To me they mean different things.
A "shutdown" is a planned or automated plant shutdown i.e. the processes are halted. This may be scheduled for maintenance, or in response to an automated sequence.
"We have a two week shutdown for maintenance in January."
An "outage" is an unplanned event where the plant shuts down in an unexpected manner or for an unexpected reason.
"Thousands of families suffered a power outage in the Florida are as a result of Hurricane IVAN."
I would iuse the term "shut-in" where all the workers (students) decide to shut themselves in i.e. occupy the premises, for a protest...
[/i]"Students in Manchester staged a shut-in today when they occupied University lecture rooms as a protest against cuts in education spending."[/i]
To me a down-turn is where the production is cut back or where the market is in recession.
"Thousands of steelworkers were laid of as a result of a downturn in the steel market."
...and...
"Unless there is a turnaround in fuel costs, many in the shipping industry will lose their jobs as companies struge to cut costs."
Others may understand some of these terms differently.
JMW
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