[en] Barium hollandite and nickel-iron spinel have been irradiated with alpha particles emitted from a PuO₂ source in order to simulate the effects from alpha particles emitted in adjacent actinide-containing phases of the SYNROC assemblage. The unit cell of barium hollandite undergoes an apparent volume expansion of several percent and a weak transformation from a tetragonal to a monoclinic structure when irradiated with alpha particles to a fluence of 3 x 10²⁰ alphas/m² (approx. 0.05 dpa). The spinel structure, however, is very stable with respect to alpha irradiation and the irradiation-induced volume expansion of the unit cell is less than 0.2%. The results are compared with available neutron-irradiation data, and the differences in observed behavior discussed. 18 references