worst case scenario for radiation

Record high levels of radiation have now been found near the Fukushima 1, nuclear facility following explosions at reactors 1, 2, 3 and 4. Radiation 9 times the background levels have been found near Tokyo.

A critical factor now is wind direction. The simulation above shows the potential radiation plume based on weather forecast data and a worst case scenario for radiation.

Timeline of recent events at Fukushima 1 (Daiichi):

Sunday, afternoon - Explosion at unit 1 confirmed by Japanese officials.

Monday, late morning - Explosion at unit 3 confirmed by Japanese officials.

Tuesday, morning - Explosion at unit 2.  The explosion is feared to have ruptured a part of the reactor containment vessel (the concrete containment) called the wetwell (also known as the torus or suppression pool). Fuel melt is still ongoing, with latest information putting water level at around minus 2 meters, meaning half of the fuel rods are exposed.

Tuesday, morning - Fire starts at unit 4, followed later by an explosion. Reactor 4 was shut down cold with no fuel loaded at the time of the quake, meaning that the spent fuel pool is the likely source.  

These were all thought to be hydrogen explosions (though it is uncertain).  They are not nuclear explosions, as with a nuclear bomb.  The risk to the wider public is caused by radiation from the reactor core or stored nuclear materials.  Workers have reportedly been injured in some of the blasts.

Health and safety situation


• Extremely high levels of radiation were measured around Daiichi on Tuesday morning. Near Unit 4, 100 - 400 mSv/h are reported, and levels of 30 mSv/h between Units 2 and 3. Levels were explicitly confirmed to be measured in milli-Sievert, not micro, by government secretary Edano, which means an immediate threat to health and a hundred times more than any measured so far.

• People within 20-30 kilometer radius of the plant are being told by the government to stay inside, turn off ventilation and dust off their clothes and shoes, as well as take a good shower if they come in from outside.

• Radiation levels nine times background were measured as far as Kanagawa, which is 250 km South-Southwest and very near to Tokyo. In Utsunomiya, 140 km Southwest of the site, levels were 33 times above normal. In Sendai, 100 km North, officials told everyone to avoid rain as it would carry radioactive contamination. Forecasted wind direction is South East to East, meaning inland and potentially toward Tokyo.


• According to Japanese government secretary Edano, Unit 4 is believed to be the source of the high radiation levels, which makes it even more alarming - spent fuel has much more long-lived isotopes than a hot reactor core, meaning more potential for long-term contamination.

What's next?

It is very difficult to predict what happens next. The situation at Units 2 and 4 is not under control and potential for large radioactive releases exists. The high radiation and damage at the facility makes work their extremely difficult. Our thoughts are with those suffering through the aftermath of earthquake and tsunami and this unfolding nuclear crisis.


We will continue to monitor the situation and post updates on this page and our Twitter account.

The forecast of wind direction from the state meteorological service of Austria - ©zamg