# Beryllium Neutron Multiplier

We know that Beryllium is used in blankets of Fusion Systems because it is a neutron multiplier. I was wondering that if Beryllium is a neutron multiplier can it be used in the fission process(of nuclear reactors) to sustain a chain reaction?

• Using nndc.bnl.gov/exfor/endf00.jsp one can see that the (n,2n) reaction of Be-9 only kicks in above 1MeV neutron energy, and the cross section is less than 1 barn. Moderated fission reactors will not do anything unless the Be is part of the fuel, and even then the cross section isn't that great, needing a lot of Be. – Jon Custer Apr 3 '20 at 18:42
• Sort of related: physics.stackexchange.com/q/208690/123208 but it talks about using beryllium as a neutron reflector (and a moderator), not a neutron moderator. – PM 2Ring Apr 3 '20 at 19:08