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When things go wrong at a nuclear power plant, they can go very wrong. The reality is that outside of some high-profile disasters, nuclear power is extremely safe. But what does it mean when people say that a nuclear reactor is “fail-safe?”

YouTuber Randy Dobson has put together a quick little video explanation that demystifies the meaning of fail-safe when its applied to nuclear reactors.

The answer lies in some basic understanding of how a nuclear reaction is being created. Both nuclear weapons and nuclear reactors rely on fission to produce a powerful chain reaction. But in the case of a reactor, the stages of the process are carefully separated and the process is slower.

A key mechanism in the process for making nuclear power is the control rod assembly. These rods are made of chemical elements like boron that can absorb neutrons without getting caught up in the fissioning process. The control rods can be raised or lowered into the reactor to regulate the rate of fission. Electromagnets raise the control rods and hold them in place. In the event of a power outage, gravity will pull those rods down and shut off the fission process.

There’s more to the process of ensuring that a nuclear reactor is fail-safe but we have this handy video with visual aids right here. Click play and in just a few minutes you’ll feel a little better about that nearby power plant. And for an explanation of how these fail-safes can fail, here’s a good introduction.

[Randy Dobson/YouTube]