The facts of the meltdowns of reactors at Fukushima Daiichi on 11th March 2011 and their aftermath have been covered in detail elsewhere, for example in the Wikipedia article on the subject, the World Health Organisation and UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reports on the accident, and the English language report of the independent commission set up to investigate the accident.
Although the Fukushima accident caused a mess which is time consuming and expensive to clean up, it caused remarkably little harm to people directly, especially considering that it was the worst civil nuclear reactor accident after Chernobyl. What is extraordinary is how much harm has been caused, not by the accident itself but by actions resulting from excessive fears of radiation: Radiophobia. These harms are continuing and getting worse every day.
Initially these fears resulted in far more people being evacuated from a far wider area than necessary. This resulted in the deaths of between about 600 and 2000 people (estimates vary) due to evacuation and relocation, including sick and elderly people moved from care homes and hospitals in the evacuation zones. In the enormous disruption caused by the earthquake and tsunami it is understandable that response to the Fukushima accident would have been chaotic, especially as this was the first severe nuclear power station accident outside the former Soviet Union for over 30 years; since Three Mile Island in the USA in 1979, where evacuation was contemplated but not carried out. Recent studies have shown that not only in Fukushima but even at Chernobyl, evacuation was largely a mistake, causing far more harm than it averted.
However even these few hundred or thousand deaths are dwarfed by the greater harms caused by response to the accident.
For many decades nuclear energy has been opposed by an increasingly powerful anti-nuclear movement, including multinationals such as Greenpeace, Friends of the Earth, and most Green Parties, the Sierra Club in the USA, and others. (It was not always so; in the 1960s many environmentalists regarded nuclear energy as a benign alternative to hydro-electric schemes which flooded vast habitats and disrupted ecological systems, but that gradually changed, and the foundation of Friends of the Earth, with a donation of the then huge sum of $80,000 from an oil industry patron, helped turn the environmental movement towards anti-nuclear activism.) Nuclear accidents - Three Mile Island in the USA in 1979 (conveniently coincidental with the release of a conspiracy/disaster Hollywood movie set in a nuclear power plant), Chernobyl in 1986, and Fukushima in 2011 - have, despite their relative or absolute lack of lethality, provided powerful ammunition for the anti-nuclear cause, and been exploited ruthlessly.
A classic example of anti-nuclear propaganda about Fukushima is the misuse of a NOAA (US National Oceanic and Atmospheric Administration) map showing heights of the tsunami wave at various points around the pacific Ocean by anti-nuclear / conspiracy / alt-med websites which claim that it shows radiation levels from the accident.
Some sites don't even bother to crop the picture to exclude the tell-tale key (at the bottom-right, over South America), showing centimetres of wave height.
Another is attributing this image of a fire at the oil refinery in Ichinara City in Chiba Prefecture to Fukushima.
There have also been (scientifically unfounded) claims that radiation detected at trace levels on the West coast of the USA and Canada is having devastating effects on fish or even humans.
Whilst these sort of propaganda, like COVID-19 denial, anti-mask, anti-vaccine and Qanon conspiracy theories are extreme and clearly unscientific, they possibly nurture more widespread but still counter-factual beliefs that nuclear energy is particularly dangerous rather than, in fact, one of the safest forms of energy we have:
This widespread fear of nuclear energy helped the anti-nuclear movement in Germany gain the power to drive Germany's committment to close all its nuclear power plants. The policy widely referred to simply as "Energiewende" ("Energy transition") is actually in full "Energiewende – Atomausstieg und Klimaschutz": "Energy Transition: Nuclear Phase-Out and Climate Protection", and the Nuclear Phase-Out part has clearly been the major component of the policy, with Climate Protection very much secondary to the ideological goal of shutting down nuclear.
Despite having spent over 150 billion Euros by 2016 on renewables Germany has been re-building coal-fired power stations, and destroying ancient forests and villages to extract more and more Lignite - brown coal: the dirtiest form of this dirtiest of fossil fuels - to supply them.
The air pollution they produce kills more than 4,000 people every year, 1,100 a year due to the as-yet only partial nuclear shut down which is calculated to have increased local air pollution by around 12% and to be costing the German economy about 12 billion dollars a year. Germany has set an extremely unambitious target of phasing out coal by 2038 and, whilst they claim that they will replace lost capacity with renewables, Chancellor Angel Merkel has admitted that if we phase out coal and nuclear energy, then we have to be honest and tell people that we’ll need more natural gas”.
The Fukushima accident - one of many results of the destruction caused by a natural disaster of almost unprecedented violence - had a death toll of approximately zero. Yet Japan's reaction to it has killed a similar number of people, through increased air pollution, as the Great East Japan Earthquake and Tsunami itself did. Germany is inflicting roughly double Japan's number of deaths on its own - and its neighbours' - citizens, and is pushing ahead with plans which will kill yet more, and the USA and other countries are committing to similar self-harm.
None of these deadly figures includes the toll of death and destruction which will be visited disproportionately on the poorest and most vulnerable of our global fellow-citizens, and on our and their children and childrens' children, through the climate change effects of nuclear shutdowns.