Question

what must a uranium-235 nucleus absorb before fission will happen​

Answer 1

Answer:

The arrangement of particles within uranium-235 is somewhat unstable and the nucleus can disintegrate if it is excited by an outside source. When a U-235 nucleus absorbs an extra neutron, it quickly breaks into two parts. This process is known as fission

Answer 2

Answer:

a nuetron

Explanation:

In a nuclear reactor , a neutron is absorbed into a nucleus (typically uranium-235). ... The fast moving neutrons carry most of the energy from the reaction with them (99%) but before the neutrons can collide with fresh uranium nuclei, they need to be slowed down