It was, and at no point during that incident was there any plausible risk of the core going prompt-critical or radioactive fuel being thrown into the atmosphere. As I remember it, the most serious risk was that the earthquake or tsunami could have damaged both the primary containment and the concrete "bathtub", so molten core materials could have leaked into the surrounding terrain. That's why they pumped in seawater to try to keep the core from melting down (an attempt which did not succeed).

As far as I know the primary containment for all Fukushima reactors is still intact.