Remarks delivered by Tilman Ruff, 26 April 2025 (updated 28 April)
“Thorough studies conducted in the Soviet Union have proved completely nuclear power plants to not affect the health of the population.” Lev Feoktistov, deputy director of the Kurchatov nuclear energy Institute 1985
“Nuclear power is the safest form of energy yet known to man.” UK energy Minister Peter Walker, 16 March 1986*
On this day 39 years ago the worst nuclear accident so far exploded in Reactor 4 at the Chernobyl nuclear power plant. It was a Soviet-made RMBK, high-power channel reactor design that could produce plutonium for nuclear bombs as easily as it could produce electricity.
A major reason for the disaster was that those in Moscow who decided to re-purpose reactors originally designed to produce materials for nuclear weapons to produce electricity kept secret a good deal about the inherent design dangers and instability of the reactors even from the reactor operators (including its ‘positive void co-efficient of reactivity’). The operators with pressure to fill production quotas cut corners.
In the reactor, 1661 zirconium pressure tubes contained fuel rods and cooling water within 1700 tonnes of graphite and a complex system of control rods, without heavy engineered containment. The design was 20 years old, but the plant had only been operating for three years.
An experiment was conducted to determine how much electricity could be generated by the freewheeling turbine to which supply of steam from the reactor had been cut. The experiment was delayed by 12 hours but continued in the wee morning hours despite failure to reset the automatic control system.
Multiple safety rules were deliberately violated. Reactor power was lowered to prohibited levels before attempts were made to insert shutdown control rods into the reactor core. Because of an inherent flaw in the reactor design, this did not lead to powering down, but to a rapid explosive burst. Nuclear criticality increased rapidly in some fuel elements, leading to their explosive disintegration, generation of vast quantities of steam and a hydrogen explosion. Chunks of highly radioactive molten fuel were blasted 7 – 9 km into the air, much of it into the stratosphere. A burning plume extended 500 m high. The two explosions and graphite fire over the next 10 days ejected about one third of the 190 tonnes of fuel inside the reactor and radioactive material continue to be emitted for a month.
The World Health Organisation observed that the Chernobyl disaster released 200 times as much total radioactivity as the Hiroshima and Nagasaki atomic bombs.
Early fallout more than 1500 km away was first detected the following day when unusually high levels of radiation were measured when a nuclear power plant worker in Sweden was checking out of work. For a day and a half, nobody understood the full extent of the disaster. Initial attempts to put the fire out with water only worsened the situation. Evacuation of nearby residents was only implemented after 34 hours.
The first Soviet news report came at 9 pm on 28 April, the first Western news report following day. No one was prepared for a disaster of this magnitude.
116,000 people were initially evacuated, and 230,000 in the following years in the contaminated regions of Belarus and Ukraine. Some 350,000 people were resettled from the worst affected areas.
Up to 800,000 so-called ‘liquidators’, mostly young healthy firefighters and other emergency workers from across Soviet republics were involved in the disaster response, and control efforts. Half were military personnel, others were technicians, miners, pilots, drivers, firefighters and other emergency service workers. Many took significant personal risks without optimal protection. Now they have high rates of mental disorders, suicide, leukemia and other cancers.
5 million people live within the area where they were likely to receive an extra 1 mSv of radiation per year from caesium 137 alone. The contaminated areas of Ukraine, Belarus and Russia are home to 66.5 million people.
Extensive areas in Europe, particularly in the Alpine region and across Scandinavia, but extensively through the Balkans down to Greece; home to 570,000,000 people, were significantly contaminated. European countries then outside the Soviet Union received 37% of Chernobyl fallout. Contamination circled the northern hemisphere, extending to the Middle East, across Asia to Japan.
10,000 km² of land around the Chernobyl plant is still unusable for economic activity. Hotspots occur well outside the evacuation zones.
