高温ガス炉の１次冷却系主配管破断事故時の空気浸入挙動，（ＩＩ） 炉心の黒鉛流路管温度が非均一の場合

Abstract

A primary pipe rupture accident is one of the design-basis accidents of a High-Temperature Gas Cooled Reactor (HTGR). When the primary pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. During the accident a complicated multi-component gas flow is expected to occur in the reactor vessel. This paper deals with experimental study on the process of air ingress into an apparatus simulating the HTGR during the 1st stage of the accident. Present study focuses on investigating the density change of the gas mixture, concentration change of each gas species, and duration of the 1st stage of the accident when the temperature of the central flow path is higher than that of the peripheral ones and when the temperature of the reactor simulator decreases with time after the pipe rupture accident. It was found that the cooling rate of the reactor core temperature for preventing natural circulation of air existed. The results of the density and concentration changes in the non-uniform temperature case are almost the same as those in the uniform temperature case if natural circulation does not occur in the reactor core flow paths.