I've read that the normal US limit for nuclear workers is 50 mSv. The emergency limit for Fukushima Daiichi workers was raised to 250 mSv. Last I read, there were 21 workers there who had reached 100 mSv of cumulative exposure.

There are the two workers who had radioactive water spill into their low boots for almost an hour. The way I have seen it reported, they received about 175 mSv of gamma radiation, but 2-6 Sv of beta radiation to their feet and legs. Beta radiation is not so penetrating, but still, that is ionizing radiation, so that seems like a large dose to me.

However, it was also reported by TEPCO that there were not enough dosimeters in the early days of the crisis. Their supply of dosimeters had been destroyed or washed away somehow by the tsunami so some workers labored without them until they could get more. I remember reports of radiation spikes of 400 mSv/hour at the main gate in the those early days, so who knows exactly how much the workers were exposed to closer to the reactors back when things were really dire?