ORNL photo

At about a quarter past 10 on Saturday night, the High Flux Isotope Reactor achieved an amazing milestone — 1 million megawatt days of operation. It demonstrated the longevity and overall reliability of the world-class research reactor over the past half-century.

Think about this: The Oak Ridge National Laboratory reactor completed its first cycle of operations in June of 1966, and the HFIR continued to operate for more than 280 cycles at 100 megawatts power from 1966 until November of 1986. Because of embrittlement concerns regarding the pressure vessel and a lengthy review of the overall maintenance and oversight at the HFIR, the reactor was shut down for a few years in the late 1980s.

The power level was reduced to 85 megawatts when the reactor was restarted in January 1990, and it has been a workhorse ever since — with periodic time out for refurbishment, preventive maintenance and improvements, such as replacement of the beryllium reactor and installation of a Cold Source to enhance the experimental capabilities.

Overall, the reactor has operated for about 11,000 days. “This is impressive indeed!” lab reactor chief Tim Powers said via email.

The reactor is currently in its 465th cycle.

HFIR was restarted last week following an 18-day outage for refueling and maintenance. It was a short outage, but Powers said it was busy and productive.

The lab staff, among many other things, continued the installation of an “instrument air system” in the Guide Hall and continued work on seismic upgrades at the research reactor. There also was a long list of preventive maintenance activities, such as repairing lighting transfer switches and replacing a temperature conditioning system pump in the Cold Source (where one of four expansion engines was also replaced).

Workers also performed a number of calibrations and checks during the down time, including tests at the hydraulic “rabbit system” that’s used to shuttle radioactive materials.

The reactor is supposed to operate until March 18, when it will be brought down for a much longer maintenance period — 88 days — with some big-ticket items on the work agenda (including the replacement of 4 riser pipes in the secondary cooling tower).

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