Thermal-Hydraulic Characteristics of Coolant in the Core Bottom Structure of the High-Temperature Engineering Test Reactor

The high-temperature engineering test reactor (HTTR) is a 30-MW(thermal) helium gas-cooled reactor being constructed by the Japan Atomic Energy Research Establishment. A thermal mixing study of the coolant in the core bottom structure (CBS) of the HTTR is conducted to clarify the thermal-hydraulic characteristics of the coolant and estimate the influence of a hot streak on the intermediate heat exchanger (IHX) and a pressurized water cooler (PWC) downstream from the core. An experiment is carried out using an in-core structure test section (a full-scale simulation model of the CBS) of the helium engineering demonstration loop (HENDEL), and a numerical analysis is made using a three-dimensional time-dependent flow and heat transfer code including a k-ε model of turbulence. It is confirmed that the coolant is mixed sufficiently in the CBS and the outlet gas duct of the HTTR, and the hot streak had little effect on the IHX and the PWC.