By, Wade Allison
Emeritus Professor of Physics at the University of Oxford
An educational article written for the Nuclear Literacy Project, September 2012
Where I am coming from
I am not an “activist”, a “nuke” in a white coat hiding in a government bunker, or even an “expert”. I am a teacher – I have been researching and teaching physics at the University of Oxford for over 40 years (medical physics, radiation physics, nuclear physics and most of the relevant stuff). I do not like being called an expert because I want to explain and show why. I do not want to dictate what people should think and decide, but I do want to ensure that they are informed. I am a grandfather who knows about nuclear and is driven by the hope that his grandchildren will enjoy the benefits of living with nuclear technology without which their future looks grim.
The background information that you need to understand nuclear power may be unfamiliar but the basic ideas are not complicated and they describe a world that is safe. There are lots more explanations in the book “Radiation and Reason” and in the articles and links on the website: http://www.radiationandreason.com
The story of the underlying science
We should start with the science. Everything is made of atoms and these are all about the same size as one another, about ten thousand times smaller than the smallest thing you can see with your eye. These atoms stick together in various ways – chemistry describes what happens when they are re-arranged, for example in burning and the use of food as fuel for our bodies. But at the centre of every atom is a nucleus, an amazing hundred thousand times smaller than the atom. It is heavy and electrically highly charged but it does absolutely NOTHING. In fact, on Earth, only 1 nucleus in a million has changed in any way since the Earth was formed some 6,000 million years ago – this rare nuclear change is called radioactive decay. The only other kind of activity occurs at the centre of the Sun where the temperature is millions of degrees, and once every few thousand million years each nucleus hits another and reacts to form helium — this is the source of the Sun’s energy. Otherwise- every nucleus remains completely isolated, pushed away from its neighbours for ever by the intense repulsive force coming from its electric charge and exceptionally small size.
The Sun shows that nuclear changes are very energetic though very rare. In fact the energy per kilogram of nuclear fuel in a reactor is about a million times greater than for chemical fuel, such as coal or oil. Incidentally this means that, for the same electrical energy from a power station, the amount of nuclear fuel needed (and its waste) is about a million times less than the equivalent fossil fuel and its waste (the dreaded carbon dioxide).
The inside of the Earth is hot and the heat powers volcanoes and earthquakes (and thence tsunamis) like the recent one in Japan. Lord Kelvin showed long ago that the Earth would cool down naturally in a few million years. So what has kept it hot for a thousand times longer? The answer is the natural radioactivity within the Earth that has been there since its formation 6000 million years ago. So this “natural” radioactivity caused the tsunami in north east Japan that killed over 18,000 people. But what about the radioactivity released from the Fukushima nuclear reactors as a result. Where did that come from and how many people has it killed already, and how many in the future?
Controlling nuclear energy
There is just one way to overcome the electrically imposed isolation of all nuclei, and that is with something that is not electrically charged at all. A neutron is the only candidate – a proton is the simple nucleus of a hydrogen atom and the neutron is its uncharged twin. But free neutrons do not exist in nature — they are quickly absorbed or otherwise decay in a few minutes. As a result they exist only inside a nuclear reactor that is “on” at the time, or inside a nuclear weapon at the moment of explosion. For example, as soon as the earthquake in Japan was sensed, all nuclear reactors were turned “off” by absorbing the neutrons. By the time that the tsunami struck there was only radioactive decay in the reactors. This generated a lot of heat and that in turn caused much damage in the absence of sufficient cooling water to keep the temperature and pressure down.
The damage that then occurred was chemical not nuclear. At the high temperature the nuclear fuel containers made of the metal zirconium reacted with water releasing hydrogen, in the same way that sodium does at room temperature. Because of the excessive pressure the hydrogen had to be released from the reactor, and this then exploded in the air when it got outside – that was no worse than the fires that destroyed the oil refinery struck by the tsunami. “Well, it was worse,” I hear you say, “because of the radioactivity released into the environment at the same time as the hydrogen. I know because I saw it on TV!” But that radioactivity has caused no deaths, nor will it cause any in the years to come. All this was known at the time, but the media do not like good news to get in the way of a story of a real DISASTER with explosions on video, and anyway the authorities who should have known better were unprepared and mesmerised. Seen as nuclear explosions they sold news and frightened many, causing nuclear power production to be closed or run down around the world. So the man-made radioactivity at Fukushima killed nobody, but the natural radioactivity in the Earth powered the tsunami that killed many thousands.
