This is a 20 MW test reactor. Most power reactors run 650 to 1200 MW, so the core contains very roughly 1/50th the nuclear material of a power reactor. it’s in a pool, a configuration with which I am familiar and have first hand experience, but I am not familiar with a “tank-pool” configuration.
This was a trained team, with a rehearsed plan for entry, a plan that worked.
It is clear the team knew what to expect, which indicates familiarity with the plant, quite possibly inside knowlege, even possibly inside assistance.
This may very well be connected with an succesful assassination attempt.
This trained team got within feet of their objective, the control panel, though we don’t know what their plan was.
First guess, Al Qaeda.
Second guess, enviro-terrorists, like Greenpeace.
Head’s up, people, whatever was attempted here is of grave concern to the entire planet.
Taking operational control of a nuke facility would cause worldwide angst.