science

bombarding the isotopes with neutrons

There’s a word for that: a nuclear reactor!

You may be interested in: https://en.wikipedia.org/wiki/Breeder_reactor

A reactor whose main purpose is to destroy actinides rather than increasing fissile fuel-stocks is sometimes known as a burner reactor. Both breeding and burning depend on good neutron economy, and many designs can do either. Breeding designs surround the core by a breeding blanket of fertile material. Waste burners surround the core with non-fertile wastes to be destroyed. Some designs add neutron reflectors or absorbers.

Fusion power, if ever realized, also has a high neutron flux at a high neutron temperature, though it faces the same issue of “in the short term, it's more expensive than just storing waste in a hole”