الفهرس 
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Abstract
This study investigates the applicability of acoustic emission in nuclear field. Major part of the energy released in fission reaction is roduced in the fuel elements, consequently these elements are subjected to thermal stresses that may develop radial and circumferential cracks and probably cen- teral holes. Acoustic mission (AE) is the detected elastic energy released when certain kinds of materials undergo deformation. When these materials subjected to external or internal tresses, three types of elastic waves may be produced and known as dialation, distortional and surface waves. The amplitude and frequency of these waves depends on the material properties. These waves can be detected by special transducers connected tG an effiecient measuring system. In power reactors, usually U02 pellets are used in manufacturing the fuel elements, as a result of the fission energy released within the fuel element; it will suffer temperature gradients in both axial and radial directions. The last one is much steeper than the former and onsequently thermal streiS components will be produced in R, g and Z directions. Assuming that the fuel element material is completly
isotropic elastic material, one can apply Hook:s Law of elasticity on stress-strain relations. Applying
balance equation at any point of certain cross section of the fuel element, one Cdn get the radial
displacement of fuel material
(U ), which depends r on the emperature distribution in that direction. Moreover, by applying the thermoelastic stress-
strain relations, one can get the stress components in R,g and Z directions. Obviously both displace-
ment and stress components could be evaluated in both steady state and dynamic operation. Different
boundary and initial conditions could be applied to the different equations expressing temperature, <stress and displacement distributions. These equa- tions can be solved numerically by finite difference
calculations. A computer code, SAL-HAM Code has been const- ructed to solve the numerical equations. The code
involves a main program and nine subroutines With an input data adapted from Main Ynkee nuclear power’plant, the code was tested successful_
ly in the case of normal and dynamic operations, results were obtained. Among these results are: i) Radial temperature distribution.