Exelon said that it plans to close the 29-year-old Clinton plant "due to deteriorating economics" by June 1, 2017. CLINTON — Exelon Corp. has formally notified the Nuclear Regulatory Commission that it has decided to close the Clinton and Quad Cities nuclear stations in 2017 and 2018, respectively. In its "Certification of Permanent Cessation" letter sent to the NRC, Exelon said that it plans to close the 29-year-old Clinton plant "due to deteriorating economics" by June 1, 2017. read more