Analysis of the Aging of Buried Pipes of a Boiling Water Reactor Nuclear Power Plant Due to the Thinning of Their Wall Thickness

The failure causes of buried pipes, which are part of the open cycle cooling system in a boiling water reactor nuclear power plant, are related to corrosion by erosion. They are generated by the continuous flow of seawater, and soil-side corrosion. Also, the dead load, produced by the soil weight on the pipeline, and the live loads, gradually influence on the aging of the pipes. Such live loads are generated by the weight of vehicles that circulate on the transit routes in the nuclear plant. The continued damage of the interior and exterior surfaces of a buried pipe, and the critical cyclic loading conditions can contribute to the initiation of cracks. Regarding this paper, the structural integrity of a buried pipe was evaluated after 30, 40, and 60 years of operation. It was considered the critical load conditions and the loss of wall thickness. The last situation directly affects the internal and external diameter dimensions. The ASME code was followed in the estimation of the internal wall thinning. For the soil-side corrosion, it was applied a statistical model, which predicts the corrosion rate.