Thermal-hydrauic Analyses of Moderators

 
 Thermal-hydraulic design requirements for moderators are to prevent boiling of hydrogen and to suppress hot spots decreasing neutronic performance. As a result of a conceptual design study, impinging jet is used to remove high heat deposited on the bottom wall of moderator vessel near target. It is necessary to reduce re-circulation and stagnant flows which cause hot spots in the hydrogen flow so as to suppress the temperature rise of hydrogen in the moderator vessel within 3K. Thermal-hydraulic analyses, as well as experiments have been carried out to prove the feasibility of this concept. 

  The analyses show that the local temperature rise in the re-circulation and stagnant flow regions could be suppressed within 3K. The hydrogen temperature increases up to 26K adjacent to the vessel surface due to nuclear heating of the vessel. This hot layer, however, would not change the neutronic performance because its thickness is very thin of less than 0.3mm. 

　


Overview of Flow Visualization Experiments

　


Flow Visualization Experiments (Flat type vessel)

　


　


Flow Analyses (Flat Type Vessel) 1

　


　


Flow Analyses (Flat Type Vessel) 2

　

　


Thermal-hydraulic Analysis for New Designed Vessel 1

　


　


Thermal-hydraulic Analysis for New Designed Vessel 2

　

　


Thermal-hydraulic Analysis for Decoupled Moderator Vessel

　


　


Thermal-hydraulic Analysis for Coupled Moderator Vessel

　


　


Flow Visualization Experiments (Flat type vessel) 

　

　


Flow Analyses (Cylindrical type vessel)

　


　


Experimental and Analytical Results of Velocity Distributions (1) 

　


　


Experimental and Analytical Results of Velocity Distributions (2) 

　


　


Heat Transfer Experiments under Impinging Jet in Limited Space

　


　


Preliminary Experimental and Analytical Results

　


　


Drawing of Coupled Moderator Vessel

　

　


Drawing of Decoupled Moderator Vessel