Temperature Effect on Heated Region Flow Starvation for Gas-Cooled Reactors

摘要

The Gas-Cooled Fast Reactor (GFR) is one of the sixGeneration-IV systems that was chosen to be developedby the Generation-IV International Forum (GIF), based onits ability to meet the Generation-IV goals. One of theGFR designs has a block-type core with circular coolantchannels that is similar to the prismatic block type coreused in the General Atomics Gas Turbine ModularHelium Reactor (GT-MHR). Recent studies [1] haverevealed that during off-normal conditions (e.g., Loss OfCoolant Accident) flow instability can occur within thehot channels resulting in choked flow. The choked flowdiffers from the traditional definition of choked flow as itis the result of a phenomenon called “laminarization”.Laminarization is caused when the coolant velocity istheoretically in the turbulent regime, but the heat transferproperties are indicative of the coolant velocity being inthe laminar regime [2]. It is important to examine thepotential for laminarization in the GFR design because, asa first approximation, the helium’s operating temperaturesappear conducive to the phenomenon’s occurrence. Thatis, the high heating rate of the GFR core results in thehelium’s elevated temperatures, acceleration, andviscosity; ideal conditions for the onset of laminarization.In this paper, we propose to study the effects oflaminarization by keeping the helium mass flow rateconstant, while increasing the temperature. With thisapproach we hope to identify which of the four variables(Reynold’s number, heat flux, buoyancy parameter, andacceleration parameter) are most influential in creatinglaminarization and, thus, hot channel instability.