Severe accident measures technique by response control for nuclear piping using coil spring damper

It is highly requested to suggest measures to severe accident when input motion level exceeds the design basis earthquake based on experience of the accident in Fukushima. However, there is a limit to heighten the strength of the structure in order to enhance the seismic safety. In generally, as metal material has elastic and plastic deformation ranges, it is known that the latter shows wider deformation range than the former. All mechanical components are generally designed to behavior in elastic range for function maintenance while some mechanical components are fine to reflect elasto-plastic elements. Of most well-known is piping support element. It increases safety of the piping as piping support element deforms plastically by absorbing the energy when responding to the earthquake. It is considered one of the best-possible measures to secure the safety level in the area beyond the design basic accident such as severe accident measures. This study reviewed the vibration control capacity of the piping system by using the elasto-plastic damper. This paper compares the analytical model of the coil spring damper with the mechanical characteristics obtained from the experiments. Test result agrees well with the basic mechanical characteristic of the elasto-plastic damper. This paper discusses on the challenge of thermal expansion from pipe support area and their responses during earthquake. (author)