There have been some alarming headlines written about the Fukushima Daiichi nuclear plant in Okuma, Japan, over the last few days. So, what’s going on?
“Radiation levels are soaring,” reported Gizmodo. The Guardian said levels were “at their highest since the plant suffered a triple meltdown almost six years ago.” The Japan Times called it a “blazing radiation reading.”
This all stems from an announcement from Tokyo Electric Power Co, or TEPCO, who runs the plant and are leading the clean-up process. The other day, they revealed they had measured radiation levels at Fukushima's reactor 2 – one of three reactors that suffered a meltdown – at 530 sieverts per hour.
To put that into context, the previous high detected around the reactor since the meltdown in March 2011 – when a tsunami knocked out the reactor’s power – was 73 sieverts per hour. An exposure of 4 sieverts is enough to kill a person.
The meltdown at Fukushima was caused when a 9.0-magnitude earthquake off the north-east coast of Japan triggered a tsunami on March 11, 2011. More than 18,500 people were killed, and the backup power supply at Fukushima was destroyed, causing three of its six reactors to fail. About 160,000 people had to be evacuated as a result, with little prospect of ever returning.
Here's a handy radiation dosage chart, courtesy of XKCD
However, the radiation levels at Fukushima are not rapidly rising, as some reports suggest. Rather, TEPCO found an area with higher levels of radiation than they had seen before. To do this, they used a 10.5-meter-long (34.4-foot-long) telescopic arm, examining an area inside reactor 2 called the “pedestal”.
A camera attached to the arm revealed what looks like a grating that had been melted by exposed fuel from one of the reactors. The images show a square hole measuring 1 meter (3.3 feet) on each side, believed to have originated from melted fuel rods from a pressure vessel above.
If confirmed, this would be the first melted fuel found from the reactor – an important step towards decommissioning the plant itself.
“Nuclear fuel in the Primary Containment Vessel (PCV) was exposed to the air and melted from the impact of [the] March 2011 Great Earthquake,” TEPCO noted in a media handout. “As a result of the accident analysis, it was found that a portion of melted nuclear fuel might have been fallen [sic] inside the pedestal.”
While a higher level of radiation has been found inside the plant, levels around it are continuing to fall. This suggests no radiation is escaping from Fukushima into the surrounding environment.
"There are many people wandering around in Japan with radiation monitors and it would be very easy to see if there was an increase in radiation coming from the plant," Professor Gerry Thomas, a radiation expert from Imperial College London, told IFLScience.
Image in text: How TEPCO took images of the "pedestal. TEPCO
An image of the hole inside the "pedestal". TEPCO