A nozzle design and method for designing such a nozzle being adapted for three phase slurry flow from the choke into the flash tank during pressure let-down in autoclave mining operations that uses a selection of the expansion ratio in the choke to select a nozzle dispersion angle to select a spread of the flow over the slurry pool in the flash tank, to generally maximize the use of the pool for energy dissipation without causing undo wear and tear on the tank walls.