In the Chernobyl disaster, nuclear fuel from inside the reactor was blasted out, with hot particles falling down as far away as in several European countries. The worst contaminated areas are unlikely to be safely habitable for tens of thousands of years.
Radioactive caesium and strontium in particular accumulate up the food chain and are recycled by living organisms. They accumulate in water bodies and forests and these radioactive materials like caesium, strontium and plutonium are dispersed again in the smoke and ash from increasingly frequent and severe forest fires.
The collective effective lifetime dose of radiation from the disaster has been estimated at not much less than half a million person-Sievert, which by 2065 is conservatively estimated to result in over 17,000 thyroid cancers, most in children and young people, over 50,000 extra other cancers, about half of them fatal, at least the same number of extra chronic disease cases and deaths, excess birth defects and developmental abnormalities and neurological impairments across contaminated countries. Half the non-thyroid cancer cases are expected to occur outside Belarus, Russia and Ukraine.
A 1993 UNSCEAR report estimated the total collective dose as somewhat higher, at 600,000 person-sievert.** Applying the US National Academy of Sciences Biological Effects of Ionizing Radiation population cancer mortality estimates to this dose yields more cancer deaths – roughly 34,000, and around 70,000 total cancers.
In addition are major and long-lasting adverse effects on health from displacement, loss of livelihoods, homes, lands and communities, fear and uncertainty and impoverishment. Disruption, disadvantage, mental health stresses and their consequences of mental disorders, substance abuse and disrupted lives and families affect millions and cross generations.
A large body of evidence has been gathered in recent decades on the effects of radiation on non-human biota living in radioactively contaminated areas, particularly around Chernobyl and Fukushima. In virtually every species and ecological community studied―from soil bacteria and fungi through trees to various insects, spiders, amphibians, diverse birds, large and small mammals, and diverse coastal marine organisms―adverse biological effects have been found in direct proportion to the degree of radioactive contamination, without any apparent threshold, and with most effects apparent across the range of 1‒10 mGy per year. *** Injury is seen in individuals, populations, species, and ecosystems.
Animals in the wild have been shown to be about eight times more sensitive to radiation than previously thought largely on the basis of laboratory studies. And as for humans, the more we know the worse radiation effects look to be.
In plants, damage to DNA, reduced pollen viability and germination rates, impaired growth, abnormal growing tips, and abnormal leaf and overall plant size and morphology are seen.
In animals, effects include DNA and other types of genetic damage, physical abnormalities, tumours, cataracts, reduced brain size with impaired neurological development and behaviour, reduced fertility including absent or depleted, dead, abnormal and immotile sperm, reduced lifespan and reduced organism numbers and biodiversity. In the most contaminated areas around Chornobyl, there are only one-third as many birds and half as many species as one would expect. Chornobyl birds have more deformities, cataracts, smaller brains, impaired calls, are dumber, and don’t live as long. 40% of male birds have no sperm or only dead sperm.
It is biologically implausible that humans are immune from similar effects.
The other 3 similar reactors on site were operated until the last of them was shut down 14 years later in 2000. The original hastily built confinement structure over Reactor 4 had major structural problems and did not fully prevent continuing release of radiation into the atmosphere.
A second international project to construct a new sarcophagus took more than 25 years, costing €2.2 billion, producing the largest movable structure in the world, over 250 m long and weighing 36,000 tonnes. Yet it’s expected lifespan is only 100 years, less than one half of 1% of one half-life of plutonium-239.
The nuclear reactions in the heart of the damaged reactor fuel are far from over. In 2021 a spike in neutron emissions first noticed in 2017 was measured underground near the radioactive fuel debris. There is concern that it could be the harbinger of escalating criticality in the 200 tonnes of highly radioactive material including fuel remaining under where the reactor used to be.
