Nobody is saying that nuclear reactors are perfectly safe, but as the BP leak showed, nothing is perfectly safe. The Chernobyl and Fukushima reactors were designed back in the sixties with a horrific lack of fail safes. A modern plant would be much safer given the superior understanding of previous failure modes, advances in material sciences, and computer aid in simulating operations and design.
Hell, Chernobyl was a graphite moderated light water reactor. These reactors were designed so that they could be refueled while the plant was running. This was useful because if you left the nuclear fuel rods in there for too long, then the fissile P-239 that could be used for bombs would become P-240, which was a poison to bombs. In short, Chernobyl was designed to make fuel, not to be safe.
Fukushima was flawed in that it would require active cooling for three days after full shut down in order to be safe. Reactor 1 had a passive cooling system that relied on convection to keep the fuel at a safe temperature. An operator turned off the passive cooling system before the tsunami hit, and wasn't able to turn it on after the tsunami strike knocked out the backup generators. Newer designs provide passive cooling for up for 72 hours after a shut down.
There is no safe way to make energy. Coal mining kills many people. BP leaked tons of oil while drilling. You cannot judge nuclear power by the failure of old technologies whose flaws have been addressed in newer designs.