Robots, especially when they are fitted with transistors, printed circuits and micro processors, are extremely vulnerable to radiation.
There was a reason why the Mig-29 partially used vacuum tubes for basic flight systems in case of an electromagnetic impulse, or radiation.
Two robots have been tried, and they stopped a hundred meters from the plant or so they said due to circuit failures.
Certainly, there are also special radiation suits made in the US that have been sent to Japan, but they never used them, i am sure the workers were never shown them at all. Plastic bags are so much better.
As well i saw at at least one photo the workers did not wear their oxygen masks right - it's all about "saving faces"
Greetings,
Catfish