Integrity evaluation analysis of nuclear plant piping at heavy equipment impact

Abstract

Safety assessments of nuclear plants against tsunamis have been reviewed after the Fukushima Daiichi nuclear disaster caused by a tsunami during the Great East Japan Earthquake in March 2011. These assessments are required for the restarting of operations at nuclear plants. Integrity evaluations of nuclear plant facilities at impact of floating debris caused by a tsunami are performed on the basis of the estimated strain on a facility caused by the impact force. In this paper, drop impact tests were carried out using real scale specimens of a delivery pipe and a power supply unit that nuclear plant facilities comprise. A 1500-kg power supply unit impacted on a delivery pipe (318-mm in diameter, 5-m in length) under two impact speed conditions of 5.2 and 9.5 m/s. No noticeable penetration damage to the pipe was detected under either condition. Simulated results considering strain rate dependence and constitutive equations with power hardening law showed good agreement with the experimental results. This simulation model is effective to analyze the safety margin of apparatuses at impact.