Abstract

On Aug. 25, 1965, the High Flux Isotope Reactor at ORNL began operating after only five years of construction. The 100-megawatt HFIR was championed by Nobel Laureate Glenn Seaborg, who recognized the need for a reliable source of transuranium elements. Nearly 60 years later, the water-cooled research reactor is more important than ever, supplying scientists with neutrons for conducting key research in materials science, nuclear fuels, biology, energy, environmental science, and forensics. The reactor is also a significant source of critical radioisotopes for the United States. 

The isotope production and neutron research at HFIR have led to many discoveries and practical applications, including new elements in the periodic table, life-saving medical advances, improvements in airport and dock security, and nuclear fuel for planetary and space exploration. 

Like any complex facility, HFIR requires routine maintenance, but because of its age, some of the more complicated major systems must be replaced in the coming decades. To accomplish these refurbishments, HFIR will be shut down for many months or longer at various times in the future. 

Some new parts of HFIR will include the permanent beryllium reflector (which will enable increasing annual production of plutonium-238 for NASA missions), a portion of the cold neutron source system (which will improve reliability, enabling increased annual operating time, and more research, including studying the behavior of proteins and polymers using lower-energy neutrons), and the pressure vessel (which contains the 85-megawatt reactor and the 16,000 gallons of water cooling it every minute).  

The shutdown to replace the reactor vessel will be the most significant outage of the reactor since it went critical. The new vessel will enable HFIR to operate past the turn of the century, making the reactor more than 135 years old! 

Biographical Sketch

Chris Bryan, leader of the Radioisotope Production Engineering and Analysis Section in the Radioisotope Science and Technology Division at ORNL, joined the lab’s Research Reactors Division in 2009 after nearly two decades leading development of medical and consumer products and industrial equipment. He began his ORNL career by leading a successful effort to increase the use of the reactor core for radioisotope production and materials and fuels testing. 

One week after arriving, Chris became involved in solving the problem of relieving the national shortage of molybdenum-99 (Moly-99), which is important because it decays to form technetium-99m; this radioisotope is the workhorse of nuclear medicine imaging because it helps doctors discover disorders in the brain, heart, and other human organs. For 10 years he led ORNL’s efforts supporting the National Nuclear Security Administration program to establish a domestic supply of Mo-99 without the use of highly enriched uranium.

A mechanical engineer with a B.S. degree from the University of Cincinnati and an M.S. degree from Ohio State University, Chris led the development and qualification of neptunium targets to help enable the eventual first production by HFIR of plutonium-238 in 2013. ORNL is the source of Pu-238 nuclear fuel needed to help power NASA’s future space probes; currently, the ORNL product is powering the Mars Rovers. 

In 2020, Chris participated in planning the replacement of the reactor pressure vessel, which will extend the operating life of HFIR well beyond the year 2100. He also led an internally funded project to conceive and plan new or enhanced HFIR facilities that could improve ORNL’s scientific capabilities during or following replacement of the pressure vessel.