Using Acoustic Emission in Quality Control of Glass and Ceramics for Radioactive Waste Immobilization
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8VLQJ$FRXVWLF(PLVVLRQLQ4XDOLW\&RQWURORI*ODVVDQG&HUDPLFVIRU 5DGLRDFWLYH:DVWH,PPRELOL]DWLRQ V.Z.Belov, A.S.Aloy V. G. Khlopin Radium Institute (KRI), 28 2-nd Murinskiy Ave., St. Petersburg, 194021, Russia $%675$&7 Laboratory scale unit for registration of acoustic emission (AE) signals was used for integrity control of glass granules and ceramic bodies. AE waveform recorded in course of the temperature changes has been shown to allow for an unambiguous interpretation and may be used for nondestructive quality control of glass and ceramics bodies. Key words: acoustic emission, integrity control waste form. ,1752'8&7,21 For conditioned waste forms dimensional changes could occur from the time of processing as a result of temperature gradient or chemical reactions during curing. Dimensional changes may result either in shrinkage or swelling and produce deformation or cracks inside of waste form and package. For vitrified wastes as well as for ceramics the rate of temperature changes has a very significant influence on cracks formation. To minimize this process quality control in situ should be apllied. Nondestructive test methods are of considerable current use. One of such promising methods is AE, which constitutes in radiation of elastic waves by solids under the action of a force [1]. The processes accompanied by the emission of elastic waves are initiation, propagation and annihilation of dislocations and other lattice defects, plastic deformation, formation and propagation of cracks etc. The major advantages of the AE method are the following: 1. High sensitivity; 2. Capability to detect and keep track of defects in their progress; 3. Capability to control objects with stationary detectors instead of scanning; 4. Simplicity of use in course of technological operations which provides a way to the adaptive process control; 5. Capability to control products made of different materials including homogeneous, heterogeneous and composite; 6. High radiation and heat resistance of ceramic piezoelectric transducers used in detectors of the acoustic emission signals [2]. The AE signal amplitude of cracks developed to 0.01÷0.1 mm is a hundred times more that of the ultrasonic signal reflected from the same developing crack when the routine ultrasonic method is used. The maximum sensitivity of the method obtained in the laboratory study of the fatigue cracks growth ranged up to 0.025 mcm/cycle.
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(;3(5,0(17$/ The laboratory scale unit for recording acoustic emission signals consisted of separate modules and units interconnected in accordance with the diagram shown in Figure 1. A vertical electric resistance furnace uppere of working pad (1) was used as a heating unit. Depending on the purpose of the experiment in the heating zone was placed either the crucible with a bottom drain to cast glass granules or the upper (“hot”) part of the ceramic acoustic duct with a working pad to place the tested ceramic samples [3,4]. The previously melted glasses of different composition were used as source materials
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