At 12:07 P.M., E.D.T. today, forty-five years and eighteen days after being commissioned into commercial service on September 2, 1974, the Three Mile Island Nuclear Generating Station’s Unit 1 reactor was shut down for the final time. There will be no refueling. There will be no more electricity furnished to the grid by the plant. It is henceforth a user, not a producer, of energy.
Here’s the final shutdown, in pictures…
Work began to build the Three Mile Island Nuclear Generating Station in 1968. In this photo taken on July 7, 1970, one can see that Unit One’s reactor containment building and cooling towers have been erected and that the excavation and early construction of the ill-fated Unit 2 is underway. (United States Department of Agriculture Agricultural Stabilization and Conservation Service image)
11:15 A.M., E.D.T. Water vapor clouds rise from the Unit 1 cooling towers (left) during the plant’s final hour of electricity generation. Smoke in the center of the photo is from a diesel-powered auxiliary steam generator that is used during the shutdown process.
11:40 A.M., E.D.T. Three Mile Island Unit 2 (left), and Unit 1 (right), just prior to the latter’s final shutdown. Unit 2 is presently in monitored storage. It has not operated since the 1979 accident. Unit 1 did not operate for 6 years following Unit Two’s shutdown. Since being permitted to restart, Unit 1 has continued to be a reliable pressurized water reactor electricity generating system.
12:00 Noon Unit 1 in the process of shutdown. Control rods were inserted into the fuel assembly and “zero percent” generation was marked at about 12:07 P.M., E.D.T. By then, the heat release rate in the core had dropped to 10% of the level produced while a full-capacity reaction is occurring.
Just after the reactor was placed in cooling mode, a press conference got underway at the Three Mile Island Training Center, site of all the press action during 1979’s Unit 2 accident. Dauphin County Commissioner Mike Pries lamented the eventual loss of 675 full-time jobs at the T.M.I. facility. He noted that if the plant were not now closing, 1,000 workers would be arriving to refuel and service the reactor. The local economy will now miss out on the 36,000 “room nights” of revenue previously generated by skilled labor remaining in the area for a little more than a month to complete a shutdown refueling.
Dave Marcheskie, Exelon’s Senior Site Communications Manager at Three Mile Island, reported that by shutdown, Unit 1 had completed a record 709 continuous days of safe and reliable energy production. Despite being permitted through 2034, in 2017, Exelon Corporation announced plans to shut down the T.M.I. Unit 1 reactor early, citing an inability to operate the facility profitably while competing with natural gas-fired generators and subsidized producers including wind turbines.
It’s always lots of fun at a Three Mile Island news conference when there’s a dissenting point of view. I’ll bet Uncle Tyler Dyer knows this guy, although he’s probably upset with him for not wearing one of the custom shirts he makes. Better luck next time Uncle Ty.
12:59 P.M., E.D.T. Nearly one hour after shutdown, steam clouds continue to rise from the Unit 1 cooling towers. One thousand gallons per minute or more of water are circulating through the primary (reactor) cooling loop to absorb the energy produced by the “leftover” fission products that are decaying in the core.
1:23 P.M., E.D.T. The last remaining heat from the core is transmitted by a primary cooling loop inside the reactor containment building to a secondary loop that would, when making electricity, drive the steam generator in the neighboring building. A third loop, which never enters the reactor, cools the condenser on the secondary loop, and finally surrenders its heat in the cooling towers. Unit 1 can use “once-through” river water to direct cool the condenser during shutdown.
2:11 P.M., E.D.T. The cooling process progresses.
2:29 P.M., E.D.T. Wispy water vapor clouds are gradually diminishing in density at the top of the Unit 1 cooling towers (right).
2:29 P.M., E.D.T. Yes, that is a water skier behind the boat.
2:33 P.M., E.D.T. The periods of time without visible steam clouds lengthen as the heat release rate from the reactor core continues to plummet toward a cold shutdown.
Environmental monitoring will continue on and around Three Mile Island during the decades of cleanup and decommissioning to come.
By 2074, as the centennial anniversary of Unit One’s commissioning comes around, the cooling towers and most of the other buildings at T.M.I. should be gone. By then, Three Mile Island may look more like it did during the years before construction ever began. By then, nothing but a historical marker will be left to tell future generations of the events that transpired during the power plant’s operating years. Here’s an idea for a sign to go with it: “Three Mile Island N.W.R. (Nuclear Wildlife Refuge), people keep out!” By 2074, maybe society will have enough sense not to build and live on beaches, in tidal estuaries, and in floodplains. Wouldn’t that be nice? (United States Department of Agriculture Commodity Stabilization Service image-November, 1956)