Startup neutron source strength evaluation of Three Mile Island Unit 1 after extended shutdown

Three Mile Island Unit 1 (TMI-1) was shut down February 17, 1979, for refueling and went critical October 3, 1985 (2420 days later), without inserting any external neutron sources. The intrinsic neutron source strength was evaluated and confirmed in 1981 through analyses and supporting subcritical tests. Results showed TMI-1 could have performed a successful startup at least through 1990 without discrete neutron sources.