ORNL reactor recovers from unplanned weekend shutdown; part replaced in auxiliary control room

hfirA view of the High Flux Isotope Reactor’s core at Oak Ridge National Laboratory. (ORNL photo/Jason Richards)

Workers manually shut down Oak Ridge National Laboratory’s High Flux isotope Reactor over the weekend after the reactor’s control system generated a signal for an automatic reduction in power. A faulty part was identified and replaced by workers, and the 85-megawatt research reactor reportedly returned to full power late Monday afternoon.

According to information provided by Paul Langan, ORNL’s associate lab director for neutron sciences, the reactor and associated systems were placed in a “safe shutdown condition” around noon Saturday, using normal operating procedures.

“Discussions with the operating crew indicated that the plant was in a stable condition and plant parameters were not changing prior to the event,” Langan said via email. “Investigation into the cause identified an internal fault in a recorder in the auxiliary control room as the most likely cause. The recorder was replaced with a calibrated spare, and the post-maintenance testing was completed satisfactorily.”

The normal operating cycle was resumed Monday evening after Johnny Moore, the Department of Energy’s site manager at ORNL, gave his approval,  Langan said.

The ORNL official said there were 27 experimental scheduled to run during the shutdown period over the weekend. Those involved 38 researchers, and Langan said they would be given priority beam time at the reactor to complete their work and, if necessary, will be rescheduled in later operating cycles at HFIR.

Langan praised the reactor staff for their hard work and dedication over the weekend to address the problem and to get the reactor — one of ORNL’s key research facilities — back in operation as soon as possible.

The High Flux Isotope Reactor was still early in its fuel cycle when the issue occurred. The reactor was restarted last week following an 80-day outage — the year’s longest down time — for maintenance and upgrades.

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About Frank Munger

Senior Writer Frank Munger covers the Dept. of Energy's Oak Ridge facilities and many related topics — nuclear weapons, nuclear waste and other things nuclear, environmental cleanup and science of all sorts. Atomic City Underground is, first and foremost, a news blog, but there's room for analysis, opinion and random thoughts that have no place else to go.