What is a nuclear SCRAM?

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In the movie *Shin Godzilla*, the humans came up with a blood coagulant and a plan to inject it into Godzilla in order to freeze him. It’s mentioned in the film that doing so would force him to perform a nuclear SCRAM since he’s fueled by an internal nuclear reactor. The coagulant works, shutting down his circulation (which is his cooling system), and causes him to freeze.

But what IS a nuclear SCRAM? i’ve looked it up before, but I just can’t seem to make heads or tails of it.

In: Physics

12 Answers

Anonymous 0 Comments

A scram is an emergency shutdown of a nuclear reactor. This can be caused automatically by reactor protection circuitry or can be manually initiated by an operator. When proper maintenance and procedures are followed, this will not cause damage to the reactor but instead will prevent damage from occurring.

A reactor works by using fission to produce heat. Fission is when a neutron collides with an atom of fuel, resulting in the atom splitting apart. This process generates heat, plus more neutrons that can go on to cause even more fission. Control rods are made of a material that is really good at absorbing neutrons. When control rods are inserted, most of the neutrons get absorbed by the control rods instead of causing fission. When control rods are withdrawn, some neutrons still get absorbed by the rods (and other things) but enough go on to cause fission to create enough heat to be useful.

So a scram is when control rods are inserted far enough into the core to make sure the reactor is shut down. Since it’s an emergency, this happens very quickly depending on how the reactor is designed. Think of a spring slamming the rods as far into the core as possible.

Some others have incorrectly stated that a scram would cause damage. This is not true. A scram in itself will not cause damage, but is designed to prevent damage from occurring.

Source: I’ve scrammed a reactor or two in my day.

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