Why This Stuff Costs $2700 Trillion Per Gram - Antimatter at CERN

6:13 From an old book my dad gave me after a conversation yesterday about nuclear reactors:

8.07 Negative-beta-particle Emission
Although free electrons do not exist inside the nucleus, a beta particle originates there and must pass the nuclear potential barrier to escape. A negatron, or negative-beta-particle, transition is the equivalent to the nuclear conversion
¹n → ¹p + e-

Lapp, Ralph E, and Andrews, Howard L. _Nuclear Radiation Physics,_ 4th ed. Prentice-Hall, 1972. p 160