It said in the article, they had a lot of difficulty finding a foundry that would actually let them do it.

> None of the metal foundries we contacted in the US and Mexico would let us jump a robot with lithium-ion batteries into their expensive equipment. We even reached out to former MythBusters to help with the search. In the end, the only place in the world we could find willing to take this on was a foundry in Imatra, Finland.

Those explosions are in the video. They seem to be using slow motion so you can see the detail of the explosions.