The degraded polycube samples were tested in air and argon/oxygen atmospheres to determine the effect of size increase on the flammable gases concentrations. Within the size range tested, the flammable gas generation rate increases with increasing size but the extrapolation of the data to actual processing polycube size yielded flammable gas species concentration in the off-gas stream below the lower flammable limit of all the major gas species identified. Extreme surface area increase with a powder sample showed no significant effect on the flammable gas generation rate. The polycube went through the thermal stabilization process by undergoing both pyrolysis and oxidation generating at the end a plutonium oxide powder that showed unmeasurable weight change at 1273 K.