October 2017

 

​By: Jens Odegaard

Tommy Holschuh earned his doctorate in nuclear engineering from the Oregon State School of Nuclear Science and Engineering in June 2017. In August, he, along with Abdalla Abou Jaoude from the Georgia Institute of Technology, was named one of two inaugural recipients of the Idaho National Laboratory's (INL) Deslonde de Boisblanc distinguished postdoctoral appointment. While at INL, Holschuh will be using a novel method he developed at Oregon State to support the modeling of its Transient Reactor Test (TREAT) Facility.

The namesake of the postdoctoral appointment, Deslonde de Boisblanc, was an early influential scientist at INL and designed the unique serpentine core of INL's Advanced Test Reactor. To honor his legacy, this appointment is "competitively awarded to early career researchers who embody the spirit of ingenuity of de Boisblanc and who have leadership potential."

A Nuclear Energy University Partnership Fellow during his doctoral studies at Oregon State, Holschuh developed a methodology and a detection system to quantify the Cherenkov radiation, or light, emitted by a reactor to determine reactor kinetics parameters. He calls it the Cherenkov Radiation Assay for Nuclear Kinetics (CRANK) system, which he describes in his dissertation. Holschuh used the Oregon State TRIGA Reactor for his research.

"The overall goal is that this might be used as an inspection tool by International Atomic Energy Agency (IAEA) inspectors," Holschuh said. "During an official inspection of a reactor facility under IAEA safeguards, the inspectors could utilize the CRANK system to measure a reactor pulse and be able to obtain information about that reactor to verify the facility's activities."

Holschuh's detection system fits in a briefcase-size hard case and consists of a photodiode connected to the end of a fiber optics cable, which connects to signal processing software. The photodiode is lowered into a reactor and measures the Cherenkov light. The software and components are off the shelf and altogether cost about $15,000. Other systems used by the IAEA for similar purposes cost $250,000 just for the cameras they utilize, according to Holschuh.

To interpret the data from the Cherenkov light and determine the reactor's parameters, Holschuh developed a mathematical formula to put into the software. "The most difficult part was determining how to interpret the pulses. Reactor pulses, or large power changes over a short period of time, are inherently different for every reactor. Every aspect of the reactor alters the shape of the pulse—the changing reactivity with temperature, the heat capacity of the reactor, the facility design," he said. "I was able to obtain a method that combined many of those aspects into a single variable that scaled between two unique reactor pulses."

This means that his method and system can be used for virtually any reactor that has the capability to perform a large power transient.

At INL, Holschuh will utilize this method for reactor safety rather than standard reactor safeguards. "As part of the deBoisblanc postdoctoral appointment, I will attempt to use that methodology and measure reactor pulses at the TREAT Facility," he said. Shut down since 1994, TREAT is in the process of being restarted—an effort involving Oregon State. It will be used to test nuclear fuel assemblies for power-generating reactors.

"The last time its reactor parameters were measured, experimentally, was in 1960," said Holschuh. "By obtaining more accurate experimental results for reactor kinetics parameters, it provides more representative values for the INL staff members who perform modeling and simulation for the TREAT facility. The pulse shape, and subsequent energy deposition into the fuel types being tested, are greatly influenced by the reactor kinetics parameters, so by knowing them more accurately you can more accurately determine the effects on the fuel being tested."

Holschuh completed two internships at INL during his graduate studies and will be working under the supervision of Dan Wachs, who earned his master's in both nuclear and mechanical engineering at Oregon State before earning his doctorate in mechanical engineering at the University of Idaho.

"We've been working with Tommy for several years and are looking forward to his return to INL," said Dr. David Chichester. Chichester is an INL directorate fellow and was Holschuh's graduate intern mentor at INL. "With key skills in reactor physics and radiation science, he's going to be making important contributions to our nuclear energy and nuclear nonproliferation research programs."