spontane fu'ivla

x1 is spontaneous in property x2 (ka)

In definition:

rarna
x1 is natural/spontaneous/instinctive, not [consciously] caused by person(s).
spaune
x1 (individual/entity/result) abruptly (re)spawns/appears/becomes/comes into being/existence/life by mechanism/under conditions x2; x2 spontaneously generates x1

In notes:

ratypo'i
r1=p1 undergoes nuclear fission