The energy amplifier is a subcritical nuclear power reactor.
Subcritical reactors cannot sustain a nuclear chain reaction without external help. Concepts show that a subcritical reactor can be made critical by high energy protons inserted by a nuclear accelerator. If the accelerator is shut down or fails the reactor will stop fission reactions within fractions of a second.
If the reactor has a large volume to dissipate the heat produced by the decay of fission products it can be designed fail save. The energy amplifier avoids catastrophic failure of a nuclear reactor setup very effectively.
It is also adaptable to different nuclear fuels promising easier to handle nuclear waste or the use of plutonium from military applications and destroy it during energetic use.