Validation of plant dynamics analysis code super-COPD for fast reactor core thermal hydraulics under natural circulation with PLANDTL experiment

Hamase, Erina ; Ono, Ayako ; Doda, Norihiro  ; Nabeshima, Kunihiko  ; Ohshima, Hiroyuki

In order to validate the one-dimensional thermal hydraulic analysis code, Super-COPD, the experiment under natural circulation (NC) conditions using the plant dynamics test loop (PLANDL) was analyzed. In the present analysis, all seven subassemblies in the PLANDTL core were modeled and each subassembly was divided into the center and peripheral region due to evaluate the radial heat transfer through the wrapper tube walls. Boundary conditions were as follows: the flow rate, the core inlet temperature and the heater power in each subassembly. As a result, the sodium temperature at the top of the heated region was in good agreement with the experiment. Furthermore, the scaling analysis was performed based on the top-down approach in the Hierarchical Two-Tiered Scaling. In the top-down approach, characteristic time ratios normalized the characteristic frequency of various transfer processes such as NC head, shape and friction loss, heat transfer and heat conduction etc. with the residence time in the core region were obtained by normalizing conservation equations of mass, momentum and energy. It was found that under NC, the largest characteristic time ratio was the one for NC head, or NC was the most important process in the core region. Then, the scale distortions of these characteristics time ratios between PLANDTL and MONJU were evaluated and thus the modeling performance of important process could be reconfirmed.