Photos: A tour of Three Mile Island nuclear power plant

Steam wafts from the the cooling towers for the No. 1 reactor, with the inactive cooling tower from reactor 2 in the background at Three Mile Island near Middletown in this 2016 photo.

Richard Snyder, an armed security officer, in the generator room at Three Mile Island near Middletown Tuesday November 22, 2016.

The nameplate on the General Electric generator at Three Mile Island near Middletown Tuesday November 22, 2016.

After the Fukushima, Japan, nuclear power plant disaster of 2011, diesel generators were added at TMI to keep water pumping into the cooling system in the event of a total power failure. Tuesday Nov. 22, 2016.

Dave Williams, of Elizabethtown, is a shift manager at Three Mile Island near Middletown. When on duty, he is in charge of the plant's safe operation. Tuesday Nov. 22, 2016

Phones line outside the control room at Three Mile Island near Middletown Tuesday November 22, 2016. The dedicated phone lines provide direct access to govenment agencies.

Phones line outside the control room at Three Mile Island near Middletown Tuesday November 22, 2016. The dedicated phone lines provide direct access to govenment agencies.

Employees work in the control room at Three Mile Island near Middletown Tuesday November 22, 2016.

Power lines that provide enough power for 800,000 homes leaves the generator at Three Mile Island near Middletown Tuesday November 22, 2016.

Cooling towers for reactor 1 at Three Mile Island near Middletown Tuesday November 22, 2016.

Fire suppression system inside the turbine building at Three Mile Island near Middletown Tuesday November 22, 2016.

Reactor building for reactor 1. The concrete patch was part of a 2009 upgrade of the reactor. The building at right contains spent fuel at Three Mile Island near Middletown Tuesday November 22, 2016.

Concrete security barriers at Three Mile Island near Middletown Tuesday November 22, 2016.

The second cooling tower still has some parts dating back to 1974 including pieces of redwood at Three Mile Island near Middletown Tuesday November 22, 2016.

One of the cooling towers for reactor 1 got a $14 million renovation in 2009 at Three Mile Island near Middletown. This photo is from 2016.

Two water condensers at Three Mile Island near Middletown Tuesday November 22, 2016.

Condensate booster pumps inside turbine building at Three Mile Island near Middletown Tuesday November 22, 2016.

Cooling tower for the decommissioned reactor 2 at Three Mile Island near Middletown Tuesday November 22, 2016.