Fukushima and Chernobyl – names now synonymous with one thing: nuclear catastrophe. But, as Japan marks the fourth anniversary of the Fukushima disaster on Wednesday, French experts say the two events are far from being on the same scale.
Only two events in history have registered on the highest rung of the scale measuring the severity of nuclear accidents: Chernobyl, on April 26 1986, and Fukushima, on March 11, 2011. It is a fateful similarity that only heightened the wave of fear that spread across the globe following the tragic events in Japan four years ago.
It didn’t help that the company in charge at Fukushima, Tepco, seemed to be completely overwhelmed, barely a day passing without news of new problems at the plant. The international community began to worry that major radioactive contamination could spread throughout the region – even the world.
In the weeks that followed, talk of a “new Chernobyl” filled the pages of the world’s newspapers. But many experts said that it was impossible to immediately measure the extent of the damage to both man and nature.
So now, four years after the event, are comparisons with the monumental environmental and human catastrophe that was Chernobyl still warranted?
Probably not, according to France’s Radioprotection and Nuclear Safety Institute (IRSN), whose experts say the cause of the accident, responsiveness to the disaster and the impact was, in both cases, fundamentally different.
Chernobyl and Fukushima: the causes
When the reactor four of the Soviet Union’s Chernobyl Nuclear Power Plant exploded after a sudden and unexpected power surge, it was largely down to a series of human errors. The containment vessels and building surrounding the reactor literally shattered, a fire sending a plume of highly radioactive material into the open air on a massive scale.
In contrast, the Fukushima accident was triggered by natural causes – an earthquake and resulting tsunami of rare magnitude that damaged the plant's power systems, causing cooling systems to fail at three of its reactors. The situation soon became extremely critical as explosions occurred in the buildings enclosing the reactors. But, unlike in Chernobyl, the containment vessels in Fukushima remained intact. Engineers were able to shut the reactors down.
“The temperature was extremely high, so then the core melted and the radioactive material leaked into the containment vessel and the containment building,” explains Jean-Christophe Gariel, environmental director at the IRSN.
“But it did not reach the open air. It was the building that exploded, not the reactors.”
In 1986, the radioactive material from the Soviet power plant rose into the atmosphere continuously for 12 days, unlike in Fukushima where radioactive contamination occurred mainly from water leaking into the ocean.
As a result, contamination levels in Ukraine were vastly higher – and more dangerous. Extremely harmful chemicals such strontium, plutonium and cesium-137 were released in massive quantities.
“At Chernobyl, three times more cesium-137 was released than at Fukushima, which has a radioactive half-life of around 30 years,” said Gariel. “There was also a massive presence of strontium and plutonium in the area around the plant. At Fukushima, only traces (of these chemicals) have been found.”
In total, the most heavily contaminated areas in Chernobyl were exposed to 20 millions becquerels – a unit used to measure radioactivity – per square metre, compared to 3 million becquerels/m2 in Fukushima.
The area affected by the fallout from both disasters was also significantly different.
“Chernobyl contaminated Europe on a scale of thousands of kilometres, Fukushima contaminated the surrounding area on scale of hundreds of kilometres,” said Gariel.
The whole of continental Europe fell under the shadow of the radioactive cloud produced by Chernobyl. Weather conditions didn’t help: winds pushed the radioactive material to the west and rain brought it to the ground.
In total, an area of 13,000 km2 was affected, to a varying degree, by the fallout from Chernobyl, compared to 600 km2 for Fukushima.
Fukushima also benefited from a slice of good fortune. The catastrophe at Chernobyl happened during the spring, “a time when there is a lot of vegetation … plants, crops were badly contaminated” noted Gariel. “The tragedy at Fukushima happened in winter and, it’s unfortunate to say, but it’s preferable.”
The vegetation at the time in Fukushima was almost non-existent, while a layer of snow protected plants in many places. What was far more devastating was the massive contamination of the sea. Though the radioactive elements were quickly diluted by the vastness of the Pacific, the coastal area around Fukushima and particularly the seabed were heavily irradiated.
“There have been repercussions for marine life in the polluted waters, particularly the species buried in the sediment,” said Gariel. The leaking of radioactive water into the ocean from Fukushima has continued on a regular basis, most recently on February 22, 2015.
Chernobyl authorities fail to react
“The population of Chernobyl was hit head on,” said the IRSN’s Didier Champion in 2012. It took 72 hours before the surrounding population was evacuated from the irradiated areas, long enough for them to be exposed to the full force of the radiation. In Fukushima, there was an immediate evacuation of everyone within a 30km radius of the power plant.
Authorities in Japan were also quick to put food control measures in place, unlike in Chernobyl, where heavily contaminated agricultural products were ingested by the inhabitants.
“Today, in Japan, contamination of most agricultural commodities and livestock is below 10 to 20 becquerels / kilogram [health and safety standards stipulate a maximum of 100 Bq / kg]," said Gariel.
Impact on health
It is still difficult to measure the true scale of the damage done to the health of those exposed to the radiation from Chernobyl, thanks to the Soviets’ wall of silence in the aftermath of the catastrophe. For a long time, all that was known was that 47 people were killed as a direct result of the accident, all of them emergency workers.
Today, we know that there was an explosion in cases of thyroid cancer in the years following the disaster: 8,000 in people under 18, according to the IRSN. Studies have shown that this increase was primarily related to radioactive iodine released during the accident and present, among other things, in milk given to infants.
At Fukushima, studies on the impact on health were launched soon after the disaster, though it is still too soon to tell what the long-term effects on the Japanese population might be. A health survey in February this year, however, reported 86 confirmed cases of thyroid cancer among 297,000 children in the Fukushima Prefecture who were 18 or younger at the time of the accident.
“There were suspected cases in 28 other children,” said Jean-René Jourdain, the deputy director of protection and health at the IRSN.
Health authorities in Fukushima are currently carrying out the second phase of the survey – which is set to continue until April 2017. Ultimately, experts want to "see if it [the figure of 86 cases of thyroid cancer] stabilises or increases”, explained Jourdain.
“Today, as part of this second phase, 75,311 children have been screened. There has been one confirmed case of thyroid cancer and seven suspected cases," added Jourdain, who remains "very cautious" about drawing any conclusions from the study.
Date created : 2015-03-11