There will never be a completely safe man-made system.

For example, when designing a system for Functional Safety[0], none of the applicable standards (IEC 61508, ISO 13849, etc.) require that the product eliminate risk completely, because that is literally impossible in any complex system.

Instead, you reduce the risk based on the expected harm according to the function "[likelihood of dangerous incident / time unit] * [amount of harm caused if dangerous incident occurs]" until that expected harm is below a certain threshold.

Even accounting for Chernobyl, Fukushima, Three Mile Island, etc., nuclear already outperforms other sources of centralized power generation when you measure the deaths per unit energy produced[1]. Politically, the public may never accept this simple truth, because we are afraid of "big" things far out of proportion to their average actual danger to us. But it is a simple truth nonetheless.

[0]https://en.wikipedia.org/wiki/Functional_safety

[1]http://www.nextbigfuture.com/2011/03/deaths-per-twh-by-energ...