Tadashi Amakawa

CFD Calculation of Pressure Rise Due to Internal AC and DC Arcing in a Closed Container

Computational fluid dynamics calculation results of pressure rise and propagation due to high-current arcs in a closed container are described. The pressure developments at different locations within the container are calculated by changing the current frequency (ac of 50 and 60 Hz, and dc) and the electric arc energy input (up to approximately 1000 kJ). The local pressure oscillation amplitude for AC/50 Hz within the container exceeds that for dc. From the pressure oscillation period and the sound speed distribution in the container, the following conclusions are made. With growing electric arc energy, the pressure amplitude increases because of the resonance effect between the arc power oscillation and pressure waves reflected on the walls. When the electric arc energy reaches a value of around 500 kJ, the pressure amplitude rises significantly. This is considered attributable to superimposition of pressure waves near the container wall caused by low propagation velocity of the pressure waves near the wall. It is necessary to consider this phenomenon for public safety when designing electric power equipment.

Reduction in Pressure Rise Due to Internal Arcing Using Melting and Vaporization of Metal

Summary form only given. When an arc is ignited between the electrodes in a closed chamber, the internal pressure rises. In this paper, the reduction in the pressure rise due to internal arcing using the melting and vaporization of a de-energized metal plate was investigated experimentally. The results showed that allowing a Cu or Fe plate placed near the electrodes to be melted and vaporized by the arc, the reduction in the pressure rise increased as the amount of mass loss of the plate increased. The decrease level of the maximum pressure rise was more than 20% on average in our experiments. On the basis of these experimental results, the energy balance in the closed chamber was estimated in order to clarify the mechanism behind the reduction in the pressure rise. The dominant cause of the reduction in the pressure rise for the Cu plate was the increase in energy consumption by the melting and vaporization of the plate. For the Fe plate, it was the increase in the energy of consumption by the arc radiation.

Electrical and mechanical properties in epoxy resin after gamma-radiation and LOCA simulation

Electrical and mechanical properties of three kinds of epoxy resin were investigated after gamma-radiation and LOCA simulation. The three kinds of epoxy resin were Bisphenol-A class (designated R1), Phenol Novolac Type (R-2), and Bismaleimide Triazine modified Type (R-3). Bismaleimide Triazine modified Type was estimated to be excellent for an insulating material used in a primary container vessel (PCV). Then, a composite of R-3 with Nomex base was prepared for testing as a better insulating system for a LOCA in PCV. This composite also showed excellent electrical and mechanical properties for LOCA simulation.

Reduction in pressure rise due to internal arcing using melting and vaporization of metal

When an arc is ignited between the electrodes in a closed chamber, the internal pressure rises. In this paper, the reduction in the pressure rise due to internal arcing using the melting and vaporization of a de-energized metal plate was investigated experimentally. The results showed that allowing a Cu or Fe plate placed near the electrodes to be melted and vaporized by the arc, the reduction in the pressure rise increased as the amount of mass loss of the plate increased. The decrease level of the maximum pressure rise was more than 20% on average in our experiments. On the basis of these experimental results, the energy balance in the closed chamber was estimated in order to clarify the mechanism behind the reduction in the pressure rise. The dominant cause of the reduction in the pressure rise for the Cu plate was the increase in energy consumption by the melting and vaporization of the plate. For the Fe plate, it was the increase in the energy of consumption by the arc radiation.