25 years ago in the sleepy Soviet controlled village of Pripyat, Ukraine, an event occurred that branded a word onto the world's collective conscience. In the early hours of the morning, the plant was rocked by an explosion, resulting in nuclear waste products being strewn over a wide area. Since then, Chernobyl has become a word that conjures up fear, loathing and invokes a wide range of impassioned reactions. Discussion on the issue is overrun with fearful rhetoric, and the very name tends to galvanise people. Any time the subject of nuclear power comes up, opponents tend to cite Chernobyl as some kind of proof that it is inherently flawed and more dangerous than other forms of power generation. Whispers about detrimental health and environmental effects terrify people to the point that rational discussion about the events and aftermath of Chernobyl and indeed nuclear power are difficult and emotive. This was entirely understandable; an event like Chernobyl had never occurred before so assuming the worst was understandable - there was simply a shortage of information on how things would transpire. But now, a quarter of a century later, with the benefit of hindsight and over two decades of intense scientific research, it is time to reexamine the disaster and its consequences in light of what we now know.
The first step is to understand what happened at Chernobyl on that infamous day - the explosion happened when engineers at the plant were running an experiment to test and improve the reactor cooling rates. Due to a combination of bad engineering and poor design, a power spike occurred. This raised the steam temperature which resulted in an initial explosion. Seconds later, there was a second explosion. This second explosion was the result of a criticality accident, when nuclear fuels and products mix outside of the designed areas and undergo nuclear fission. This explosion effectively stopped the nuclear chain reaction, but expelled a high volume of nuclear byproducts. Contrary to safety regulations, the roof had been made with bitumen, a flammable material. This began to burn, along with the graphite control rod. The resulting fire exposed radioactive material beyond the confines of the plant. The fire brigade arrived to put out the fire - amazingly, they were not given any protective gear, nor indeed were any precautions taken. They battled the flames for hours and successfully subdued most of them. Sadly for their bravery, many of them died soon after from radiation sickness. It was only days later that the town of Pripyat was evacuated, and that didn't occur until a detection site at a nuclear plant in Sweden registered above normal background levels, forcing the Soviets to admit the situation. The transformation of Pipyat into an exclusion zone and the shocking culpability of the soviet authorities are well known, but before the health effects can be discussed, It is helpful to have a clear picture of what radiation is, and why over-exposure is damaging.
Radiation refers to any energetic particle or waves which travel through a medium. Generally 'radiation' refers to what is called ionizing radiation - particles or waves with enough energy to knock electrons out of atoms / molecules. Ionizing forms include X-ray, Gamma rays, and Alpha articles. Radiation can also refer to non-ionizing forms of radiation, like radio waves, microwaves and visible light. Radiation is all around us all the time and has been since the dawn of humanity. There are background levels of radiation everywhere, and doses we can easily endure with no ill effect but over-exposure to ionizing forms of radiation can have detrimental consequences as it can remove electrons from atoms / molecules. When an atom / molecule is stripped of an electron, they become electrically unpaired and as a result highly chemically reactive. These particles are known as free radicals, which tend to react with whatever organic material happens to be around and can cause cell damage. While the human body does have mechanisms for dealing with this damage, damaged cells can sometimes evade these protection mechanisms and proliferate with the end result being carcinogenesis or the formation of cancer. Single large doses can accelerate the normal physiologic process of apoptosis (programmed cell death), resulting in tissue which is unable to function correctly. This condition is called acute radiation syndrome (ARS) and the severity is dependant on dose with effects ranging from nausea to death. In radiobiology, absorbed dose is a predictor of health effect - the e gray (Gy) measures the amount of energy absorbed by an object per kilogram of mass. However grays on their own don't fully tell us what the biological effects are, as different types of radiation have different levels of impact. Alpha radiation has roughly 20 times the effect of gamma radiation on human tissue for example. Different tissue also various weighing factors. These can be combined in a unit that allows quantification of the biological impact of radiation exposure. This unit is called the sievert (Sv). It is s a large unit, so often doses are given in millisieverts (mSv) which is one thousandth of a sievert and microsievert (uSv) which is one millionth of a sievert. In Ireland, the background radiation dose will be about 2-3mSv a year. In parts of Europe and Asia the background rate can be as high as 50mSv per year. A single dose of 1000 mSv or 1 Sv would be enough to induce temporary nausea , vomiting and even bleeding. A single dose of 10 Sv would almost certainly kill rapidly. Severity of damage is not just dependent on the dose and type of radiation, but also the rate this is delivered at. A patient undergoing radiotherapy for cancer gets doses in the order of 20,000 mSv in the healthy tissue surrounding the tumour but as this is spaced out over several days it gives exposed tissue time to repair and replace.
