PLYMOUTH, Mass. (AP) — Workers at the Pilgrim Nuclear Power Station are prepping for the plant’s shutdown after 47 years of operation.

On Friday, a team of workers will begin the process of reducing the plant’s power output from the current 40% of its capacity to zero. The process will occur over about a five-hour period in a 1970s-era control room that contains hundreds of levers, gauges, lights and buttons.

During a simulation on Tuesday, workers traded commands about which knobs to turn and buttons to press to safely shut down the reactor as alarms sounded and lights flashed.

Shutting down the reactor is the first step in a yearslong process of decommissioning the plant, removing spent fuel, and cleaning up the site.

The spent fuel rods will be stored in concrete casks.