Kelley Beierschmitt, director of nuclear operations at Oak Ridge National Laboratory, said the problem was not in a safety-related system. However, the electrical line did affect systems that control motor operations and maintain consistent power levels at the 85-megawatt research reactor, he said.
The problem was detected at about 9 p.m. June 21 when control room operators got a warning light indicating a relay failure, Beierschmitt said. A subsequent series of checks confirmed the problem, he said.
The electrical line was replaced over the weekend, and restart testing was being done today, Beierschmitt said. Lab officials have restarted the research reactor, he said.
Beierschmitt said the electrical line was at least 20 years old, and that probably was the reason for the failure. The laboratory is gradually replacing old parts and systems at the research reactor, which was built in the 1960s.
The unplanned shutdown occurred six days before the reactor's regular outage for refueling and maintenance, Beierschmitt said. So the plan is to operate it for the rest of this week to complete the regular fuel cycle and then take it down again for refueling, he said.
The problem shouldn't affect the reactor's rest-of-the-year schedule for research and isotope production, he said.