Infrared detection systems, basic

Figure 2. Common components of basic infrared detection systems. The illustration shows examples of three typical infrared energy inputs.

Another ongoing item on the steam generator safety is a leak detection system development for the double wall tube that is being developed for the steam generator installed in a primary heat transport system of a future FBR plant. Basic performance data was obtained for an outer tube leak detection system to detect helium leak into sodium. An inner tube leak detection system using infrared rays is also under developing to quickly detect humidity at gas plenums. 

The research activity here presented has been carried out at the N.D.T. laboratory of l.S.P.E.S.L. (National Institute for Occupational Safety and Prevention) and it is aimed at the set up of the Stress Pattern Analysis by Measuring Thermal Emission technique [I] applied to pressure vessels. Basically, the SPATE system detects the infrared flux emitted from points resulting from the minute temperature changes in a cyclically stressed structure or component. 

Gas monitoring systems should be chosen to suit their intended use since significant differences exist between available sensing technologies, price, and performance. There are basically two types of gas detection technologies. With instrumentation monitors, a sample of air is drawn through a piece of tubing, the sample draw line, to an analysis instrument, which is most commonly based on mass spectrometry, flame emission spectrometry, infrared spectrometry, or colorimetric (paper tape) response. 

This article provides some general remarks on detection requirements for FIA and related techniques and outlines the basic features of the most commonly used detection principles, including optical methods (namely, ultraviolet (UV)-visible spectrophotometry, spectrofluorimetry, chemiluminescence (CL), infrared (IR) spectroscopy, and atomic absorption/emission spectrometry) and electrochemical techniques such as potentiometry, amperometry, voltammetry, and stripping analysis methods. Very few flowing stream applications involve other detection techniques. In this respect, measurement of physical properties such as the refractive index, surface tension, and optical rotation, as well as the a-, //-, or y-emission of radionuclides, should be underlined. Piezoelectric quartz crystal detectors, thermal lens spectroscopy, photoacoustic spectroscopy, surface-enhanced Raman spectroscopy, and conductometric detection have also been coupled to flow systems, with notable advantages in terms of automation, precision, and sampling rate in comparison with the manual counterparts. 

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