For years, and then after the explosion too. The last reactors were decommissioned around 2015 (it takes years, so the dates are bit washy).
Chernobyl wasn't the accident people seem to think. It wasn't inevitable, it was the result of numerous self-serving decisions exacerbated and even required in the very messed up Soviet system of management that enforced following the party instructions over all other possible complications.
Unfortunately they have a point, in that there is no ISO or DIN standard that covers a plant that has been rigged with explosives by invading barbarians.
The solution isn't to abandon nuclear power, but to make it very costly for aggressors to meddle with it. E.g., deploy UN forces to the plant at the first sign of trouble.
