the military are the ones likely flying their helicopters. fire fighters are likely the ones using the apparatus for airport fires to shoot water because that was able to reach from a safer distance. the police riot water cannons couldn’t be used because they didn’t reach far enough without getting dangerous radiation doses.
in the plant would likely be experienced nuclear plant staff. they need to work using flashlights and be used to knowing how to deal with high radiation exposures.
i have heard they want retired plant workers to volunteer to go work in the plant. the thought is that they will die of some other cause before they die of cancer caused by this radiation if they keep the exposure times short. though i did see; “I don’t know any other way to say it, but this is like suicide fighters in a war,” said Keiichi Nakagawa, associate professor of the Department of Radiology at University of Tokyo Hospital.