In fact, the reverse is the case. Per TW-year of electricity generated, the figures are: for 0.04 deaths for nuclear, 1.4 for hydropower and 160 for coal-fired generation. (New Zealand generates about 0.005 TW-year of electricity per year.)
Large hydropower needs large dams – much larger than any in New Zealand – and they pose a major long-term threat to the environment and populations downstream.
The biggest problems are a consequence of their long life that it is simply not possible to abandon a large dam because there is no way of safely draining and removing it.
When a large dam is built there is an unstated assumption that, for as long as the dam lasts, people will be available with sufficient expertise to monitor the dam and that they will have sufficient resources to carry out necessary maintenance and, occasionally, major repairs. As the dams could easily last for 1000 years or more, this is a very bold assumption.
Dams must survive earthquakes, floods, progressive leakage, concrete decay, foundation problems and serious erosion from the effect of spillway discharges that can – as has happened at Kariba in Africa already – put the whole structure of the dam at risk. If any of these things happen they require immediate attention from engineering and geological experts and, in many cases, the expenditure of hundreds of millions of dollars. If this does not happen, the dam will fail. In the case of Kariba, which will fail if nothing is done, three years worth of accumulated water would flow down the river in the space of a week or so. The 3.8 million people living in the Zambezi delta would be at risk of drowning or starvation.
Over the last 40 years or so hundreds of thousands of people have died from dam failures. At Banquio in China in the 1970s more than 100,000 people died from drowning and starvation when a dam with an undersized spillway failed during a flood. A few years later Machhu 2 dam in India also failed because of an undersized spillway and killed about 10,000 people. The government did everything it could to cover-up the failure and, in spite of evidence of serious negligence, no one was held to account.
I believe that the international dam industry needs to take urgent steps to improve short-term and long-term safety. If they do not, the chances of a catastrophic dam failure will continue to be high.
Chernobyl is the only nuclear power station that has killed people from radiation. It was a technically obsolete station with grossly inadequate safety precautions that was maloperated with many safety devices shutdown. About 60 people died from radiation sickness and preventable thyroid cancer over the next few years. Several thousand people might have their lives shortened by an earlier onset of cancer than otherwise would have occurred.
At Fukushima, United Nations experts have said that no one has died of radiation sickness and nobody will. The radiation levels they were exposed to were less than the natural radiation levels in several regions of the world.
At Chernobyl and Fukushima panic reaction by the authorities resulted in mass evacuations from regions without dangerous levels of radiation. At Chernobyl, something like 300,000 people people were dumped in what amounted to refugee camps and, almost literally, left to rot. The sudden disruption, social problems, alcohol and the like, killed or disabled something like 100,000. At Fukushima about 750 died from disruption and many people died from heatstroke caused by lack of air conditioning when the authorities shut down other perfectly safe reactors and caused major power shortages.