The Fukushima and Three Mile Island nuclear power plant accidents have a number of similarities. These include western design, releases of radioactivity resulting in no measurable health effects and constrained operation under some form of regulated safety oversight.
The Chernobyl event was caused by a number of undesirable factors occurring at the same time . This included a poor design and quite a few poor operational practices at the time of the event. The reactor core itself was largely made of a flammable material (effectively charcoal briquettes) so that a meltdown resulted in the core catching fire and releasing very large amounts of radioactivity. The operators were conducting unapproved tests under conditions which would have failed standard safety reviews had they been utilized. The Chernobyl reactor was operated in such a way that the water coolant was caused to flash into steam which in turn burst the reactor vessel preventing the water coolant from passing through the core. This left the core without any forced heat removal capabilities so that once the core caught fire, things got substantially worse. Dozens of first responders were exposed to enough radiation to cause them to succumb to acute radiation syndrome and eventually death. There was also a measurable increase in childhood thyroid cancers due to the initial government cover up and lack of radioprotectant iodine pills being distributed to the public (these only protect people from ingesting radioactive iodine). No other cancers have been identified which could be scientifically identified as being (with statistical significance) caused by the Chernobyl accident.
The Three Mile Island event did result in some core damage from melting and released a relatively small amount of radioactivity. This event was a combined effect of poor training accompanying design issues allowing operator misinterpretation of readings. The event resulted in major changes to the safety requirements for all US nuclear power plants along with substantial improvements to safety analysis of nuclear facilities as well as to the federal radiological emergency response system.
The Fukushima event also had design shortcomings, it was built to withstand earthquakes and tsunamis (tidal waves) but only held up to the earthquake. The tsunami was substantially bigger than what was predicted and so took out far more infrastructure than the facility could withstand. The explosions at the Fukushima plant were due to elemental hydrogen created through a catalytic reaction with the fuel cladding under extreme heat. The eventual radioactivity releases were predominantly directed out toward the ocean with the portion depositing on the island not being sufficient to cause any measurable health effects.
One common theme in all of these accidents is that in general, health consequences are not global and unless you are up close and personal with the reactor core, health effects are not noticeable in any measurable way. The thyroid cancers from Chernobyl are the only exception to this and did produce some measurable offsite consequences. These particular cancers can be attributed to gross negligence in the emergency response efforts from the Soviet government as they were only focused on the reactor and sadly, these were preventable. All the Soviet government had to do was to evacuate and/or distribute iodine pills to the public and so block uptake of the radioactive iodine released from the accident.
Another common theme in these accidents was the inability to remove heat from the reactor core. The reactor in a nuclear power plant is the main functional difference between it and any fossil fuel power plant. The reactor in a fossil fuel power plant burns hydrocarbons (oil, coal or natural gas) to produce heat sufficient to vaporize water which then turns a turbine to produce electricity. With a nuclear power plant, the heat is no longer produced by traditional fire but rather by splitting atoms. The functional difference in this context is that fossil fuels don’t stay thermally hot long after they are burned, nuclear fuel on the other hand does. Nuclear fuel is full of fission products which give off energy as they undergo radioactive decay. This energy is quickly converted to heat resulting in rather long term heat production from the fuel even after it is no longer effectively useful as fuel. This means that even when a nuclear reactor is turned off (i.e., the fission chain reaction is no longer taking place), large amounts of heat are still being generated in the fuel and must be removed if the fuel is to remain below its melting point temperature. These 3 events, Three Mile Island, Chernobyl and Fukushima all underwent this type of catastrophic failure of reactor core damage resulting in environmental releases of radioactivity.
Worldwide, the amount of radioactivity these have caused are actually only a small fraction of that which is present in the environment due to historic atmospheric nuclear weapons tests carried out by ours and other countries. The typical dose the average American receives from having all of the man made radioactivity in the environment is really only a very small fraction of that received due to natural radioactivity such as potassium, thorium and radon.
When comparing these to industrial failures at other factories or production plants, do any of these rise to the occasion of an actual disaster?