A second Chernobyl crisis began in 2022, when at the very start of Russia’s large-scale invasion of Ukraine, the plant was attacked, occupied and used as a military base by Russian forces.**** The occupying forces used the Chernobyl plant as cover for their invasion, holding plant staff hostage, turning it into a fortress, establishing firing positions, and digging fortifications in some of the most contaminated areas.
All Ukraine’s 6 nuclear power plants have been attacked by Russian forces in the current war. Most alarmingly at the Zaporizhzhya nuclear power plant in southern Ukraine, Russian attackers fired on and shelled the planned, set a training centre ablaze, damaged the administration building as well as spent fuel facility, sowed landmines, terrorised plant staff, and used it as cover to attack the neighbouring town and surrounding areas with artillery fire. They further took the extraordinary dangerous step of bombing the Kharkova Dam, joepardising the final reservoir of cooling water for Europe’s largest nuclear plant, as well as causing extensive flooding and pollution downstream.
The International Atomic Energy Agency Ukraine update from 24 April 2025, just 2 days ago, described loud bursts of gunfire from near the main administrative building at Zaporizhzhya, the team there hearing explosions and gunfire at varying distances from the plant almost every day during the past week.
This widespread targetting and holding hostage operating nuclear reactors in war has plainly demonstrated not only the threats posed by nations violating the UN Charter and international law, but also the lack of any effective international means to protect nuclear facilities from military attack, and how quickly atoms ostensibly for peace can be turned into atoms for war. Each nuclear reactor and spent fuel pond is effectively a massive pre-positioned radiological dispersal device, or ‘dirty bomb‘.
At the IPPNW Congress in Germany a few weeks after the disaster, I heard senior Russian doctors, including some overseeing the emergency medical response to the disaster, sleep-deprived and exhausted, speak unforgettably about how this one non-nuclear explosion in a single nuclear power reactor stretched to the limit medical resources and emergency capacities of a large country, and affected the entire continent of Europe.
I express my sympathy for the many victims of this ongoing disaster, past, present and future.
20 years after the disaster, then Soviet president Mikhail Gorbachev wrote: “The price of the Chernobyl catastrophe was overwhelming, not only in human terms, but also economically. Even today, the legacy of Chernobyl affects the economies of Russia, Ukraine and Belarus.”
He wrote: “Chernobyl opened my eyes like nothing else: it showed the horrible consequences of nuclear power even when it is used for non-military purposes.”
He said that: “The nuclear meltdown at Chernobyl, … even more than my launch of perestroika, was perhaps the real cause of the collapse of the Soviet Union five years later.”
Nuclear reactors may produce useful electricity for a brief few decades, but their enduring products are uniquely hazardous radiation and high-level radioactive waste which persist over geological time frames.
39 years is a little over one half-life of caesium 137, so the cesium-137 in fallout across the world will by now have decayed by a little over half.
The plutonium 239 released however with a half-life of 24,400 years, will have only decayed by one seventh of 1% by now. It will take a quarter of a million years for it to substantially decay away.
The misguided arrogant and dangerous hubris and vested interests that brought us the Chornobyl and Fukushima disasters, and at least 11 other core melt accidents in different nuclear reactors, now brings us the wilful madness of the alternative parties of Australian government’s plan for nuclear reactors proliferated around our wide, sunny and windy land. If we don’t act on evidence and learn from the past, we will be doomed to repeat it.
* Both quoted in Hawkes N, Lean G, Leigh D, et al. The worst accident in the world. London, William Heinemann, Pan Books, The Observer, 1986:1,41.
**UNSCEAR. Sources and Effects of Ionizing Radiation: UNSCEAR 1993 Report to the General Assembly, with Scientific Annexes (New York: United Nations Scientific Committee on the Effects of Atomic Radiation, United Nations, 1993):23.
**Mousseau TA. The biology of Chernobyl. Annual Review of Ecology, Evolution, and Systematics, Vol. 52 (2021), 87–109.
****A useful account of this added crisis is: Plokhy S. Chernobyl roulette. Allen Lane 2024.