8 8th's Blue
The closest rwy to DN that is long and wide enough for a 146 is Bathurst Island @ 43nm. However it's PCN is 8 with an 84psi tyre limit and the aircraft has an ACN in the region of 20ish with 165psi tyres.
So in an emergency, sure one can land but the paper work will be a killer as will tea and bikkies @ HO.
The closest suitable aerodrome to Darwin is Tindal. 154nm about 1250 kg fuel burn. Fixed reserve for a 300 series 146 is 950 kg.
Relying on FR for "these extremely rare unplanned for situations, to be used as a last resort" might work in light aircraft, or on the east coast where generally suitable aerodromes are in abundance but it doesn't work in heavier aircraft or remote Orstaylya.