In November 2011, eight months after the Fukushima Daiichi Nuclear disaster, I travelled with Japanese colleagues to Iitate, a village some 50 kilometres from the stricken power plant._

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Our route took us through landscapes of empty fields and deserted houses, interspersed with shuttered shops and abandoned cars.

Iitate was a ghost town. Of its 6000-plus inhabitants, only 13 remained. The rest were living in temporary accommodation in other parts of Fukushima Prefecture and beyond. Five years later, just a few hundred had returned. Since then, the return flow has gradually gathered pace, but 14 years on, some 29,000 people from the disaster area as a whole remain displaced. The area’s landscape is still littered with mountains of radioactive waste, and contaminated water will continue to be released from the ruined plant for at least another 30 years.

The Australian debate about nuclear power has so far focused heavily on cost and construction timelines. “Nuclear energy” has been reassuringly rebranded “zero emissions nuclear energy” – a phrase which begs the question: “zero emissions of what?” Nuclear power plants may not emit carbon dioxide, but Fukushima residents remind us that there are other emissions whose complex and enduring impact needs to be much more widely understood.

Risk and uncertainty

Despite the bad publicity generated by Three Mile Island (1979), Chernobyl (1986) and Fukushima (2011), many experts insist that nuclear, alongside wind and solar, is one of the safest sources of power, in terms of number of deaths per kilowatt of electricity generated. So, how many people died as a result of the Fukushima nuclear meltdown? The Japanese Government acknowledges just one death of a nuclear worker as a direct result of the radiation, but also gives a figure of 3794 recognised “ indirect deaths”, caused by the mental and physical stresses of the mass evacuation following the tsunami and meltdown. That latter figure, though, is imprecise; and no-one has produced a reliable estimate of the number of “indirect deaths” caused by the mass evacuation of some 200,000 people after the Chernobyl disaster.

The correct answer to the question about the number of Fukushima-related (and Chernobyl-related) deaths is: “we will never know”. The science which can design extremely complex nuclear reactors has not yet developed the skills to produce any clear answer to the question “what are the health (and death) risks of prolonged exposure to substantially raised levels of radiation?”

Short-term exposure to massive doses of radiation, like those experienced by first responders at Chernobyl, produces readily visible effects. Many studies also suggest that long-term exposure to much lower, but still elevated, levels of radiation may increase the risk of birth defects, and of a range of potentially fatal illness including leukaemia and other cancers and heart disease.

But these consequences appear only gradually, and are spread amongst large populations, making it extremely difficult to distinguish them from illnesses triggered by other environmental factors. Unless individuals wear a radiation monitoring badge 24 hours a day for years, it is also impossible accurately to determine their cumulative exposure to radiation, because local radiation levels in affected regions can vary greatly within a very small area.

The children of Fukushima

One health impact of radiation that can relatively readily be identified is childhood thyroid cancer, which is very rare in the general population. In the case of Chernobyl, about 7000 children developed thyroid cancer as a result of radiation. Only a small number died, because the disease it treatable, but the treatment is painful and life-altering.

But even with thyroid cancer, the issue of uncertainty remains, as illustrated by a fierce controversy surrounding an apparent spike in childhood thyroid cancer in Fukushima. Soon after the accident, health authorities started a screening program for children in the affected areas. By 2023, 295 children had been diagnosed with thyroid cancer (with 43 more diagnosed outside the screening program): more than 15 times the incidence of thyroid cancer in the wider population. Some scientists insist that it is just the result of the "screening effect" – i.e., cases which would otherwise have been identified only later in life are showing up early because of intensive screening. But others argue that, although the screening effect does explain part of the increase, it does not explain why new cases keep appearing as the same cohort is tested over the years; nor does it explain apparent correlations between levels radiation exposure and thyroid cancers.

These life-changing and uncertain risks are completely different in nature from the clearly-defined risks of wind or solar power generation. Accidents in wind and solar generation do not cause mass evacuations; nor do they leave workers and local residents struggling with the uncertain and frightening prospects of potentially serious ongoing health problems. Almost all wind power-related deaths are road or industrial accidents during the construction phase, while most solar-related deaths are accidents occurring during the manufacturing or installation of components.

The data collection methods used in rankings of “safe sources of electricity” do not even comprehensively cover fatalities occurring during the construction of complex nuclear plants and their components. They have no way of fully reflecting deaths and illnesses resulting from exposure of workers and the general population to radiation. These attractively simple statistical rankings create a smokescreen obscuring the health uncertainties which make nuclear power such a very different proposition to renewables like wind or solar power.

Australia does not have earthquakes or tsunamis on the Japanese scale. But the root cause of the Fukushima disaster was not the earthquake or tsunami. It was a failure of risk assessment: the plant’s designers and managers underestimated the possible size of a tsunami, and built a sea wall which was too low to protect the plant when disaster struck. It would be sheer arrogance to claim that a failure of risk assessment could not happen in other countries, including Australia. The ongoing, harrowing experiences of the people of Fukushima should be at the centre of any debate about nuclear power.