I just read that a second exploratory robot sent into the #2 unit’s primary containment vessel had to be abandoned after losing mobility(unknown if it was radiation or just tread crud; but they had to cut the tether and leave it).
A prior attempt with(I think) the same model robot had to be aborted early after the cameras started failing more rapidly than expected.
So far, so not good; but not terribly surprising. I looked up Toshiba’s press piece for these robots; and then I became confused. They are supposed to be good for a dose of 1000 sieverts during the course of an operation; but everything I read about sieverts tells me that those are the units for ‘equivalent dose’ or ‘effective dose’; both of which are based on weightings of relative biological effectiveness of different sorts of radiation; and weightings of the risks of exposure to different parts of the human body.
I can quite readily understand how an analogous metric for a given robot would be useful; and quite possible to develop; but I don’t understand what it means to quote a robot’s expected survivable dose in sieverts.
Are they saying that it is expected to survive radiation levels that would produce a 1000 sievert exposure in an equivalently placed human? Are the biological effectiveness weightings for tissue sufficiently similar to those for hardware that it is considered negligible for stating an absorbed dose?
I can see why just just the absorbed dose in grays wouldn’t be enough to be meaningful for a robot(just as it isn’t for humans, which is why sieverts are a thing); but what does it mean when a unit developed for human exposure modeling shows up without further comment on a robot’s spec sheet?