Flow rate measurement in a high temperature, radioactive, and corrosive environment

Accurate measurement of coolant flow rate is essential for determining the maximum power required by the nuclear plant operation and critical for monitoring its operation safety. However, no practical off-the-shelf flowmeter is available to satisfy all the pressing multidimensional operation requirements (i. e., high temperature, high irradiation, and high corrosion). This work thus deals with the development of a new flowmeter for nuclear power plant/reactor process-monitoring and real time analysis; this proposed flowmeter shall be able to continuously conduct robust measurements under extremely harsh environment with high irradiation, high pressure, high temperature and corrosive media. We investigate a transit-time based flow rate measurement which is used in such environment. The transit time of a thermal signal travels along with a liquid flow can be obtained using a cross correlation method. This transit-time-based flowmeter using thermocouples with grounded stainless steel shielding is by far the most robust and reliable solution to measure the flow rate in a harsh environment typically seen in a nuclear reactor. In practice, cross correlation calculation tends to produce flat peak plateau or multiple peaks, leading to a significant error in peak detection. To overcome this problem, in this work, an Auto-Adaptive Impulse Response Function estimation (AAIRF) technique is introduced and a significantly narrower peak is shown theoretically and also verified experimentally. In addition, we show that more accurate results can be obtained if moving average filter based cross correlation function (MAFCCF) is combined with AAIRF. Also in this work, we investigate a few important practical problems related to negative delays and sampling frequencies of the data acquisition. The second part of this work deals with the calibration of the developed flowmeter which was mentioned above. To commission the flowmeter, calibration process is applied by comparing the reading measurements with a standard flowmeter measurement. In this work, this process is performed in an in house developed water-based test apparatus with a developed transit-time based flowmeter based on the measurement and processing of correlated thermal signals. In this system, we have observed that the accuracy of the measured flow is restricted to the time response of the thermocouples. In addition, since the flow rate is inversely proportional to estimated time delay, high flow rates measurement like 5 gpm (gallon per minute) requires large transit-time span that can not be achieved from a limited physical system dimensions. These problems are investigated through this work. In the final part of this work, as the ultrasonic flow measurement technologies including transit-time and Doppler effect technologies are usually used in harsh environments, we study these methods with intensive simulations

Analytical Models for Distribution of the Envelope and Phase of Linearly Modulated Signals in AWGN Channel

In this paper, analytical expressions for the distribution of the envelope and phase of linearly modulated signals such as BPSK, M-PSK, and M-QAM in AWGN are presented. We perform numerical simulations for different orders of signal constellations. The results show that the proposed theoretical models are in excellent agreement with the estimated distributions from various numerical experiments

« The electromagnetic interference of mobile phones on the function of a gamma camera »

Purpose: The aim of the present study is to evaluate whether or not the electromagnetic field generated by mobile phones interferes with the function of a single-photon emission computed tomography (SPECT) gamma camera during data acquisition. Methods and materials: We tested the effects of seven models of mobile phones on one SPECT gamma camera. The mobile phones were tested when making a call, in ringing mode, and in standby mode. The gamma camera function was assessed during data acquisition from a planar source and a point source of technetium-99m with activities of 10 mCi and 3 mCi, respectively. A significant decrease in count number was considered to be electromagnetic interference (EMI). Results: The percentage of induced EMI with the gamma camera per mobile phone was in the range of 0–100%. The incidence of EMI was mainly observed in the first seconds of ringing and then mitigated in the following frames. Conclusion: Mobile phones are portable sources of electromagnetic radiation, and there is interference potential with the function of SPECT gamma cameras leading to adverse effects on the quality of the acquired images. Keywords: Electromagnetic interference (EMI), mobile phones, gamma camera, single-photon emission computed tomography (SPECT

Performance Evaluation of a narrowband Power Line Communication for Smart Grid with noise Reduction Technique

Performance of the narrowband power line communication (PLC) is significantly degraded by the impulsive noise with very large amplitudes and short durations. In practical applications, the simple memoryless nonlinearity techniques (Clipping, Blanking, and Clipping/Blanking) are often used in order to mitigate the effect of the impulsive noise. In this paper, we propose an optimal Clipping/Blanking technique for impulsive noise reduction in narrowband (9-490 kHz) PLC system. This optimal technique is based on the minimum bit error rate (BER) search. To this end, we have derived the transfer function of a typical low voltage (LV) PLC network using the common bottom-up approach and scattering matrix method. Our simulation results, in terms of BER versus signal to noise ratio (SNR), show that the proposed technique slightly improves the BER performance of the narrowband PLC system for smart grid applications and two-way communication between smart meters and utilities

