Abstract
Nondestructive evaluation (NDE) methods are widely used for inspecting safety relevant components in nuclear reactors. Most of these NDE-methods are optimized and applied for the detection of cracks but there is still no reliable NDE method for measuring the embrittlement of RPV steels. However, since the evaluation of RPV embrittlement of so-called Surveillance specimens with the Charpy test is a destructive approach, NDE methods are highly required. Among the investigated technics are acoustic (Ultrasonic scattering), electric (resistivity, thermoelectric) and magnetic (Barkhausen Noise, Non-Linear Harmonics Analysis, Micromagnetic Multiparameter) methods. However, all the methods under investigation suffer from the fact that fracture toughness of steel depends upon several factors, especially on lattice defects such as vacancies, dissolved atoms, dislocation loops, solute clusters, precipitates and dislocations. A major obstacle to the application of NDE methods for the quantification of material embrittlement is that they may be not only sensitive to these defects but also to other factors, such as magnetic, acoustic and electrical properties, as well as to surface quality and ambient temperature, etc.).
In this paper, we present results gained by the optimization and application of the thermoelectric power method (TEPM) at the Paul Scherrer Institut (PSI) in Switzerland. The TEPM uses the change of the Seebeck coefficient (K) as an indicator for the material embrittlement. A clear almost linear correlation between the shift of the Nil-Ductile-Transition-Temperature (NDTT) and the change of the K was found. Beside the TEPM and its optimization with the finite element method, we describe the influencing parameters and the potential of this promising NDE method.
Non-destructive Investigation of “The Violinist” a Lead Sculpture by Pablo Gargallo, Using the Neutron Imaging Facility NEUTRA in the Paul Scherrer Institute
