Aspects of Bending High-Borated Austenitic Stainless Steel Sheets for Interim Storage of Spent Nuclear Fuel

The presented work is aimed at the evaluation of the cold bending capacity of high-borated austenitic stainless steel sheets. Due to their excellent neutron-absorbing capability, borated stainless steels belong to the group of tailor-made structural materials widely used for vertical storage baskets for holding spent nuclear fuel assemblies in cooling pools at dry or wet storage facilities. The basket consists of individual fuel assembly cells. Each polygonal cell is usually welded from several steel strips. It would be advantageous to use bent steel semi-product to avoid welded seams as much as possible. Welded seams are difficult to make, and moreover, they are susceptible to corrosion. However, high-borated stainless steels, because of their boron content, show limited hot and cold workability. Thus, their cold bending capacity would be the primary issue. Their austenitic matrix with embedded hard and brittle boride particles is prone to the evolution and fast propagation of dimple transgranular fracture. This work is focused on the bending aspects of borated steel sheets with respect to the most commonly used hexagonal cell geometry. Experimental results provide practical recommendations for the rack design. The damage criterion has also been proposed using FEM simulations in DEFORM (R).

Automated summary

The aim of this work is to evaluate the cold bending capacity of high-borated austenitic stainless steel sheets. Borated stainless steels, known for their excellent neutron-absorbing capability, are widely used in vertical storage baskets for spent nuclear fuel. Welded seams, which are difficult to make and prone to corrosion, could be minimized by using bent steel semi-products. However, the limited workability of high-borated stainless steels due to their boron content poses a challenge for cold bending. This study focuses on the bending aspects of borated steel sheets with hexagonal cell geometry and provides practical recommendations for rack design.