Which fact is true during a fission chain reaction?
During a fission chain reaction, one fact that is true is that each fission event releases multiple neutrons, which can then go on to cause further fission events. This creates a self-sustaining chain reaction.
To understand this fact, let's break it down step by step:
1. What is a fission chain reaction?
- A fission chain reaction is a process in which the nucleus of an atom is split into two or more smaller nuclei, releasing a large amount of energy. This reaction is initiated by bombarding the nucleus with a neutron.
2. Why do fission chain reactions occur?
- Fission chain reactions occur in certain isotopes (such as uranium-235 or plutonium-239) that are called fissile materials. These isotopes have the ability to undergo nuclear fission when struck by a low-energy (thermal) neutron.
3. How does the chain reaction happen?
- When a fissile material absorbs a neutron, it becomes unstable and splits into two smaller nuclei, along with releasing additional neutrons and a significant amount of energy. These released neutrons can then go on to strike and split other fissile nuclei nearby, creating a chain reaction.
4. What happens with the released neutrons?
- In each fission event, typically 2 to 3 neutrons are released. These neutrons are high-energy and can collide with other fissile atoms and cause them to undergo fission as well. This leads to a new release of neutrons, which can initiate further fission events, and the chain reaction continues.
5. How is the chain reaction controlled?
- To control a fission chain reaction, a material called a neutron moderator is used (such as water or graphite). The moderator slows down the fast neutrons produced in the fission so that they become thermal neutrons, which have a higher probability of being absorbed by fissile material and continuing the chain reaction. Control rods made of materials like boron or cadmium are also used to absorb excess neutrons and regulate the reaction.
In summary, during a fission chain reaction, each fission event releases multiple neutrons, which can then go on to cause further fission events, leading to a self-sustaining chain reaction.