The Three Mile Island nuclear power plant in Middletown, Pa., site of the country’s worst nuclear accident, will close later this year.

The Three Mile Island nuclear power plant in Middletown, Pa., site of the country's worst nuclear accident, will close later this year.

The Three Mile Island nuclear power plant in Middletown, Pa., site of the country’s worst nuclear accident, will close later this year.

The Three Mile Island nuclear power plant in Middletown, Pa., site of the country’s worst nuclear accident, will close later this year.