Natural radiation protection
But that is hardly the end of the story – as scientists we want to understand WHY such a powerful agent as nuclear radiation does not kill people. Look! the forces that hold our DNA together are pathetic compared with nuclear energy – the DNA is easily smashed. So why does it not cause major loss of life? In fact DNA is also fairly easily broken by rogue chemicals and simple chance collisions between molecules of the type that happen at the temperature of our bodies. Looks pretty bad, doesn’t it?
But we missed something – biology! The business, in fact the only business, of biology is to conserve life. Evolution has spent hundreds of millions of years perfecting ways to protect life, that is DNA, from attack, whether chemical, radiation or random. In modern biology many of the design features and active ways that provide such protection have been discovered and every year more are found. Here are a few simple ones:
- ‣ each organism consists of many cells, each with their own DNA copy for safe keeping;
- ‣ cells are replaced in the cell cycle but many damaged cells fail to reproduce;
- ‣ damaged cells are identified and destroyed by other cells, the immune system;
- ‣ DNA has a ladder structure, a double strand, to help unique repairs;
- ‣ in each cell enzymes are available to repair most of the damage to DNA within hours of an attack;
- ‣ all individuals are replaced in the cycle of birth, life and death.
Such natural radiation protection through passive design and active response is provided to all life –plants as well as animals – and works in humans without involving consciousness. So unless a radiation dose is very high indeed we should expect life to survive it, even if TV channels would prefer something more exciting. But where is the evidence that this actually works for humans exposed to radiation?
What do we know?
We meet radiation in three scenarios: in the natural environment, in health care and, possibly, as a result of a nuclear accident. The same kinds of radiation are involved in every case and there is essentially no difference except for variations in the size of the dose and the period over which it is received. Doses are measured in millisievert (mSv) but it is really just the relative dose sizes that we need to watch. Here are a couple of reasonably obvious principles to keep in mind:
- ‣ bigger doses should be more damaging than smaller ones;
- ‣ for doses of the same size, those received over a longer period leave more opportunity for repair and so should be less, not more, damaging.
Here then are some facts (details can be found in publications, some popular and some more technical, from http://www.radiationandreason.com):
1. The average dose received from natural sources of radiation in a month is about 0.2mSv. This includes radiation from space, from internal radioactivity spread through the body, from rocks and from breathing in radon, the radioactive gas released in the decay of uranium. It varies quite a lot from place to place but that seems to have no effect on anybody’s health.
2. A typical dose from a CT scan is about 5-10mSv, received instantaneously. An isotope scan also gives an internal dose of about 5mSv spread over 2-3 hours (for a PET scan) or 10 hours (for a SPECT scan). Both types of scan are harmless unless you 10 or more scans in a month. Nobody is likely to reach that rate!
3. Radiation is one of the most effective ways to cure cancer. In a course of radiotherapy very high doses indeed (more than 50,000mSv, note the number) are given to the cancer tumour itself over 4-6 weeks, and that dose kills the offending cells. Sometimes the radiation is given internally by an inserted radioactive source, and sometimes externally by gamma beam – both are effective. The choice may depend on the tumour and discussion with the patient. Significantly, gamma radiation cannot be focussed and in most current treatments a large dose (like 50%) is also given to organs and tissue five inches or more away from the targeted cancer. In most families or groups at least one member has survived such treatment (20,000mSv in a month) to organs that have given further beneficial years of life. This is a high monthly dose, but no “nuclear debate” or enquiry is needed to show that vital organs usually survive it. A century of medical experience has shown that it is essential that the dose is spread daily over a month to allow these healthy cells to recover each day.
4. The initial fire-fighters at Chernobyl received high doses within a couple of days. There were 42 with doses above 4,000mSv of whom 27 died in a few weeks from the radiation although none of those (140) with a dose below 2,000mSv died in this way.
5. There is no reliable evidence to show that there was any other loss of life due to radiation at Chernobyl, with the exception of some cases of child thyroid cancer from radioactive iodine. Its short radioactive life and its high concentration in the thyroid explains why natural radiation protection was overwhelmed, just in this case. There were about 6,000 cases but only 15 deaths because thyroid cancer is treatable, often with internal radiation from a radioactive iodine source.
6. The nuclear bombs dropped on Hiroshima & Nagasaki in 1945 generated an exceptional blast and fire-storm. In addition there was a flash of gamma radiation and neutrons that was responsible for an increase in cancer years later. This fact added extra fear to the nuclear threat during the Cold War against the Soviets and was exploited in Hollywood movies. The data show that cancers only increased by 1 in 15 compared to other Japanese cities and the increased mortality in 50 years was less than the chance of being killed in a road traffic accident in that time. Those who got a dose below 100mSv show no evidence for any increase in cancers.
