“NDT MATRIX” - A Tool for Selecting Non-Destructive Testing Methods for NPP Concrete Structures

In nuclear power plants concrete structures are exposed to a variety of environments and affected by different deterioration processes during their life time. To ensure the integrity of the concrete components, especially with regard to the extension of the life-span of nuclear plants, the use of non-destructive testing (NDT) methods are essential for examining the concrete and the reinforcement embedded. However, current NDT techniques face several challenges: (i) NDT inspection can be performed only during the annual overhauls when testing is time-limited, (ii) the accuracy of NDT testing devices, (iii) uncertainty of the global uniformity of the methods used for NDT tests, and (iv) the creditability of results and analyses. An effective inspection of concrete components is only possible if the deterioration processes are defined and the reliable and relevant NDT testing techniques are provided.
The aim of this paper is to describe a tool for selecting suitable non-destructive testing methods for structural components of concrete in NPPs based on their age and possible degradation mechanism. The paper also aims to critically assess the NDT techniques currently available for non-destructive testing of NPP concrete structures that fulfil the needs of NPP infrastructure evaluation in Finland.
The tool includes representations of (i) the building materials used in the structural components, (ii) the ageing defects affecting the NPP concrete structures, (iii) the available NDT techniques and (iv) the inspection schedule for concrete structures recommended for Finnish NPPs. The tool developed suggests reliable and reasonable non-destructive test techniques for nuclear power companies and utilities to ensure the safety of the nuclear power plant facilities.