My brother’s birthday is April 26. He turned 21 on Chernobyl day and I must admit that I forgot all about it because of the nuclear disaster. Before that, I had never been concerned about nuclear energy risks. I grew up not too far from a nuclear reactor in the South-West of the Netherlands and its cooling tower was a familiar sight during bike rides in the country. Chernobyl was a rough reminder that there are risks involved with nuclear energy. Admittedly, many of us in the West shrugged off the inherent danger of nuclear power generation pretty quickly. In contrast to our reactors, so we reasoned, Chernobyl had not been designed nor operated safely. The explosions in these early 1986 morning hours were devastating particularly because the reactor did not have a containment vessel. Large quantities of nuclear fuel and core materials were released into the atmosphere.
Fukushima Daiichi is a different story. An earthquake/tsunami mix caused the initial problems, not human errors during a scheduled experiment to test a safety cooling feature as in the case of Chernobyl. The Fukushima plant is a second generation plant with decent containment vessels around its reactors. And, of all operators in the world, the Japanese are perhaps the most diligent and careful. Still. Accidents happen. And big ones at that.
How bad is it? The phones were ringing this morning with reporters asking colleagues and myself about the radiation and explosion dangers. So, here are some facts and thoughts on radiation.
To compare and contrast, we first need to have a unit that measures absorption by our body tissues. For radiation is it the sievert. We all are exposed to radiation, some 0.002-0.003 sieverts (2-3 millisieverts) per year. We quite happily expose ourselves to elevated radiation levels. In a CT scan, for example, the target area receives a dose of 15-30 millisieverts. X-rays are very much lower than that. Overexposure is dangerous as it has been shown to increase the risk of cancer. It is still difficult to give accurate risk numbers, but exposure to 0.1 sieverts a year (50 times the base radiation levels we all experience) is already considered a cancer risk. Indeed there is some evidence (particularly for children) that an accumulated dose of 0.09 sieverts from two or three CT scans leads to an increased risk of cancer. My colleagues in the school of medicine tell me that if 100 people were exposed to a total of 1 sievert, five of them would develop a fatal cancer over a number of years. If two people were exposed to a dose of 5 sieverts, one of them would probably succumb within a month. It still all sounds a bit vague, but that’s about the level of our understanding right now. Apart from cancer, there is a risk of compromising the immune system as radiation can damage red and white blood cells.
So, how much exposure was there in Chernobyl, and how much is there now in Fukushima? Estimated numbers for Chernobyl range from 300 sieverts per hour in the vicinity of the reaction core, to 0.03-0.05 sievert per hour in the control room and 0.1 sievert per hour in a nearby unit. Clearly, anyone near the reactor at that time was in grave danger. The reactor crew chief, Alixander Akimov, died from radiation exposure within weeks. In the aftermath, nearly 240 people suffered from acute radiation sickness and 31 died within three months. During Chernobyl, a total exposure of 0.35 sieverts (350 millisieverts) was used as the relocation threshold. More than 100,000 people were indeed evacuated.
In the first few months after the accident in Chernobyl there was anxiety about contamination of river and reservoir waters. Levels were too high, but after a few months they decreased to acceptable levels. Another concern was the contamination of fish. Groundwater was not badly affected. The reaction to the outfall in Europe was strange, to say the least. Some foods were banned. I remember being advised not to eat any Scottish beef. In France, however, officials decreed that all was safe.
The total amount of radioactive material released by Chernobyl was a few hundred times more, as estimated, than Hiroshima. Fallout was detected over most of Europe. It is believed that half of the particles landed outside the Ukraine, Belarus and Russia and that over one million people were affected by radiation. It is however very difficult to get any numbers of radiation exposure, and it is still unclear how many people died as a result of radiation exposure in the 25 years since Chernobyl. It takes some 10 years or more for cancer to be exposed and the World Health Organization report written about it was within that latency period. UNSCEAR, the United States Scientific Committee of the Effects of Atomic Radiation, conducted over 20 years of research on the effects of Chernobyl. Initially, UNSCEAR feared someo 4000 additional cancer cases would be due to the accident, but later that number was shown to be too high. Thyroid cancer cases did go up, says UNSCEAR, particularly in children and adolescents explosed at the time of the accident. Thankfully, thyroid cancer is generally treatable. UNSCEAR further stated that it could find no further evidence of increases in overall cancer incidence or mortality rates. However, other organizations and individual researchers, report much more devastating impacts of the radiation, with one (New York Academy of Sciences report in 2010) apparently claiming 985,000 deaths as a result of the radioactivity released. I say apparently, because I have not read this report myself. Clearly, there is still a lot of debate and controversy surrounding Chernobyl, caused also by lack of reliable accounting in the former USSR.
What about Fukushima? Yesterday, Japan’s Chief Cabinet Secretary Yukio Edano said that they recorded as much as 0.4 sieverts an hour near the plant. 70,000 people have been evacuated from the area directly surrounding the plant. 140,000 people in areas further removed have been asked to stay indoors and seal their homes as best they can. In Tokyo, slightly higher than normal radiation levels have been detected, but nothing to worry about, thus far. Excellent current information about radiation levels and other updates can be found at MIT’s Nuclear Information Hub: http://mitnse.com/.
Fukushima is still in a very dangerous stage. Keep your fingers crossed and your eyes on the sieverts.