By developing radiation-hardened electronics that can operate reliably within a near core environment, the safety and operational efficiency of plants can be improved through early signal pre-amplification, analog signal processing, and analog to digital conversion. Wide bandgap semiconductors offer a potential solution to this issue, offering greater voltage breakdowns, higher current limitations, and faster switching speeds compared to traditional silicon devices. Gallium Nitride (GaN) transistors can provide reliable, safe communication and monitoring capabilities to these high-temperature, high radiation environments of advanced reactors.



This project focuses on testing samples of GaN transistors at the Ohio State University National Reactor Laboratory (OSU-NRL).These transistors will comprise of both E-mode and D-mode as well as analog and digital cells for wireless sensor communication devices. Experiments will beneeded to confirm the ability of the devices to function in environments with high temperature (>400°C), total ionizing dose (TID) (>100 Mrad (GaN)), and neutron fluence (~10^16 n/(cm^2 )).



The first round of testing will see the samples irradiated using a Co-60 gamma source delivered over 1000 hours to provide a total TID (Total Ionizing Dose) of 12 Mrad. OSU-NRL presents the capability for easy in-situ measurement for live monitoring of electrical properties. OSU-NRL also offers another unique capability, the ability to perform irradiations in external large dry tubes. These dry tubes are right next to the core and are available with an inner diameter of 6.5-in or 9.5-in providing a neutron flux up to 10^11 n/(cm^2 s). The second part of the testing will put the GaN samples under neutron irradiation with thetotal fluence obtained by the sample at about 10^(16 ) n/(cm^2 ). The in-situ capability of OSU-NRL will offer the unique opportunity to monitor the performance of the devices under the increasing doses as opposed to the usual “cook-and-look" approach offered by most studies with only post-irradiation characteristics. The lead wires for the in-situ testing will be calibrated with a control group to record the base line noise level induced between wires and connections. The third round of testing will focus on a gamma-neutron mixed irradiation with simultaneous heating to test the performance of the devices undergoing dynamic annealing from the high temperatures. The team will heat the devices up to 400℃ while achieving a combined gamma-neutron dose.



For the first irradiation, the team will measure and characterize the current-voltage (I-V) characteristics of the AlGaN/GaN HEMTs during and after irradiation. This will be performed using at least 2 source-meter units (SMUs) that will be switched between more than 16 selected AlGaN/GaN HEMT devices during irradiation. After irradiation, we will perform PIE using either SMUs or semiconductor parameter analyzers to characterize the devices’ electrical performance more accurately and precisely. These electrical characterizations will be use to develop circuit models for the devices which include the effects of radiation degradation to verify and improve existing SPICE models for electronics developed by DOE NE programs.

The use of in-core or near-core sensor, instrumentation, and control systems involves the placement of a detector at the desired measurement location within or near the core of a nuclear reactor with long cabling run out of containment for interfacing. The result is not only multiple penetrations into reactor containment, but electronically noisy signals complicating the already difficult task of reactor monitoring instrumentation and control (I&C). Wireless sensor communication link provides a potential solution for minimum cabling free of wall penetration.

State-of-the-art radiation-hardened (rad-hard) electronics are a critical limitation for nuclear instrumentation. Research and development into rad-hard electronics and electronic materials technologies is essential to enable safer operation with improved monitoring and control of the existing nuclear reactor fleet and next generation reactors. Modern reactor instrumentation and control systems rely on the placement of a small signal detector at the desired measurement location in or near thereactor core. These small signals must traverse lengthy cables that penetrate containment and are routed over hundreds of meters to a room-temperature, low-radiation environment where the sensitive acquisition electronics operate. Without active electronics, the electronically noisy signals cannot be multiplexed efficiently and require multiple penetrations that degrade the containment integrity. Signal accuracy, precision, and fidelity are improved by reducing the length of the electromagnetic noise susceptible cabling between the instrument and associated electronics. Deploying rad-hard electronics capable of operating within the high-radiation and high-temperature environment of an operating reactor core would increase the fidelity of measurements through early signal pre-amplification, analogsignal processing, and analog-to-digital conversion.



While Si-based electronics have successfully been irradiated to beyond 100 Mrad, the temperature limitations of these components rarely exceed 150-225°C. Semiconductor circuits based on the wide bandgap material GaN are becoming prominent in power electronics andradio frequency applications due to their higher temperature limitations (>500°C) and fast switching speeds. Wide bandgap semiconductors such as GaN and SiC have been shown to have incredible radiation tolerance (>100 Mrad; 10^16 n/cm2), making them a prime candidate for surviving the harsh radiation and temperature environments associated with existing and next generation reactors. This proposal seeks to irradiate single transistor elements and rudimentary semiconductor logicstandard cells intended as the building blocks for sensor digitization and wireless communication. Through the irradiation of these circuit components, high-radiationand high-temperature electronics can be designed to support instrumentation and control of reactors while reducing the cabling footprint. This is the first time that Gallium-Nitride HEMTs developed for rad-hard reactor instrumentation and control circuitry under the NEET competitively awarded project 21-24446 will be irradiated in a gamma and mixed gamma-neutron irradiation.