© 2019 Elsevier B.V. Beryllium intermetallic compounds (beryllides) are well-known refractory and functional materials for fission and fusion applications, specifically as reflectors and multipliers. For advanced neutron multipliers, our research group has investigated many kinds of beryllides. Due to its nuclear properties, single phase Be 13 Zr beryllide was selected and successfully fabricated via plasma sintering of the homogenized Be 13 Zr powder. Its reactivity against 15% H 2 O was evaluated, and unexpected catastrophic oxidation (pest reaction) occurred at a low temperature range, from 973 to 1123 K, leading to the disintegration into a powder. This is caused by the intergranular degradation on the boundaries between the oxide layer and the matrix, as well as the continuous oxidation through cracks that arise from stress generation on the oxides. However, this pest reaction was suppressed by Si doping. Si likely relieves the stress near the grain boundary and in the oxide layer. The Si-doped Be 13 Zr had the lowest hydrogen generation rate among the evaluated samples at 1273 and 1473 K, which is also much lower by approximately two or three orders of magnitude than that of Be at 1273 K.