In a lump of uranium-235, one nucleus splits and releases three neutrons. Nearby nuclei absorb them and split in turn. Nobody adds anything from outside, yet the splitting spreads, and keeps spreading.
In the last lesson you saw nuclear fission: a heavy nucleus, usually after absorbing a neutron, splits into two smaller nuclei and releases two or three fresh neutrons. This lesson is about what those fresh neutrons can start.
One fission releases two or three fresh neutrons.
Nearby heavy nuclei absorb those neutrons.
Each absorbing nucleus splits in turn.
Each new fission releases more neutrons, so the reaction keeps itself going.
In a lump of uranium-235, the three neutrons from one fission can trigger up to three more fissions.
Each of those fissions releases three more neutrons, so up to nine fissions can follow them.
No outside supply keeps a chain reaction going; each round of fissions starts the next.
In a lump of uranium-235, one fission releases three neutrons. Nearby nuclei absorb two of them and split; the third neutron escapes the lump. How many fissions does this next round have?
A new fission happens where a nucleus absorbs a neutron and splits.
Two of the three neutrons are absorbed by nuclei that then split.
The escaped neutron triggers nothing.
The next round has two fissions.
What keeps a chain reaction going once it has started?
Each fission releases two or three fresh neutrons.
Nearby heavy nuclei absorb those neutrons and split in turn.
Each new fission releases more neutrons, so the next round of fissions follows.
The fissions themselves supply the neutrons for the next fissions. Nothing from outside is needed.
In a chain reaction, what triggers the fissions after the first one?
One fission in a lump of uranium-235 releases three neutrons, which drift through the lump. At most, how many new fissions can those three neutrons trigger?
Ranya says: 'A chain reaction keeps itself going, because each fission releases neutrons that trigger more fissions.' Is Ranya correct?
Which statement describes a fission chain reaction?
In a power station, fissions continue in the uranium fuel for months, with no neutrons supplied from outside. Where do the triggering neutrons come from?
What do we call a nuclear reaction that keeps itself going because each fission's neutrons trigger more fissions?