Study for thermal mixing of coolant in a core-bottom structure of HTTR, 1

The numerical and experimental studies were conducted to clarify the thermal mixing performance of a coolant in the core-bottom structure of HTTR (High Temperature engineering Test Reactor) being developed in JAERI. The experimental study was carried out using a one-seventh scale model of the core-bottom structure and water as testing fluid. The experimental conditions were as follows: the temperature differences between hot and cold water at the inlet of the test section were 20 ∼ 40 deg C, and Reynolds number calculated with the diameter of the outlet nozzle was 40,000 ∼ 100,000. The numerical study was made using a three dimensional time-dependent flow and heat transfer code named STREAM. In order to evaluate the validity of the STREAM code, the numerical results were compared with the experimental ones. The both results were in good agreement and it was confirmed that the STREAM code was able to use the prediction of the thermal mixing in the core-bottom structure of HTTR. (author)