What is "spallation"

n. 1 (context nuclear physics English) A nuclear reaction in which a nucleus fragments into many nucleons. 2 fragmentation due to stress or impact.

n. (physics) a nuclear reaction in which a bombarded nucleus breaks up into many particles; "some astronomers believe that the solar system was formed by spallation when the sun was a very young star"

Spallation is a process in which fragments of material ( spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection or vaporization of material from a target during impact by a projectile. In planetary physics, spallation describes meteoritic impacts on a planetary surface and the effects of a stellar wind on a planetary atmosphere. In the context of mining or geology, spallation can refer to pieces of rock breaking off a rock face due to the internal stresses in the rock; it commonly occurs on mine shaft walls. In the context of anthropology, spallation is a process used to make stone tools such as arrowheads by knapping. In nuclear physics, spallation is the process in which a heavy nucleus emits a large number of nucleons as a result of being hit by a high-energy particle, thus greatly reducing its atomic weight.