Fission-fusion or accelerator-driven fission is pure BS. It combines the disadvantages of _both_ and none of the advantages.

Modern fission power plants are designed with a reactor vessel to last a century and to withstand high pressures and temperatures. It's built and emplaced permanently in a large concrete shielding structure.

In a hybrid design this just won't work. Fuel will need to be right next to a high-vacuum chamber that will need periodic maintenance.