From my understanding gamma rays can damage metal, making it brittle. Fortunaly, this appears to be little, but sill if you have a lot (like in p-D fusion) it becomes a serious hazard. The question is, how much? Specificly I need to know how much damange it does in compairison to Neutron radiation damage. For the sake of argument we asume the worse case scenario that all gamma radiation is absorbed, now how much will it weaken Metal compaired to high energenic neutrons (> 1 MVe).