Mock-up wall for non-destructive testing and evaluation of thick reinforced concrete structures in nuclear power plants

The reinforced concrete structures in nuclear power plants (NPP) are deteriorated due to aging or environmental stressor effects during the lifetime of the power plant. To assess the construction quality and long-term performance of the reinforced concrete structures, different non-destructive testing (NDT) and evaluation (NDE) methods are used. Some of the challenges for assessing the performance of these structures are (i) The assessment could be performed only during the annual overhauls when testing is time-limited, (ii) the accuracy and reliability of the available NDT testing devices, (iii) uncertainty of the international uniformity of the methods used for NDT tests, and (iv) the creditability of results and analyses. To overcome those challenges, a mock-up wall that is representative of NPP containment concrete cross sections is constructed for the critical investigation of NDT&E methods and techniques. Simulated defects are applied to the mock-up wall. These defects are representing the most common types of defects in concrete structures such as: dimensional errors; finishing errors; honeycombing; cracking, delamination due to structure stresses or deterioration mechanisms; embedded foreign objects in the concrete; voids adjacent to liner and voids in grouted tendon ducts for the post-tensioned structures. The aim of this paper is to present to discuss the conceptual design of the mock-up, which includes (i) the concrete properties, (ii) reinforcement, (ii) tendon ducts, (iii) types of the simulated defects. The paper also introduces the NDT&E methods and techniques that are suitable for assessing the condition of the mock-up wall under the real environmental conditions. The mock-up wall for NPP thick-walled reinforced concrete structures will enable the assessment of NDT&E methods and experts experience, and provide an important and very much need education perspective for future NDE experts.