Nothing wrong with saying broken.
Two other options though....
We could be technically precise to push the point-
"Sorry but ADIRS 1 is unserviceable which has rendered FMGC1 and one of the primary altimeters inoperative which is required for flight within RVSM airspace, forcing us to fly at a lower flight level. This will increase the engines rate of consumption of hyrdocarbons to a point where we will exhaust our variable and fixed reserves at approximately 25 miles to run to the initial approach fix."
Or speak in a language that would probably convince most people that returning to the terminal is a good thing-
"We could have a crack at it, but there is a much better chance that we would end up in a smoking hole."