I am of the opinion that people are just plain stupid. Nuclear plants can be made and run safely, but you have to trust that the contractors built the plant without any cost-saving shortcuts and that the managers of the plant actually have enough brains to run the plant safely.
3 mile and Chernobyl were functional plants with enough safeguards in place to run safely but we are forced to trust plant managers to run them safely. It also requires complete honesty when a problem occurs so proper steps can be taken, or the safeguards are useless.
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By design, the Chernobyl plant did not even have a containment building...like the building that exploded in Japan.
After the 3 Mile Island near disaster, they did add a partial containment building, but it's very design required large cranes to be used above the core, so a full containment building would have gotten in the way.
This, from a wiki source:
Initially, the RBMK design focused solely on accident prevention and mitigation, not on containment of severe accidents. However, since the Three Mile Island accident, RBMK design also includes a partial containment structure (not a full containment building) for dealing with emergencies. The pipes underneath the reactor are sealed inside leak-tight boxes containing a large amount of water. If these pipes leak or burst, the radioactive material is trapped by the water inside these boxes. However, RBMK reactors were designed to allow fuel rods to be changed without shutting down (as in the pressurized heavy water CANDU reactor), both for refueling and for plutonium production (for nuclear weapons). This required large cranes above the core. As the RBMK reactor is very tall (about 7 metres), the cost and difficulty of building a heavy containment structure prevented building of additional emergency containment structure for pipes on top of the reactor. In the Chernobyl accident, the pressure rose to levels high enough to blow the top off the reactor, breaking open these pipes in the process.
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The Chernobyl plants were known to be extremely unstable when running at low power settings, yet they decided to do an experiment to see how long the plant's turbines' inertia could produce power if the main electrical supply was cut. They deactivated automatic shutdown mechanisms to carry out the experiment. During the experiment the coolant system failed and that doomed the plant.
Poor design, yes, but human error or rather decisions caused the disaster at Chernobyl.
http://www.heritage.org/research/rep...ctors-are-safe
http://en.wikipedia.org/wiki/RBMK#Containment