7. No resident or worker at Fukushima has received any damage to their health and the chances are that none will do so, even in the next 50 years. The recorded doses are too small compared to Hiroshima and Nagasaki to account for even one cancer (and are accumulated over a year in which repair will be effective anyway).
8. On 4 April 2011 at Fukushima 11,500 tonnes of radioactive water were released into the sea, creating a storm of public protest. A simple calculation shows that drinking a litre of this water every day for three months would give a dose equivalent to two CT scans – even that is an overestimate as it ignores repair. That would be quite harmless. At the time it was reported that the radioactivity was 100 times the “safety” regulation – and that was true, but that is because the regulation is crazy, a thousand times too cautious.
9. In July 2011 the Japanese Government announced food restriction on meat with activity greater than 500 becquerels per kilo. My own calculation agrees with the Government who say that eating one kilo of condemned food would gives a dose of 0.008mSv over about 3 months. So a harmless CT scan (8mSv) gives the same dose as eating 1 tonne (8 divided by 0.008 kilo) – so the regulation is ridiculous! What happened then? In April 2012 the regulation was tightened — now eating FIVE tonnes of “contaminated” food is the same as a CT scan. Why did they do that? Popular pressure from frightened parents, the result of putting fear before science. The economic effect on this agricultural region in Japan have been devastating. In Scandinavia after Chernobyl similar regulations were introduced but after 6 months they were relaxed by a factor ten, not tightened as at Fukushima.
10. Evacuation at Fukushima was also guided by harmful regulation, based on a maximum recommended monthly dose of 2 mSv (20mSv a year). This could have been relaxed 60 times without harm from radiation and with enormous benefit to public health and the economy by reducing stress, suicides, bankruptcies, premature death among the elderly and distress and bed-wetting among the young.
Let’s make choices that help us to survive
Each year the weather varies and the popular chatter about climate change continues in the media. But the significant stories are the steady relentless increase in atmospheric carbon dioxide and the remarkable shrinkage of polar ice. These should be alarming to everybody. Meanwhile business interests try to persuade the world that natural gas is much better than coal (only slightly), that biofuels provide an answer (but that is just throwing carbon dioxide that has been captured by plants right back into the atmosphere) and that other green energy can provide a sufficient solution (unlikely, especially when the consumer finds out the full cost).
This agonising is unnecessary – nature has already provided the perfect carbon-free solution with extraordinary natural safety. Of course nuclear power can be made (and already is) undeservedly expensive by loading it with daft safety requirements. As demonstrated at Fukushima these bring unsubstantiated fear that itself causes severe stress and loss of life. This was already well described after the Chernobyl accident but nobody in Japan or the international regulatory authorities seems to have bothered to read it or thought that it was their job to act on it. The world press prefers the imaginary shock-horror stories of radiation which political opinion then seems simply to accept without question.
For example, fiction relishes the description of plutonium, the nuclear fuel, as the most dangerous substance on the planet. But this fiction is too often seen as reality, oblivious of the fact that those who have worked with plutonium seem to live longer than others. There is a photograph of Queen Elizabeth being handed a plastic bag of plutonium in the 1950s and being invited to feel its warmth. She too is enjoying long life, unharmed by the experience. The most dangerous material on Earth is arguably oxygen, responsible for the destructive runaway chain reaction we call fire that throws its polluting waste into the atmosphere. Only fear itself is more destructive – like the fear that persuaded 1800 additional women to have abortions following Chernobyl, and that was just from one country, Greece, for which the data are well documented.
There is a choice of different nuclear technologies, and some groups are eager to defend the merits of one rather than another. The truth is that there may be a mix and the details do not matter to the big picture. However unlikely, another accident or two like Fukushima or even Chernobyl, would still leave nuclear much safer than any other energy source like oil or coal, and radiation is a small local safety hazard, at worst – thanks, as we have seen, to the natural protection by biology. But evolutionary biology has not prepared us at all for the big global safety hazards – population, climate change, social and economic instability, shortages of food and water – and man’s supposed intelligence is not currently adequately engaged either. We owe it to those who come after to convert to nuclear power. And safety? The plants have to be safe and stable from an engineering point of view, but concern about radiation and health is a matter for education and individual common sense. Slow moving self-perpetuating international committees should not be involved. We live without them for ultraviolet radiation, the ionising component of sunshine that can cause sunburn and skin cancer. When we go on holiday we enjoy the Sun’s rays with personal care and responsibility — and public opinion eagerly promotes this alongside the Sea and the Sand! It is high time that we welcomed other forms of ionising radiation as readily.