DW | 08.03.2012
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Making the invisible visible: measuring radiation in Japan

Many Japanese are worried about so-called hot spots, radioactive patches located in otherwise uncontaminated areas. Distrustful of official government information, they have now started collecting data themselves.

Public distrust toward nuclear power plant operators and government institutions in Japan has increased considerably since the nuclear meltdown in Fukushima. Authorities claim there is no danger for the population outside the 30-kilometer evacuation zone surrounding the disaster area.

But many Japanese people feel they cannot trust government recommendations. Too fresh in their memories is the case of Iitate, a village located 45 kilometers (28 miles) northwest of the Daiichi plant, where high levels of radioactivity were detected. The village's 6,000 residents weren't evacuated until around two months after the meltdown.

Prefectural government's employees monitor amount of radiation on the ground of a day-care center in Iitate

High levels of cesium were detected in Iitate

Radiation emanating from the damaged power plant has not spread evenly throughout the country. Measurements have shown that areas with extremely high levels of radioactivity can be tucked away near areas which do not have elevated values. That means merely crossing the street could be enough to put one's life in danger.

The invisible killer

The fact that radiation is invisible is a greater cause of worry for the Japanese people, who do not feel they can trust the government and are not sure how to protect themselves.

In order to promote awareness and provide information to the people, a group of engineers, researchers, computer scientists and environmental activists from Japan and the US founded an initiative. What had originally started off as a gathering of a group of friends and acquaintances turned out to become something of a crisis committee.

Screenshot Safecast

Safecast provides the information collected on an interactive map

Household Geiger counters

A Hawaiian company which manufactures Geiger counters joined the group along with the operator of a website in Portland, which keeps an interactive map showing radiation data. This was the beginning of the "Safecast" - a citizen's project for which people collect data on radiation using Geiger counters and send in their readings.

One obstacle the initiators initially had to overcome was making sure the project's participants had the right Geiger counters which delivered consistent results. In April 2011 they started developing a relatively simple counter for “household use.“ The counter is called bGeigie and it measures radiation using an industrial-power but highly sensitive standard sensor. In order to avoid mistakes and also to verify the data, Safecast activists always gather data using two separate counters.

Radiation hot spots

In Tokyo alone, which is located around 260 kilometers from Fukushima, activists found around 20 radiation hot spots up to October 2011. The concentration of radioactive particles there was so high, that it could have posed a health risk. But so far, the authorities have not carried out a systematic probe of soil samples in these hot spots. Instead, the government has commissioned reports on air samples usually taken around 10 meters above the ground - an altitude at which human beings are not generally found.

A Greenpeace team member holds a Geiger counter displaying radiation levels at Iitate village

Not all Geiger counters are good enough for the activists

The tests commissioned are also usually done in one part of a town or a city, but the results are used to conclude radiation values for the whole of the city or town. Safecast measurements, on the contrary, are taken at 1.5 meters above the ground; samples taken here give a better idea of the air humans breathe.

Strongly polluted hot spots are contaminated with cesium-137, which has a half-life period of around 30 years. But other radioactive material, like cesium-134, which starts to decay after only two years, will still be detected in years to come.

These particles emit beta radiation. That is low level radiation which normally cannot penetrate paper or cloth. It is toxic when inhaled or ingested. Although Safecast activists have also searched for more dangerous isotopes such as plutonium, strontium and iridium, no traces have yet been found. Other organizations were, however, able to find traces of these materials right after the nuclear meltdown in Fukushima in March, 2011.

Author: Fabian Schmidt / sb
Editor: Arun Chowdhury

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