BS, I suspect. Realistically, the pellets end up critical, not supercritical. They then slowly heat up, expand, and fall apart over the course of a few hours or days.
That would happen if it was acutally fissionable Pu-239 instead of Pu-238
Hoagland is nuts
Hoagland served as a "Curator of Astronomy & Space Science" [3] at the "Springfield Museum of Science