It's time to stop being scared of the atom Indeed, "nuclear risk" is in a category all of its own, as was seen all too clearly last year when a major natural disaster, the Tohoku earthquake, which killed tens of thousands of people, was quickly overshadowed in the global collective consciousness by the consequent nuclear incident at the Fukushima plant, which killed no one. A number of countries, most notably Germany changed their national energy policy with regard to the future development of civilian nuclear power. The public reaction to Fukushima and the response compared with other energy-related disasters raises the question: what is it specifically about nuclear power issues that provokes such a strong response? It was back in the Thirties that Otto Frisch and Lise Meitner showed that splitting a heavy uranium nucleus into two lighter elements, such as strontium and xenon, resulted in the release of millions of times more energy per atom than burning coal. Nuclear technology then rapidly expanded as a result of the Manhattan Project, with the construction of superweapons capable of unleashing the explosive power of uncontrolled nuclear fission and, later, fusion. Iconic images of mushroom clouds became fixed in our minds following the devastations of Hiroshima and Nagasaki. And so, for many, civilian nuclear power and images associated with nuclear weapons remain intimately linked. I believe that this emotional link between defence and civilian applications of nuclear technology constrains a rational, scientific analysis of the uses and relative benefits of nuclear power. Certainly, fears of the biological effects of invisible radiation can lead to some bizarre behaviour. The Italian foreign ministry, for example, recommended that its citizens flew out of Tokyo to avoid potential radiation exposure in the first couple of weeks following the Fukushima leak. While the radiation levels in the Japanese capital rose significantly above normal, they remained lower than the typical average background radiation levels in Rome, leading to the bizarre situation of individuals being relocated to places with higher radiation levels than those they were leaving. And a pervasive myth has taken hold that even tiny amounts of radiation are unsafe. In reality, this cannot be so, as humans have evolved in an invisible sea of naturally occurring radioactivity. Much of this arises from radioactive forms of potassium, uranium and thorium; remnants of the Earth's formation more than 4 billion years ago. Human bodies are bubbling with radioactivity, with around 7,000 atoms decaying each second due to radioactivity from potassium-40 and carbon-14. Our understanding of the biological effects of radiation has been developed over more than 80 years, following the first meeting of the First International Congress of Radiology in London in 1925. Radiation-induced effects such as radiation sickness were noted to occur with exposure to specific organs only above a well-defined threshold dose. As to cancer, the probability of a malignant tumour arising is thought to be related to the quantity and type of radiation to which an individual has been exposed. The cohort of Japanese bomb survivors who were exposed in 1945 are the standard baseline for radiation-induced cancer effects in humans, and the majority of the data on the long-term effects of radiation on humans comes from detailed studies of this group. Perhaps surprisingly, of the 87,000 individuals in this cohort more than 30,000 were still alive 55 years after Nagasaki and Hiroshima. This group showed approximately 10,000 deaths from leukaemia and other cancers up to the year 2000, but it has been estimated that only approximately 500 of these individuals died from cancers associated with their radiation exposure to the atom bombs. There have been three major accidents in nuclear power production in more than 14,000 "reactor years" of operational, civilian nuclear power. The reactor core meltdown at Three Mile Island in 1979 made headlines but the melted fuel remained contained within the main reactor vessel, with no measurable radiation health consequences. At Chernobyl a steam explosion blew out the reactor-holding vessel, the reactor core caught fire and a radioactive plume belched into the atmosphere for 10 days, with an estimated 5 per cent of the entire reactor core released. Twenty eight people, mostly firefighters, died within a few weeks of exposure from acute radiation syndrome. According to the World Health Organisation, an additional 19 died between 1987 and 2004 of cancers which might have been radiation-induced. In the 20 years following 1986, no statistically significant health effects on the wider population could be correlated to caesium-137 exposure from the Chernobyl release. But it is what to do with radioactive waste that remains a major and emotive issue in the minds of the public and politicians alike. Although some elements in spent fuel waste can remain radioactive for many thousands of years, the safety issues here seem to be political, rather than technical. Indeed, nature provides excellent examples of nuclear waste storage, with the example of the Oklo natural reactor in Gabon. Geological examination of this area shows evidence of an ancient, naturally occurring nuclear reactor within the uranium-rich mineral deposits which operated approximately two billion years ago. The radioactive "waste material" from the natural reactor at Oklo appears to have migrated less than 10 metres from where it was formed. If this is what happens in nature's random geological disposal site, a carefully chosen, geologically stable deep storage facility for vitrified nuclear fuel waste would seem safe to me. Civilian nuclear power represents approximately one sixth of the world's current electricity production, operating in more than 30 countries. Interestingly, while the civilian nuclear programmes have their ups and downs, fundamental nuclear physics research has never been more vibrant. The danger for future generations is that our residual, Cold War-based fear of radiation means that we face an uncertain future, reliant for our energy needs on coal, imported gas and unproven technologies such as carbon capture and offshore wind farms. Meanwhile Britain's carbon reduction targets remain as unattainable as ever. Our irrational fear of the atom stands in the way of the development of nuclear power and its potentially vital contribution to the long-term energy needs of an ever-increasing and energy-greedy world population. Paddy Regan is director of the MSc course in radiation and environmental protection at the University of Surrey, Guildford