Experimental study of flow inversion in MTR upward flow research reactors

Abstract

The core cooling of upward flow MTR pool type Research Reactor (RR) at the later stage of pump coast down is experimentally handled to clarify the effect of some operating parameters on RR core cooling. Therefore, a test rig is designed and built to simulate the core cooling loop at this stage. The core is simulated as two vertical channels, electrically heated, and extended between upper and lower plenums. Two elevated tanks filled with water are connected to the two plenums. The first one constitutes a left branch, connected to the lower plenum, and is electrically heated to simulate the core return pipe. The second one constitutes the right branch, connected to the upper plenum, and is cooled by refrigerant circuit to simulate the reactor pool. Channel coolant and wall temperatures at different power and branch temperatures are measured, registered and analyzed. The results show that at this stage of core cooling two cooling loops are established; an internal circulation loop between the channels dominated by the difference in channel's power and an external circulation loop between the branches dominated by the temperature difference between branches. Also, there is a double inversion in core flow, upward-downward-upward flow. This double inversion increases largely the channel's wall temperature. Complementary safety analysis to evaluate this phenomenon must be performed.

Validation of RELAP5 model of experimental test rig simulating the natural convection in MTR research reactors

“…This paper is the second part of a study handled the flow inversion in upward flow MTR pool type research reactors immediately after pump coast down. In the first part, an experimental work consisting of built up of a test rig simulating the cooling loop after pump coast down aims to study the effect of environmental and operating conditions on the buildup of core natural convection [9]. The present paper complements the first one and introduces theoretical simulation and analysis for the test rig with using RELAP5 MOD3.3 thermal hydraulic system code.…”