Impact analysis of the package having additional protector of orifice near the containment boundary of the primary lid in the drop test II

It is common to determine the suitability of drop test II as defined by the IAEA Specific Safety Requirements No.SSR-6 paragraph 727 for the condition in which the center of a vessel body or lid impacts a mild steel bar as it is considered to cause maximum damage. However, in case the package has an orifice protector (hereafter referred to as "protector") on the orifice cover, which constitutes a containment boundary, it is possible that the orifice cover will sustain damage. When a mild steel bar impacts the vicinity of the orifice, the protector could separate causing the mild steel bar to directly impact the orifice cover. The behavior of the package when it impacts the mild steel bar through the protector was investigated. Case studies were conducted with finite element analyses (FEA) of a detailed model of the vicinity of the primarily lid and the protector. The parameters of the case study were the impact angles, impact points, and weld joint efficiencies between the protector and the cover plate of the shock absorber. The FEA indicated that for some values of weld joint efficiency, the protector got separated owing to a rupture of the welding joint and the orifice cover protecting the orifice was directly impacted by the mild steel bar, producing a large amount of stress in the orifice cover. Damage to the orifice cover is a concern. It was therefore concluded that it is necessary to consider an impact between the protector and the mild steel bar in drop test II for a package that has the protector on the primary lid. (author)