Investiation on presence of inner barrel for large fast breeder reactor

Muramatsu, Toshiharu

In-vessel thermohydraulics analysis was conducted for transient simulating a pump coast down and reactor scram (manual reactor trip event) to evaluate effects of an inner barrel on a large fast breeder reactor. Then four thermohydraulics phenomena, a thermal stratification, a main loop temperature transient, a circumferential temperature distribution and a sodium surface velocity were discussed. Through the analysis using the multi-dimensional code AQUA and the discussion, the following have been effects of the inner barrel as obtained: [Thermal Stratification] This phenomenon is not influenced very much on presence of an inner barrel. And appearance of an axial temperature distribution can be neglected from a structural design. [Main Loop Temperature Transient] An inner barrel is required. Because a cold shock with maximum temperature transient -2.0C/s occurred at a outlet nozzle when an inner barrel was not equipped. [Circumferential Temperature Distribution] This phenomenon is not influenced very much on presence of an inner barrel. And appearance of the temperature distribution can be neglected from a structural design. But further investigation on a thermal stress at reactor vessel is necessary. [Sodium Surface velocity] An inner barrel is unnecessary. From the above results, it is concluded that an inner barrel is unnecessary if the cold shock is improved by a increase of effective mixing region on a design.