OREGON STATE UNIVERSITY

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1.1 MW TRIGA Mark II Pulsing Research Reactor

The Oregon State TRIGA Reactor (OSTR) is a water-cooled research reactor which uses low-enriched uranium/zirconium-hydride fuel elements in a circular grid array. TRIGA stands for Training, Research, Isotopes, General Atomics. The reactor is used for training students, various research projects and isotope production. The reactor has a variety of irradiation facilities available. OSU is one of the few educational institutions in the United States with a TRIGA research reactor and is one of only two nuclear reactors in the state of Oregon (the other being a 250 kW reactor at Reed College). The reactor is housed in the OSU Radiation Center.

The reactor is licensed by the U.S. Nuclear Regulatory Commission to operate at a maximum steady state power of 1.1 Megawatts (MW). The OSTR is also a pulsing reactor. It is equipped with a pneumatic transient rod which can eject from the core, causing a prompt reactivity insertion and a rapid peak power rise. The OSTR is licensed for a maximum pulse reactivity insertion of $2.30, which is approximately a peak power of 3000 MW.  Below are two videos demonstrating the OSTR's pulsing capability. The first video shows two pulses, worth $1.40 and $2.00 respectively. This video shows pulses in real-time, then at slowed speeds to demonstrate how rapid the events are (on the order of milliseconds). The pulses are initiated at an initial reactor power of 15 watts. The $1.40 pulse has a peak power of 167 MW and the $2.00 pulse has a peak power of 1500 MW. 

The second video was recorded using an iPhone 6 in "slo-mo" mode. This HD video was recorded at 240 Hz to further demonstrate the speed and safety of a pulsing event. As the video begins, the transient rod is ejected; notice that the connecting bolts on the rod begin to raise. As the rod is ejected, the pulse begins with a burst of Cerenkov radiation (the blue glow). Note that the pulse begins and ends without any operator action. You can see the other control rods' connecting bolts do not move until after the flash. This means that the reactor shuts itself down before the control rods begin to insert. The TRIGA reactor is able to do so based on its design and the design of the zirconium-hydride fuel, which has a prompt negative temperature coefficient. As the fuel heats up, it inherently shuts the nuclear reaction down. This pulse was a $1.50 insertion, which equates to approximately 350 MW.