On one hand, 100 TBq is less than a thousands of a gram of Ruthenium 106. On the other hand, anybody handling radioactive samples with terabecquerel activity wi

On one hand, 100 TBq is less than a thousands of a gram of Ruthenium 106. On the other hand, anybody handling radioactive samples with terabecquerel activity will be very very aware that they are handling a lot of radioactivity. So my guess is, either an accident or an breach of safety protocols at a nuclear facility. Either way, the source is most likely aware that something did go wrong.