Naomi Senehi: How did you enter the nuclear space?

Michael Reichenberger: Michael Reichenberger grew up in Kansas, where nuclear provides a significant amount of power to the grid, but was unaware of the impact of nuclear energy on his community. Reichenberger was drawn to study mechanical engineering at Kansas State University and fell in love with nuclear when he was required to take an introduction to nuclear engineering course. He spent all of his electives in the nuclear program and stayed at the university to pursue graduate studies focused on radiation detection, specifically micro-pocket fission detectors. Reichenberger was attracted to nuclear engineering due to its base in the logical sequence of physics. Nuclear engineers usually have a deliverable to apply the physics to, while nuclear physicists are more interested in understanding what is happening and why.

Q2

Naomi Senehi: What is a micro-pocket fission detector?

Michael Reichenberger: Michael Reichenberger’s graduate dissertation focused on micro-pocket fission detectors (MPFD’s), which are fission chambers that detect neutrons. A converter material that fissions, such as uranium, absorbs a neutron and splits into two parts which have a lot of energy. These parts go in two different directions and the energetic fission fragments creates ionization as it passes through a gas. This can be measured by applying an electric bias across the gas. MPFD’s are special because they can be put inside the core of a nuclear reactor without affecting the rest of the reactor. The smallest MPFD Reichenberger made had a chamber that was a third of a millimeter in diameter and was designed to go inside a flux wire cord in a test reactor in New York. It was challenging to push the wires inside the tube, so Reichenberger had the idea to braid the six wires together, which stiffened them successfully.

Q3

Naomi Senehi: What was the main premise of your PhD program and what did you uncover?

Michael Reichenberger: The title of Michael Reichenerger’s PhD dissertation was “The Design, Development, and Deployment of the Micro-Pocket Fission Detector”. The design phase goes back to basic physics to design the system to conduct a measurement. The development phase looks at how to actually build the detector using and sourcing materials that could be used at a nuclear reactor. The deployment phase involves putting the MPFD in the Trigger Reactor at Kansas State University and took real-time measurements at different axial locations in the reactor and during pulses. A nuclear reactor pulse is when the control rod is pneumatically ejected, allowing the reactor to go prompt supercritical and increase power exponentially. As reactor power increases, the temperature of the fuel increases and its strong negative temperature coefficient drives the temperature down, bringing the power down with it. Since this spike happens in a matter of milliseconds, most conventional tracking methods were not adequate to measure the neutrons.

Q4

Naomi Senehi: What advice would you give to students pursuing a PhD in the nuclear space?

Michael Reichenberger: Michael Reichenberger credited involvement in non-research activities and programs in helping him be successful in graduate school, by allowing him to network outside his core group and giving him another outlet. However, Reichenberger also recognized the power of saying “No” in order to identify your priorities and focus on the research when needed. Reichenberger now works at the Idaho National Laboratory as the Technical Lead. The Advanced Test Reactor (ATR) is the premiere irradiation facility for nuclear fuels and materials testing in the world which can sustain long cycles and high flux levels with large irradiation ports. The ATR has 45 different irradiation ports and nine different locations that can simultaneously be at different flux levels. The Radiations Metrics Laboratory (RML) supports ATR by conducting routine gamma spectroscopy measurement, measuring stack gas, and checking samples for unexpected activation. The RML also deploys and measures the radiation dosimeters that go into the core. Dosimeters are deployed throughout the core with cobalt and nickel wires, which become radioactive; after the cycle, the radioactivity of the wires are measure to determine how many neutrons they were exposed to.

Q5

Naomi Senehi: How can you use what you studied in your nuclear PhD in your role at Idaho National Lab?

Michael Reichenberger: Michael Reichenberger works at the Idaho National Laboratory (INL) as the Technical Lead. The value of real-time sensors is maximized in test reactors that have lots of power fluctuations, instead of commercial plants which have a steadier power output. However, the research and data collected at the test reactors translate directly into improvements for the commercial industry because research can move quickly. The current development cycle for a new fuel is 20 years due to testing and validation that must be completed to qualify the fuel, so there is ample room for improvement. Thermocouples have a large overhead to deploy in a test reactor so they are not always included in experiments. If there is an opportunity to unify the system and measurement by internalizing it to the unit, it could take some of the project-specific engineering for thermocouple deployment. The Advanced Gas Reactor at INL completed an experiment in which a gas lead was piped out into a measurement bay that goes to where the fuel is being irradiated. If there is a fuel failure, the fission product gases can be monitored. Innovation on how sensors are used can improve the data collected and used for commercial development.

Q6

Naomi Senehi: What are some of the new instrument types coming from the lab to be used commercially?

Michael Reichenberger: Since there is not much new nuclear construction in the U.S. at this time, Michael Reichenberger’s current instrumentation research is not ready to be commercialized yet. Sensors used in research reactors are more technically complicated and are innovative in the way commercial reactors are designed and build. However, these same sensors are not necessarily incorporated and used in commercial reactors. Data from research reactor sensors are used in commercial development, but commercial reactors primarily use sensors for operation and service. Having an integrated neutron sensor incorporated into the fuel levels could potentially provide burnup calculations, which may allow the current fleet to have longer fuel cycles or more efficient fuel usage. Instrumentation will be essential for the operation of advanced reactor designs, such as molten salt reactors, since there are currently no standard methods to conduct neutron methods in these environments. The nuclear industry will be sustained by maintaining the current fleet, which can be achieved by developing new fuels, and by developing reactor technologies. Idaho National Lab has a unified mission which empowers the team to work together and value each member of the team.

Q7

Naomi Senehi: What do you hope for the future of nuclear?

Michael Reichenberger: Michael Reichenberger is encouraged by continued development of integrated energy systems and people’s understanding the nuclear energy needs to be a part of the grid. Nuclear is essential to climate change. Reichenberger advocates for maintaining and extending the life of the current fleet of nuclear reactors, even as the next generation of technology is in development. The nuclear industry is very young, but people in the field have a vision for what is possible with nuclear energy.

7-10 Bullets
- Michael Reichenberger’s entrance into the nuclear industry as a mechanical engineer - How fission detectors measure neutrons in nuclear reactors - Reichenberger’s design, development, and deployment of Micro-Pocket Fission Detectors in a test reactor - The impact on nuclear reactor power and temperature when it goes prompt supercritical - Advantages of the Advanced Test Reactor for nuclear fuels and materials testing - How the Radiations Metrics Laboratory supports the Idaho National Lab by measuring irradiation - Benefits of real-time sensors in test reactors and how they impact development of commercial reactors - Potential value of real-time sensors in the operation of advanced reactor designs.