At Chernobyl they messed up big time... The incident actually occured while performing an ill-planned test with some safety measures disabled.
Let's also remember a couple of other facts:
Chernobyl was in an office building, with no additional containment built around the reactor core.
Chernobyl was an outdated, graphite-modulated reactor. Several years prior to the disaster, German nuclear engineers had found that this reactor design would go uncontrollably critical if certain conditions were met. The Chernobyl engineers didn't know about this, thanks to the Soviet government.
And let's not forget that a large fraction of casualties after the Chernobyl accident is attributable to the fact that the general public was not informed for an entire day after the accident, in fact not until a powerplant in Sweden reported heightened radioactivity levels. This, with Kiev, Ukraine's multi-million capital, only 100km from Chernobyl.
The thing about nuclear power is that errors such as these have more serious consequences than for other sources of power. Or so it would appear.
But all this is relative: if nuclear power is the safest source of power, is there another source of power that is more dangerous than it?
Several of those disasters, of scales arguably larger than Chernobyl, were caused by attempts to generate power. And although I do not have any evidence to back this, I suspect the total number of casualties resulting from burning fossil fuels over the past century far exceeds that from nuclear power related accidents.
The one aspect of nuclear accidents I'd be willing to concede is the long-term contamination of the area, but while rendering chunks of land unusable, it is not a direct threat to life.
I'm sure you're correct on the fatalities for fossil fuel vs. nuclear, but fossil fuels are also much more widely used (I imagine by several orders of magnitude).
Making land unsafe is a less dramatic aspect of safety, but actually destroying usable land is an amazing feat of destruction. I guess if reactors were located on land that was already unusable (eg. desert, esp Antarctica) it wouldn't matter so much. But I think (present-day) electrical transmission requires them to be close to the power consumers?
True. Also consider the relative efficiency of the generation methods. Supplying the world's demand for energy with nuclear power would probably require far fewer powerplants than doing so by other means.
> I guess if reactors were located on land that was already unusable (eg. desert, esp Antarctica)
Except for the melting of the Antarctic ice and all that, in case of an accident :) Most technology seems to involve a trade-off of evils.
New dangers with nuclear power may be discovered (like those that those German researchers did), but that seems to be true also of new technology in dams and oil transport etc.