Are Nuclear Reactor Meltdowns as Bad as Nuclear Bombs?
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We’ve heard of many nuclear power plant disasters. Fukushima, Chernobyl, Three Mile Island are some names that come to mind. These seem to leave an impression — but what happens when a nuclear reactor melts down? Does it explode? Is it anything like a nuclear bomb?
Well, to understand why a nuclear reactor meltdown is very little like a nuclear detonation, we first have to understand the mechanism behind controlled and uncontrolled nuclear fission.
When a neutron collides with an atom, the atom becomes unstable and splits. When the atom splits, it releases energy, radiation, and more neutrons. Those neutrons can go on to collide with other atoms, causing them to split and release more neutrons that end up colliding with even more atoms, which release more neutrons, which split more atoms, you get the picture. This is called a chain reaction.
The chain reaction can be supercritical, critical, or subcritical. Whether a nuclear reaction falls into any of these categories depends on its multiplication factor (amount of neutrons produced divided by the number of neutrons absorbed). A multiplication factor greater than 1 means that the rate of the reaction is increasing; it is supercritical. A multiplication factor less than 1 means that the reaction rate is decreasing; it is subcritical. A multiplication factor of exactly 1 means that the reaction rate is stable; it is critical.
In a nuclear bomb, the nuclear reaction is not under control. It goes supercritical, and the reaction rate increases exponentially. Within a few milliseconds, all the energy stored in the bomb’s nuclear fuel is released.
On the other hand, a nuclear reactor employs control rods that absorb neutrons and keep the reaction critical — this allows the chain reaction to keep splitting atoms and producing energy that turns water to steam, which is then directed to turbines that spin and generate electricity.
But what happens if the nuclear reactor fuel goes supercritical? Does it explode like a nuclear bomb?
No. In fact, the nuclear fuel used by reactors doesn’t explode at all. When we hear about nuclear disasters where reactors exploded, the explosion being referred to is a steam explosion.
A nuclear reactor meltdown means that safety measures have failed, and the nuclear fuel itself has melted. If that happens, the steam in the nuclear reactor builds up and comes in contact with liquid metal causing an explosion.
That explosion is, of course, much less powerful than that of a nuclear bomb — it isn’t even a nuclear explosion. Every power plant has the potential to explode (as all power plants operate with energy-dense fuels).
Nuclear reactor fuel is only enriched up to 5%, while nuclear bomb fuel is enriched up to 90%. This means a nuclear reactor could never blow up like a nuke.
What makes nuclear reactor explosions so dangerous is the fact that they release radioactive material that contaminates the environment around them.
A nuclear bomb uses up all of its energy at once and spreads relatively little radioactive material over a large area. This contamination can clear up in a matter of decades. Whereas a nuclear reactor meltdown does not release all its energy at once, it leaves behind a lot of radioactive material over a relatively small area. This takes much longer to clear up.
Still, nuclear is an extremely safe energy source. A vast majority of nuclear reactors never see a meltdown that contaminates the environment around them, and even when they do, that space is less harmful to nature than human occupation.
Many of us fear nuclear power because of its association with nuclear weapons, but they’re nothing alike. Nuclear is a clean, environment friendly, and sustainable power source that is statistically safer than most, if not all, alternatives.