A Novel Multi-Exponential Function-based Companding Technique for Uniform Signal Compression over Channels with Limited Dynamic Range

Companding, as a variant of audio level compression, can help reduce the dynamic range of an audio signal. In analog (digital) systems, this can increase the signal-to-noise ratio (signal to quantization noise ratio) achieved during transmission. The μ-law algorithm that is primarily used in the digital telecommunication systems of North America and Japan, adapts a companding scheme that can expand small signals and compress large signals especially at the presence of high peak signals. In this paper, we present a novel multi-exponential companding function that can achieve more uniform compression on both large and small signals so that the relative signal strength over the time is preserved. That is, although larger signals may get considerably compressed, unlike μ-law algorithm, it is guaranteed that these signals after companding will definitely not be smaller than expanded signals that were originally small. Performance of the proposed algorithm is compared with μ-law using real audio signal, and results show that the proposed companding algorithm can achieve much smaller quantization errors with a modest increase in computation time

Measurement and Calibration of Thermal Cross-correlation-based Flowmeter Operating in Harsh Environment

In the harsh environment present in nuclear reactors, due to degradation caused by corrosion and/or erosion, the available nonintrusive flow rate measurement devices are capable of working only for a short period of time. The transit-time-based flowmeter using thermocouples (TC) with grounded stainless steel shielding is by far the most robust and reliable solution to this problem. This method suffers from a few signal processing problems, such as flat peak plateau or multiple peaks that result in wrong transit-time estimation. We have previously introduced a signal processing technique to correct the transit time estimation. However, as we conducted experiments, the calculated flowrates using the estimated transit-time are not in good agreement with readings from a standard flowmeter. To adjust the calculated flow, in this paper, we apply a regression method through the calibration process with measurements obtained from a standard flowmeter using an in-house developed apparatus. We observe a nearly linear relationship between the readings from the standard flowmeter and those from our flowmeter for flowrates ranging from 0.5-3 gpm (gallon per minute). The calibration results are quite consistent across different experiment scenarios

Statistical Model Based SNR Estimation Method for Speech Signals

The performance of speech enhancement algorithms to a large extent is related to the employed signal-to-noise ratio (SNR) estimation techniques. Many of the existing SNR estimation techniques are based on approaches that require either an experimentally pre-specified weighting factor or prior assumptions of the parameters in the signal model. In this reported work, a closed form SNR estimator is derived by modelling the noisy speech signal as a generalised normal-Laplace distribution and estimating the variance of the signal and variance of the noise using high-order sample moments. The performance of the proposed technique is tested using real speech signals and compared with the well-known eigenvalue method

Flow Rate Measurement in a High-temperature, Radioactive, and Corrosive Environment

The transit time of a thermal signal traveling along with a liquid flow can be obtained using a cross-correlation method. This transit-time-based flowmeter using thermocouples with grounded stainless steel shielding is by far the most robust and reliable solution to measure the flow rate in a harsh environment of high temperature, irradiation, and corrosion, typically seen in a nuclear reactor. In practice, cross-correlation calculation tends to produce flat peak plateau or multiple peaks, leading to a significant error in peak detection. To overcome this problem, in this paper, an autoadaptive impulse response function (AAIRF) estimation technique is thus introduced, and a significantly narrower peak is shown theoretically and also verified experimentally. In addition, we show that more accurate results can be obtained if a moving-average-filter-based cross-correlation function is combined with AAIRF. In this paper, we also investigate a few important practical problems related to negative delays and sampling frequencies of the data acquisition

Detection Algorithms for the nano nose

The nano nose is an instrument with an array of nano sized optical sensors that produces digital patterns when exposed to radiation passing through a gaseous mixture. This paper outlines an algorithm using a combination of neural networks and partial least squares (PLS) regression, Kalman filter capable of processing these digital patterns and generate an output. This output would not only show the detection of the individual constituents in the gaseous mixture but also the prediction of their concentrations. The developed algorithm in the experiments conducted, has performed detection and prediction of quite low concentrations of constituent gases successfully with a prediction error of less than 10% in the presence of noise