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Concrete, an integral part of a nuclear power plant (NPP), experiences degradation during their operational lifetime of the plant. In this review, the major causes of concrete degradation are extensively discussed including mechanisms that are specific to NPPs. The damage mechanism could be chemical or physical. The major causes of chemical degradation include alkali–aggregate reactions, leaching, sulfate attack, bases and acids attack, and carbonation. Physical degradation is a consequence of both environmental and mechanical factors combined. These factors are mainly elevated temperature, radiation, abrasion and erosion, salt crystallization, freeze–thaw distortions, fatigue and vibration. Additionally, steel reinforcements, prestressing steels, liner plates, and structural steel also experience degradation. The prospective areas in the structural components of the NPP where the degradation could occur are mentioned and the effective solutions to the causes of degradation are highlighted. These solutions are designed to enhance the physical and chemical characteristics of concrete. Some of the major recommendations include addition of mineral substitutes, use of low water-to-cement ratio as well as low water-to-binder ratio, use of low alkali cement, use of special aggregates and fibers, use of corrosion inhibitors, use of cathodic protection, etc. The review concludes with an overview of present methods and possible recommendations used to enhance the quality of concrete towards preventing concrete degradation and increasing the lifetime of NPPs.

A study on the use of amorphous metallic fibers (AMFs) in concrete was undertaken to combine its action with that of hooked-ended steel fibers for improving flexural strength and toughness. Tests on mixtures with various dosages of AMF (10, 20, and 30 kg/m^sup 3^ [16.9, 33.7, and 50.6 lb/yd^sup 3^]), and 15 kg/m^sup 3^ (25.3 lb/yd^sup 3^) of steel fibers were carried out, along with hybrid mixtures with two dosages of AMF. The results showed a significant increase in the flexural strength of concrete with the addition of AMF, even at low dosages. The performance of concretes with the hybrid combinations is significantly enhanced. For example, the equivalent flexural strength for the concretes with just 10 kg/m^sup 3^ (16.9 lb/yd^sup 3^) of AMF and 15 kg/m^sup 3^ (25.3 lb/yd^sup 3^) of steel fibers is 35% higher than with only steel fibers and is approximately 3.5 times that obtained with only 10 kg/m^sup 3^ (16.9 lb/yd^sup 3^) of AMF. The load-deflection behavior and the toughness parameters clearly indicate a significant synergy in the hybrid combination.