|Fig. 1: Basic Nuclear Power Plant Design. (Courtesy of the NRC. Source: Wikimedia Commons)|
The International Atomic Energy Agency is the global regulatory agency in charge of safety of nuclear power plants, however, it is also important that countries have their own checks and balances in order to maintain a high level of safety within plants. Plant structural stability is a key component in ensuring that nuclear plants are safe, this includes design and material selection. This report examines the design choices and material selection used for nuclear power plants, paying particular attention to the containment building.
Power plants are designed in order to contain radioactive fission products to prevent offsite health effects, and to ensure that heat generated by the plant is safely removed. There are three barriers set in place to contain the fission products from the environment: fuel cladding, reactor vessel and primary cooling system, and containment, seen in Fig. 1.  The containment building is made to withstand natural disasters and severe accidents. It is usually made of concrete that can be up to two meters thick. 
The concrete building is used as a last defense, and yet is vital especially with the possibility of natural disasters. Therefore, recently there have been a lot of advances to create concrete that is stronger, can withstand radiation and general material aging. 
In the past two decades nuclear concrete structures have undergone a large evolution, including material concrete, design methodology and construction techniques and maintenance and aging management.  High performance concrete has been created that has greater workability, strength and durability compared to the conventional normal strength concrete. In 2016 a study was published showing the positive effects of Fiber Reinforced Concrete (FRC), which has increased tensile strength, ductility and toughness. Furthermore, FRC helped impact- resistance of nuclear containment buildings compared to regular concrete. 
Construction methods have also significantly influenced the material properties of the concrete, therefore lots of research has gone into optimizing different protocols. Lastly managing aging to prevent or catch degradation is vital. Periodic inspections, testing maintenance and repair are all included in this. Right now there are three types of aging management that are used, including experience-based, regulatory-based and economic-based.
Although the IAEA has multiple protocols set in place to protect people and the environment, there are still many advances that can be made to help improve the structural stability of power plants. Natural disasters are the least predictable and yet one of the biggest causes of nuclear power plant disasters. Therefore, the improvement of containment buildings is key for the continued use of nuclear power plants.
© Lily Katz. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "Nuclear Power Plant Design Characteristics," International Atomic Energy Agency, IAEA-TECDOC-1544, March 2007
 P. C. Basu, P. Labbé, and D. J. Naus, "Nuclear Power Plant Concrete Structures," Transactions of the 22nd International Conference on Structural Mechanics in Reactor Technology, SMiRT-22, 18 Aug 13. August 2013.
 S. Jeon and B. Jin, "Improvement of Impact-Resistance of a Nuclear Containment Building Using Fiber Reinforced Concrete," Nucl. Eng. Des. 304 139 (2016).