Search

Many studies are undertaken into nuclear power plants (NPPs) in preparation for accidents exceeding design standards. In this paper, we analyze the applicability of various wireless communication technologies as accident countermeasures in different NPP environments. In particular, a commercial wireless communication module (WCM) is investigated by measuring leakage current and packet error rate (PER), which vary depending on the intensity of incident radiation on the module, by testing at a Co-60 gamma-ray irradiation facility. The experimental results show that the WCMs continued to operate after total doses of 940 and 1097 Gy, with PERs of 3.6% and 0.8%, when exposed to irradiation dose rates of 185 and 486 Gy/h, respectively. In short, the lower irradiation dose rate decreased the performance of WCMs more than the higher dose rate. In experiments comparing the two communication protocols of request/response and one-way, the WCMs survived up to 997 and 1177 Gy, with PERs of 2% and 0%, respectively. Since the request/response protocol uses both the transmitter and the receiver, while the one-way protocol uses only the transmitter, then the electronic system on the side of the receiver is more vulnerable to radiation effects. From our experiments, the tested module is expected to be used for design-based accidents (DBAs) of “Category A″ type, and has confirmed the possibility of using wireless communication systems in NPPs.

We investigated the scintillation properties of Ce:GPS (Ce:Gd2Si2O7), Pr:LuAG (Pr:Lu3Al5O12), and LYSO (Lu2(1 − x)Y2xSiO5) scintillators in high-temperature and high-radiation environments to evaluate their potential application in harsh environments. The temperature dependence of the scintillators was investigated from room temperature to 350 °C. The LYSO scintillator was very vulnerable to high temperatures while the light output of Pr:LuAG scintillator decreased rapidly above 200 °C. The Ce:GPS scintillator demonstrated almost constant light output to 250 °C and decrease about 30% at 300 °C. We also measured the changes in the light yield and transmittance of the scintillators in the range of 0–3.83 MGy. At the highest gamma rays radiation dose, the light output of Ce:GPS, Pr:LuAG, and LYSO compared to the reference scintillator were 15.3% ± 1.8%, 36.7% ± 3.1%, and 73.4% ± 2.6%, respectively. However, Ce:GPS demonstrated a pronounced and fast recovery via thermal annealing, and it recovered within 30 minutes at 400 °C and 1 hour at 300 °C. These properties permit the potential application of Ce:GPS in extreme environments.

This work experimentally compares total ionizing dose (TID) effects on various inverter designs, which are fundamental components for implementing radiation hardening by design (RHBD) digital circuits. Based on prior works, which reported that leakage current variation of NMOS transistors is significantly larger than that of PMOS, this work suggests design methodologies to alleviate TID effects on NMOS transistors with the following inverter topologies: stacked NMOS inverter, pseudo PMOS inverter, PMOS-only inverter, and dummy transistor inverter. We have also investigated different sizes of the inverters as well as different PN ratios to optimize them for a more robust design that can operate under high radiation environments. These designs are fabricated in the 180 nm CMOS process and measured performance degradations by using a 60Co source. Experimental results show that the stacked NMOS inverter provides best performance in terms of switching point variation, area, and power consumption. In addition, one with larger transistor size and PN ratio is more helpful in TID hardening. Given that an inverter is an essential and basic building block of digital systems, the proposed techniques can be adopted in any systems requiring operation under radiation-emitting circumstances, e.g., measurement devices in nuclear power plants or electronics in space.

This paper presents a neural network approach for the identification of gamma emitting radionuclides measured by Silicon Photomultipliers (SiPMs). SiPMs have wide-ranging applications in the field of radiation monitoring and medical imaging due to their high quantum efficiency, high gain, and compactness. For better accuracy on the measured information, however, we should consider the disadvantages: dark count rate, optical crosstalk, and temperature sensitivity. Regarding temperature dependencies, conventional approaches are mainly focused on compensating gain variances against temperature by adding circuits or calibrating signals. In contrast with previous works, we propose a new approach exploiting two-layer fully connected neural network with a SiPM. The neural network is composed of rectified linear unit (ReLU) layers and a softmax layer. A Saint-Gobain Lutetium-yttrium oxyorthosilicate (LYSO) and a SensL MicroFJ SiPM combined with a charge sensitive amplifier (CSA) circuit were used in the data acquisition to detect 137Cs and 152 Eu. The decreasing logistic regression cost function shows that the proposed neural network converges to a global minimum, verifying the possibility of distinguishing Cesium from Europium in the mixed radioactive environment.

This work presents a detector capacitance compensation circuit for array-type SiPM-based radiation detectors while maintaining high-quality pulse information, including energy and time resolution. The major component of the proposed configuration, a unity-gain amplifier exploiting the Miller effect, maintains the same AC voltages on two sides of a detector, resulting in no effective detector capacitance between the nodes. This technique ideally allows combining channels without performance degradation in terms of rise time and amplitude of signals that can be caused due to the accumulated capacitance when SiPM cells are shorted in parallel in a signal multiplexing scheme. In order to verify the configuration, we designed and built a test board inserting a unity-gain amplifier between a 16-pixel SiPM array and a conventional charge-sensitive amplifier as a preamplifier . The measured pulses at the output of the front-end system show that the detector compensation technique can successfully mitigate performance degradation of rise time and amplitude as well as coincidence time. This technique can be adopted in many applications that require a multiplexed readout of a large number of array-type detectors, e.g., in cargo scanning technologies, radiation monitoring in nuclear plant facilities, and advanced medical imaging instruments such as PET and SPECT.

This paper describes an integrated circuit design for a modified charge-sensitive amplifier (CSA) that compensates for the effect of capacitance presented by nuclear radiation detectors and other sensors. For applications that require large area semiconductor detectors or for those semiconductor sensors derived from high permittivity materials such as PbSe, the detector capacitance can degrade the system gain and bandwidth of a front-end preamplifier, resulting in extended rise times and attenuated output voltage signals during pulse formation. In order to suppress the effect of sensor capacitance, we applied a bootstrap technique into a traditional CSA. The technique exploits the Miller effect by reducing the effective voltage difference between the two sides of a radiation detector which minimizes the capacitance presented to the differential common-source amplifier. This new configuration is successfully designed to produce effective gain even at high detector capacitance. The entire circuit, including a core CSA with feedback components and a bootstrap amplifier, are implemented in a 0.18 μm CMOS process with a 3.3 V supply voltage.