In 2267, Corcoran and Burrows were members of a damage control team. When the number six warp reactor exploded without warning, the team entered the warp nacelle to fight fire and radiation. Burrows accidentally slipped into Corcoran, and hull metal tore open the crewman's environmental suit. He suffered third-degree burns on his left arm and absorbed a massive dose of radiation, which required more care than was possible in sickbay. Doctor Leonard McCoy requested that he be transferred immediately to a hospital.
Corcoran was treated at the penal colony on Certax. Doctors there gave him four weeks to live, but at least he was not in pain. Later, when escaped convicts created havoc aboard the Enterprise, Corcoran volunteered to sacrifice his life and save the ship by recovering debris scattered outside the ship that was too irradiated to handle safely. (TOS comic: "Prison Break")