Shaping of a gas-cooled reactor core using heat exchange intensifiers
The need for shaping the reactor cores by the coolant flow distribution arises due to the fulfillment of the requirements for the temperature fields in the core components [1 - 3]. However, shaping the core of any reactor inevitably leads to an increase in the pressure drop inside of the core and in the energy consumption to provide for the primary coolant circulation. This naturally involves the selection of the shaping principle (condition) in a combination with installation of heat exchange intensifiers for fulfilling the safety requirements with the smallest possible energy expenditure for the coolant pumping. The result of shaping the nuclear reactor core with identical cooling channels can be predicted at a quality level with no detailed calculations. Therefore, the selection of the shaping principle in this case is not normally difficult and requires detailed calculations only where the shaping is accompanied by installation of local heat exchange intensifiers. The situation is different if the core has cooling channels of different geometries. In this case, no detailed calculation of the shaping and heat exchange intensifier influence on the temperature field change can be avoided. The paper deals with determination of the variation in the maximum temperatures of the cooling channel walls in high-temperature gas-cooled reactors using, in a combined manner, the effects of the coolant mass flow shaping and the heat exchange intensifier installation in the channels. Different shaping conditions have been considered. The calculated dependences obtained by the authors and the procedure for determining the thermal parameters of the coolant and the maximum temperatures of the heat exchange surface walls in the system of parallel cooling channels were used. The core of the nuclear reactor in the nuclear power system of the GT-MGR design [4 - 6] with cooling channels of different diameters has been calculated for various options. Coolant flow and cooling channel temperature distributions in different shaping conditions have been determined using local resistances and heat exchange intensifiers. The preferred options have been identified providing for the least maximum temperature of the most heated channel wall with the smallest possible core pressure drop. The calculation procedure has been verified by comparing directly the calculation results obtained based on the proposed algorithm with the CFD modeling results [7 - 13].