Chernobyl was without question the worst nuclear power accident of all time. Exposure at the core immediately after the events would result in about 30 Sv per hour, certainly a fatal dose. The fire fighters and rescue workers that battled the blaze directly were directly exposed to massive doses and many consequently died. Apart from the health effects some radioactive fuel was expelled into the atmosphere, allowing it spread radioactive iodine 131. Iodine 131 doesn't live for long (a half life of 8 days) but it can be absorbed by the thyroid and can cause thyroid cancer. But how many health effects can be attributed to the disaster ? Fittingly, the latest report from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) dealing specifically with Chernobyl has recently been published. The report makes for harrowing reading in so much as it makes clear much of disaster was avoidable. It also contains information on the cost to human health from the disaster. 134 Plant workers and clean up workers were exposed to dangerously high levels of radiation with minimal protection and suffered ARS. Of these 28 died. There were 15 fatal cases of thyroid cancer in children, which could have been avoided with iodine tablets. Those who imbued radioiodine immediately after the disaster are at elevated risk of thyroid cancer, which is quite treatable with a 92% 30 year survival rate. No increase has been observed in solid cancers or birth defects. The Chernobyl forum concludes the greatest threat to survivors is the risk to mental health from exaggerated fears about radiation, noting ".. designation of the affected population as “victims” rather than “survivors” has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption of game from areas still designated as highly contaminated, overuse of alcohol...and unprotected promiscuous sexual activity". These are conclusions people often find surprising, expecting the health toll of Chernobyl to be much greater. That this toll is considerably less than people might expect does not take away from the tragedy or make the soviet response any less dreadful; Chernobyl cost the lives of at least 43 people and some of those exposed in 1986 may yet die early. That the authorities attempted to conceal the accident and didn't evacuate immediately or issue iodine tablets is no less dire. That the disaster occurred at all is damnable. Despite the enormity of the accident, all of those 43 lives could have been saved if proper precautions had been followed.
Some take issue with these figures; the Russian non-peer reviewed publication Chernobyl: Consequences of the Catastrophe for People and the Environment claims 985,000 died as a result of the accident. Similarly, Greenpeace have claimed a figure of over 200,000 deaths. However, a subsequent investigation by the Oxford journal Radiation Protection Dosimetry exposed this as an utter shambles. George Monbiot of the Guardian explains "A devastating review in the journal Radiation Protection Dosimetry points out that the book achieves this figure by the remarkable method of assuming that all increased deaths from a wide range of diseases – including many which have no known association with radiation – were caused by the Chernobyl accident. There is no basis for this assumption, not least because screening in many countries improved dramatically after the disaster and, since 1986, there have been massive changes in the former eastern bloc. The study makes no attempt to correlate exposure to radiation with the incidence of disease." By contrast, the UNSCEAR reports are meticiously researched and conducted by several bodies, including the World Health Organisation. The important thing to take home is the dichotomy between what people expect and what actually is. This cognitive dissonance between the reality and the collective consciousness is jarring, but understandable. The spectre of the Cold War left the impression of imminent nuclear destruction on the psyche of the world. The events of Chernobyl occurred during this fraught period, and naturally public understanding conflated an explosion at a nuclear plant with a nuclear explosion. This is understandable but unfortunate, as the mechanism behind nuclear weapons is entirely different to nuclear power and one cannot simply turn a nuclear plant into an atomic bomb. This is turn must make us reevaluate our attitudes to Chernobyl; while is was undoubtedly a tragedy, it must be looked at in context if we are to have informed debate on nuclear power.
These questions are even more relevant now, with the problems at Fukushima. As of yet the accident at Fukushima has thankfully not claimed any lives but that has not stopped a predictable knee-jerk reaction against nuclear power, as Chernobyl did before; Several nations have questioned the viability of nuclear power. But dismissing nuclear power out of hand is not a good course of action. Nuclear energy is complicated and has some disadvantages, but it is clean, efficient and doesn't burn fossil fuels. With a rising world population and depleting oil reserves, dismissing nuclear energy based on a magnified fear is foolish and premature. This does not mean ignoring renewable energy, but recognising that renewable technologies suffer from the flaw they do not produce constant output and we cannot store electricity for long periods. To be pragmatic we need constant energy producers like nuclear in tandem with research into improving renewables. We also need to maintain perspective - the worst nuclear disaster in history at Chernobyl claimed 43 lives. By contrast when the Vajont hydroelectric dam failed in 1963, over 2000 people perished. Over ten times worse was the failure in 1975 of Banquio dam, where over 26,000 people died and vast tracks of land destroyed. Another 145,000 died from the resulting famines and epidemics. These are not stated to rubbish hydroelectric power, merely to give perspective and highlight the fact all energy technologies have some degree of risk. To demonise nuclear power is remiss, given the numbers indicate that accidents involving renewable and fossil fuel plants claim many more lives. Radioactivity is invisible and threats we cannot see are frightening but a misplaced sense of radiophobia should not be the underlying motivation in deciding how to best power our world.
|The Iconic Pripyat Ferris Wheel. At least there's no queues.....|