Evaluation of the mechanical properties of irradiated NPP's structural materials using semidestructive testing method

Determination of current mechanical properties of several structural materials of NPP components, especially reactor internals, is not possible using the standard testing methods, in connection with the material volume necessary for the testing. Sampling of the optimal material volume usually brings adverse consequences of affecting the integrity of component or in several cases destruction of the whole evaluated component. For standard size specimens, it is also necessary to take into account the high activity of the material, with influence on the collective dose of hot cell facilities personnel. In comparison with reactor pressure vessel, reactor internals are not covered by the system of surveillance samples as well as other hardly replaceable components of the primary circuit, e.g. primary piping, steam generator etc. Monitoring the mechanical properties changes is very important to assure structural integrity of NPP components, especially within the context of their operational life extension. Aim of this work is to present the advantages of the semi-destructive testing methods (small punch tests, automated ball indentation test) in the process current mechanical properties evaluation of the hardly replaceable long-term operated NPP components, mainly reactor internals, primary piping, steam generators and reactor pressure vessels. Semi-destructive testing techniques use technological processes and equipment enabling the direct determination of mechanical properties from the component surface without affecting its integrity. Advantage of semi-destructive degradation mechanisms quantification could be very promising for use in the field of nuclear energy for components of NPP as well as in other industrial sectors, e.g. chemical and petrochemical industry.