Paper: Comparison of Approaches for Evaluation of Accidental Load Drops

Assessing impact on nuclear power plant structures


An accidental load drop during load handling could impact the safety of the nuclear plant structures or safety-related equipment and cause inadvertent criticality, or loss of safe shutdown equipment. In this paper, available approaches for evaluation of the structural members due to impact of an accidental load drop in U.S. nuclear power plants are evaluated. Consideration is given to the limitations of the approaches imposed by the NUREG-0612 (1980).

The paper discusses the two common approaches that can be used to evaluate the impact: the first approach is to calculate the elasto-plastic energy absorption capacity of the member and compare it to the energy imparted during impact. The second is to estimate the applied force on the impacted member considering the penetration of the load into the target using empirical formulas. The limitations of each approach are demonstrated by evaluation of a hypothetical structural beam. Both approaches are investigated to calculate the allowable load at a given drop height for various drop locations along the beam centerline, as well as off-centerline of the beam. Additionally, a sensitivity study is performed to consider the effect of boundary conditions on the results in terms of the load drop capacity.

Based on the results of the analysis, recommendations are given for the proper selection of the approach to estimate the allowable drop load based on the load drop location.

Asadollah Bassam, Javad Moslemian – Sargent & Lundy

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