[en] Results of initial tests on transuranic migration into commercial refractories are reported. Five castable refractories and a plastic-bonded refractory were tested using the cup test method. Initial results indicate that castable materials will not survive conditions expected in the slagging pyrolysis unit; plastic refractories appear to have better performance. The major mechanism of migration into the tested refractories is pore penetration. Al₂O₃ and Al₂O₃-Cr₂O₃ phases appear resistant to chemical diffusion of transuranics. 2 figures, 16 tables