IIUC, only the De-De reaction generates neutrons. This is the process they use for generating He-3 (and a tiny bit of power). The video mentions that their plan

IIUC, only the De-De reaction generates neutrons. This is the process they use for generating He-3 (and a tiny bit of power). The video mentions that their plan is to separate the De-De reactors from the from the power-generating De-He3 reactors (which do not create neutrons). Therefore, their main power-generating reactor won't have to deal with damage from neutrons.