Fun fact: the police found a "3d printed, bomb shaped object" and put it into an evidence bag with the label "offence: causing an explosive blast". The object can be seen in action here:
But the criminal offence is spot on: http://cdn1.spiegel.de/images/image-1310464-860_poster_16x9-...
Amusingly enough, they labeled it "mutmaßliches Modell einer Atombombe" (presumptive model of an atomic bomb) with the crime being "Herbeiführen einer Sprengstoffexplosion" (causing an explosion), but the relevant norm [1] explicitly excludes nuclear explosions.