How many neutrons are typically released during fission?

• A. Two to three other neutrons are released along with heat and radiation.
• B. Ten neutrons are released.
• C. No neutrons are released.
• D. Exactly one neutron is released always.

Answer: (A)

In fission, a heavy nucleus splits into two lighter fragments and releases several neutrons along with energy. The number of neutrons emitted in a single fission event isn’t a fixed value, but the average prompt neutron multiplicity is about 2 to 3. In other words, most fission events produce two or three neutrons right away, with the average around 2.5. These prompt neutrons are the ones that drive chain reactions in reactors because they can initiate further fissions in neighboring nuclei.

There are also neutrons released later, from the decay of fission fragments (delayed neutrons), but those occur after the initial fission event and are separate in time from the immediate fission neutrons. The key point for the question is the typical prompt neutron count, which is around two to three.